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sijie pushed a commit to branch master
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The following commit(s) were added to refs/heads/master by this push:
     new 6bf6971  Use immutable metadata in LedgerHandle
6bf6971 is described below

commit 6bf69714ed2e336499bec7d3513773bf8a4f2a02
Author: Ivan Kelly <[email protected]>
AuthorDate: Thu Oct 25 14:28:57 2018 +0200

    Use immutable metadata in LedgerHandle
    
    Which means that for the two LedgerHandle operations that mutate the
    metadata, ensemble change and closing, ensure that metadata is written
    to the metadata store before the client ever uses it.
    
    Master issue: #281
    
    Author: Ivan Kelly <[email protected]>
    Author: Sijie Guo <[email protected]>
    Author: Charan Reddy Guttapalem <[email protected]>
    Author: Andrey Yegorov <[email protected]>
    Author: Samuel Just <[email protected]>
    
    Reviewers: Sijie Guo <[email protected]>, Venkateswararao Jujjuri (JV) 
<None>, Samuel Just <[email protected]>
    
    This closes #1646 from ivankelly/immutable-handle-failures
---
 .../apache/bookkeeper/client/EnsembleUtils.java    |  98 +++
 .../org/apache/bookkeeper/client/LedgerHandle.java | 667 ++++++---------------
 .../apache/bookkeeper/client/LedgerHandleAdv.java  |   6 +-
 .../apache/bookkeeper/client/LedgerMetadata.java   |  22 +-
 .../bookkeeper/client/LedgerMetadataBuilder.java   |  13 +
 .../org/apache/bookkeeper/client/PendingAddOp.java |   8 +-
 .../bookkeeper/client/ReadOnlyLedgerHandle.java    |  82 +--
 .../apache/bookkeeper/client/api/WriteHandle.java  |  16 +
 .../apache/bookkeeper/client/BookKeeperTest.java   |   9 +-
 .../org/apache/bookkeeper/client/ClientUtil.java   |  23 +
 .../apache/bookkeeper/client/DeferredSyncTest.java |   3 +-
 .../bookkeeper/client/HandleFailuresTest.java      | 444 ++++++++++++++
 .../apache/bookkeeper/client/LedgerClose2Test.java | 269 +++++++++
 .../apache/bookkeeper/client/MdcContextTest.java   |   6 +-
 .../client/TestDisableEnsembleChange.java          |   6 +-
 .../client/TestReadLastConfirmedLongPoll.java      |   5 +-
 .../apache/bookkeeper/meta/MockLedgerManager.java  |  95 ++-
 .../apache/bookkeeper/test/ConditionalSetTest.java |  14 +-
 .../java/org/apache/bookkeeper/util/TestUtils.java |  17 +-
 19 files changed, 1157 insertions(+), 646 deletions(-)

diff --git 
a/bookkeeper-server/src/main/java/org/apache/bookkeeper/client/EnsembleUtils.java
 
b/bookkeeper-server/src/main/java/org/apache/bookkeeper/client/EnsembleUtils.java
new file mode 100644
index 0000000..e4ab118
--- /dev/null
+++ 
b/bookkeeper-server/src/main/java/org/apache/bookkeeper/client/EnsembleUtils.java
@@ -0,0 +1,98 @@
+/*
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ *
+ */
+package org.apache.bookkeeper.client;
+
+import static com.google.common.base.Preconditions.checkArgument;
+
+import java.util.ArrayList;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+
+import org.apache.bookkeeper.net.BookieSocketAddress;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+class EnsembleUtils {
+    private static final Logger LOG = 
LoggerFactory.getLogger(EnsembleUtils.class);
+
+    static List<BookieSocketAddress> replaceBookiesInEnsemble(BookieWatcher 
bookieWatcher,
+                                                              LedgerMetadata 
metadata,
+                                                              
List<BookieSocketAddress> oldEnsemble,
+                                                              Map<Integer, 
BookieSocketAddress> failedBookies,
+                                                              String 
logContext)
+            throws BKException.BKNotEnoughBookiesException {
+        List<BookieSocketAddress> newEnsemble = new ArrayList<>(oldEnsemble);
+
+        int ensembleSize = metadata.getEnsembleSize();
+        int writeQ = metadata.getWriteQuorumSize();
+        int ackQ = metadata.getAckQuorumSize();
+        Map<String, byte[]> customMetadata = metadata.getCustomMetadata();
+
+        Set<BookieSocketAddress> exclude = new 
HashSet<>(failedBookies.values());
+
+        int replaced = 0;
+        for (Map.Entry<Integer, BookieSocketAddress> entry : 
failedBookies.entrySet()) {
+            int idx = entry.getKey();
+            BookieSocketAddress addr = entry.getValue();
+            if (LOG.isDebugEnabled()) {
+                LOG.debug("{} replacing bookie: {} index: {}", logContext, 
addr, idx);
+            }
+
+            if (!newEnsemble.get(idx).equals(addr)) {
+                if (LOG.isDebugEnabled()) {
+                    LOG.debug("{} Not changing failed bookie {} at index {}, 
already changed to {}",
+                              logContext, addr, idx, newEnsemble.get(idx));
+                }
+                continue;
+            }
+            try {
+                BookieSocketAddress newBookie = bookieWatcher.replaceBookie(
+                        ensembleSize, writeQ, ackQ, customMetadata, 
newEnsemble, idx, exclude);
+                newEnsemble.set(idx, newBookie);
+
+                replaced++;
+            } catch (BKException.BKNotEnoughBookiesException e) {
+                // if there is no bookie replaced, we throw not enough bookie 
exception
+                if (replaced <= 0) {
+                    throw e;
+                } else {
+                    break;
+                }
+            }
+        }
+        return newEnsemble;
+    }
+
+    static Set<Integer> diffEnsemble(List<BookieSocketAddress> e1,
+                                     List<BookieSocketAddress> e2) {
+        checkArgument(e1.size() == e2.size(), "Ensembles must be of same 
size");
+        Set<Integer> diff = new HashSet<>();
+        for (int i = 0; i < e1.size(); i++) {
+            if (!e1.get(i).equals(e2.get(i))) {
+                diff.add(i);
+            }
+        }
+        return diff;
+    }
+}
diff --git 
a/bookkeeper-server/src/main/java/org/apache/bookkeeper/client/LedgerHandle.java
 
b/bookkeeper-server/src/main/java/org/apache/bookkeeper/client/LedgerHandle.java
index beddaed..a340cc7 100644
--- 
a/bookkeeper-server/src/main/java/org/apache/bookkeeper/client/LedgerHandle.java
+++ 
b/bookkeeper-server/src/main/java/org/apache/bookkeeper/client/LedgerHandle.java
@@ -20,11 +20,12 @@
  */
 package org.apache.bookkeeper.client;
 
+import static com.google.common.base.Preconditions.checkState;
+
 import static 
org.apache.bookkeeper.client.api.BKException.Code.ClientClosedException;
 import static org.apache.bookkeeper.client.api.BKException.Code.WriteException;
 
 import com.google.common.annotations.VisibleForTesting;
-import com.google.common.base.Objects;
 import com.google.common.cache.CacheBuilder;
 import com.google.common.cache.CacheLoader;
 import com.google.common.cache.LoadingCache;
@@ -39,7 +40,6 @@ import java.util.Arrays;
 import java.util.EnumSet;
 import java.util.Enumeration;
 import java.util.HashMap;
-import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
 import java.util.Queue;
@@ -76,12 +76,10 @@ import org.apache.bookkeeper.common.util.MathUtils;
 import org.apache.bookkeeper.net.BookieSocketAddress;
 import org.apache.bookkeeper.proto.BookieProtocol;
 import org.apache.bookkeeper.proto.BookkeeperInternalCallbacks.GenericCallback;
-import org.apache.bookkeeper.proto.DataFormats.LedgerMetadataFormat.State;
 import org.apache.bookkeeper.proto.checksum.DigestManager;
 import org.apache.bookkeeper.stats.Counter;
 import org.apache.bookkeeper.stats.Gauge;
 import org.apache.bookkeeper.stats.OpStatsLogger;
-import org.apache.bookkeeper.util.OrderedGenericCallback;
 import org.apache.bookkeeper.util.SafeRunnable;
 import org.apache.commons.collections4.IteratorUtils;
 import org.slf4j.Logger;
@@ -101,6 +99,13 @@ public class LedgerHandle implements WriteHandle {
     final long ledgerId;
     long lastAddPushed;
 
+    private enum HandleState {
+        OPEN,
+        CLOSED
+    };
+
+    private HandleState handleState = HandleState.OPEN;
+
     /**
       * Last entryId which has been confirmed to be written durably to the 
bookies.
       * This value is used by readers, the the LAC protocol
@@ -123,8 +128,9 @@ public class LedgerHandle implements WriteHandle {
 
     ScheduledFuture<?> timeoutFuture = null;
 
-    private final Map<Integer, BookieSocketAddress> delayedWriteFailedBookies =
-            new HashMap<Integer, BookieSocketAddress>();
+    @VisibleForTesting
+    final Map<Integer, BookieSocketAddress> delayedWriteFailedBookies =
+        new HashMap<Integer, BookieSocketAddress>();
 
     /**
      * Invalid entry id. This value is returned from methods which
@@ -138,7 +144,8 @@ public class LedgerHandle implements WriteHandle {
      */
     public static final long INVALID_LEDGER_ID = -0xABCDABCDL;
 
-    final AtomicInteger blockAddCompletions = new AtomicInteger(0);
+    final Object metadataLock = new Object();
+    boolean changingEnsemble = false;
     final AtomicInteger numEnsembleChanges = new AtomicInteger(0);
     Queue<PendingAddOp> pendingAddOps;
     ExplicitLacFlushPolicy explicitLacFlushPolicy;
@@ -148,10 +155,6 @@ public class LedgerHandle implements WriteHandle {
     final Counter lacUpdateMissesCounter;
     private final OpStatsLogger clientChannelWriteWaitStats;
 
-    public Map<Integer, BookieSocketAddress> getDelayedWriteFailedBookies() {
-        return delayedWriteFailedBookies;
-    }
-
     LedgerHandle(ClientContext clientCtx,
                  long ledgerId, LedgerMetadata metadata,
                  BookKeeper.DigestType digestType, byte[] password,
@@ -468,6 +471,10 @@ public class LedgerHandle implements WriteHandle {
         return getLedgerMetadata().isClosed();
     }
 
+    boolean isHandleWritable() {
+        return !getLedgerMetadata().isClosed() && handleState == 
HandleState.OPEN;
+    }
+
     void asyncCloseInternal(final CloseCallback cb, final Object ctx, final 
int rc) {
         try {
             doAsyncCloseInternal(cb, ctx, rc);
@@ -494,135 +501,75 @@ public class LedgerHandle implements WriteHandle {
         clientCtx.getMainWorkerPool().executeOrdered(ledgerId, new 
SafeRunnable() {
             @Override
             public void safeRun() {
-                final long prevLastEntryId;
-                final long prevLength;
-                final State prevState;
-                List<PendingAddOp> pendingAdds;
-
-                if (isClosed()) {
-                    // TODO: make ledger metadata immutable {@link 
https://github.com/apache/bookkeeper/issues/281}
-                    // Although the metadata is already closed, we don't need 
to proceed zookeeper metadata update, but
-                    // we still need to error out the pending add ops.
-                    //
-                    // There is a race condition a pending add op is enqueued, 
after a close op reset ledger metadata
-                    // state to unclosed to resolve metadata conflicts. If we 
don't error out these pending add ops,
-                    // they would be leak and never callback.
-                    //
-                    // The race condition happen in following sequence:
-                    // a) ledger L is fenced
-                    // b) write entry E encountered LedgerFencedException, 
trigger ledger close procedure
-                    // c) ledger close encountered metadata version exception 
and set ledger metadata back to open
-                    // d) writer tries to write entry E+1, since ledger 
metadata is still open (reset by c))
-                    // e) the close procedure in c) resolved the metadata 
conflicts and set ledger metadata to closed
-                    // f) writing entry E+1 encountered LedgerFencedException 
which will enter ledger close procedure
-                    // g) it would find that ledger metadata is closed, then 
it callbacks immediately without erroring
-                    //    out any pendings
-                    synchronized (LedgerHandle.this) {
-                        pendingAdds = drainPendingAddsToErrorOut();
-                    }
-                    errorOutPendingAdds(rc, pendingAdds);
-                    cb.closeComplete(BKException.Code.OK, LedgerHandle.this, 
ctx);
-                    return;
-                }
+                final HandleState prevHandleState;
+                final List<PendingAddOp> pendingAdds;
+                final long lastEntry;
+                final long finalLength;
 
                 synchronized (LedgerHandle.this) {
-                    LedgerMetadata metadata = getLedgerMetadata();
-                    prevState = metadata.getState();
-                    prevLastEntryId = metadata.getLastEntryId();
-                    prevLength = metadata.getLength();
+                    prevHandleState = handleState;
 
                     // drain pending adds first
-                    pendingAdds = drainPendingAddsToErrorOut();
-
-                    // synchronized on LedgerHandle.this to ensure that
-                    // lastAddPushed can not be updated after the metadata
-                    // is closed.
-                    metadata.setLength(length);
-                    metadata.close(lastAddConfirmed);
-                    lastAddPushed = lastAddConfirmed;
+                    pendingAdds = drainPendingAddsAndAdjustLength();
+
+                    // taking the length must occur after draining, as 
draining changes the length
+                    lastEntry = lastAddPushed = 
LedgerHandle.this.lastAddConfirmed;
+                    finalLength = LedgerHandle.this.length;
+                    handleState = HandleState.CLOSED;
                 }
 
                 // error out all pending adds during closing, the callbacks 
shouldn't be
                 // running under any bk locks.
                 errorOutPendingAdds(rc, pendingAdds);
 
-                if (LOG.isDebugEnabled()) {
-                    LedgerMetadata metadata = getLedgerMetadata();
-                    LOG.debug("Closing ledger: " + ledgerId + " at entryId: "
-                              + metadata.getLastEntryId() + " with this many 
bytes: " + metadata.getLength());
-                }
-
-                final class CloseCb extends 
OrderedGenericCallback<LedgerMetadata> {
-                    CloseCb() {
-                        super(clientCtx.getMainWorkerPool(), ledgerId);
+                if (prevHandleState == HandleState.CLOSED) {
+                    cb.closeComplete(BKException.Code.OK, LedgerHandle.this, 
ctx);
+                } else {
+                    if (LOG.isDebugEnabled()) {
+                        LOG.debug("Closing ledger: {} at entryId {} with {} 
bytes", getId(), lastEntry, finalLength);
                     }
 
-                    @Override
-                    public void safeOperationComplete(final int rc, 
LedgerMetadata writtenMetadata) {
-                        if (rc == BKException.Code.MetadataVersionException) {
-                            rereadMetadata(new 
OrderedGenericCallback<LedgerMetadata>(clientCtx.getMainWorkerPool(),
-                                                                               
       ledgerId) {
-                                @Override
-                                public void safeOperationComplete(int newrc, 
LedgerMetadata newMeta) {
-                                    if (newrc != BKException.Code.OK) {
-                                        LOG.error("Error reading new metadata 
from ledger {} when closing: {}",
-                                                ledgerId, 
BKException.codeLogger(newrc));
-                                        cb.closeComplete(rc, 
LedgerHandle.this, ctx);
+                    tearDownWriteHandleState();
+                    new MetadataUpdateLoop(
+                            clientCtx.getLedgerManager(), getId(),
+                            LedgerHandle.this::getLedgerMetadata,
+                            (metadata) -> {
+                                if (metadata.isClosed()) {
+                                    /* If the ledger has been closed with the 
same lastEntry
+                                     * and length that we planned to close 
with, we have nothing to do,
+                                     * so just return success */
+                                    if (lastEntry == metadata.getLastEntryId()
+                                        && finalLength == 
metadata.getLength()) {
+                                        return false;
                                     } else {
-                                        LedgerMetadata metadata = 
getLedgerMetadata();
-                                        metadata.setState(prevState);
-                                        if (prevState.equals(State.CLOSED)) {
-                                            metadata.close(prevLastEntryId);
-                                        }
-
-                                        metadata.setLength(prevLength);
-                                        if (!metadata.isNewerThan(newMeta)
-                                                && 
!metadata.isConflictWith(newMeta)) {
-                                            // use the new metadata's 
ensemble, in case re-replication already
-                                            // replaced some bookies in the 
ensemble.
-                                            
metadata.setEnsembles(newMeta.getEnsembles());
-                                            
metadata.setVersion(newMeta.version);
-                                            metadata.setLength(length);
-                                            
metadata.close(getLastAddConfirmed());
-                                            writeLedgerConfig(new CloseCb());
-                                            return;
-                                        } else {
-                                            metadata.setLength(length);
-                                            
metadata.close(getLastAddConfirmed());
-                                            LOG.warn("Conditional update 
ledger metadata for ledger {} failed.",
-                                                    ledgerId);
-                                            cb.closeComplete(rc, 
LedgerHandle.this, ctx);
-                                        }
+                                        LOG.error("Metadata conflict when 
closing ledger {}."
+                                                  + " Another client may have 
recovered the ledger while there"
+                                                  + " were writes outstanding. 
(local lastEntry:{} length:{}) "
+                                                  + " (metadata lastEntry:{} 
length:{})",
+                                                  getId(), lastEntry, 
finalLength,
+                                                  metadata.getLastEntryId(), 
metadata.getLength());
+                                        throw new 
BKException.BKMetadataVersionException();
                                     }
+                                } else {
+                                    return true;
                                 }
-
-                                @Override
-                                public String toString() {
-                                    return 
String.format("ReReadMetadataForClose(%d)", ledgerId);
+                            },
+                            (metadata) -> {
+                                return LedgerMetadataBuilder.from(metadata)
+                                    .closingAt(lastEntry, finalLength).build();
+                            },
+                            LedgerHandle.this::setLedgerMetadata)
+                        .run().whenComplete((metadata, ex) -> {
+                                if (ex != null) {
+                                    cb.closeComplete(
+                                            BKException.getExceptionCode(
+                                                    ex, 
BKException.Code.UnexpectedConditionException),
+                                            LedgerHandle.this, ctx);
+                                } else {
+                                    cb.closeComplete(BKException.Code.OK, 
LedgerHandle.this, ctx);
                                 }
-                            });
-                        } else if (rc != BKException.Code.OK) {
-                            LOG.error("Error update ledger metadata for ledger 
{} : {}",
-                                    ledgerId, BKException.codeLogger(rc));
-                            cb.closeComplete(rc, LedgerHandle.this, ctx);
-                        } else {
-                            cb.closeComplete(BKException.Code.OK, 
LedgerHandle.this, ctx);
-                        }
-                    }
-
-                    @Override
-                    public String toString() {
-                        return String.format("WriteLedgerConfigForClose(%d)", 
ledgerId);
-                    }
+                        });
                 }
-
-                writeLedgerConfig(new CloseCb());
-                tearDownWriteHandleState();
-            }
-
-            @Override
-            public String toString() {
-                return String.format("CloseLedgerHandle(%d)", ledgerId);
             }
         });
     }
@@ -1133,7 +1080,7 @@ public class LedgerHandle implements WriteHandle {
             // synchronized on this to ensure that
             // the ledger isn't closed between checking and
             // updating lastAddPushed
-            if (getLedgerMetadata().isClosed()) {
+            if (!isHandleWritable()) {
                 wasClosed = true;
             }
         }
@@ -1292,14 +1239,14 @@ public class LedgerHandle implements WriteHandle {
             // synchronized on this to ensure that
             // the ledger isn't closed between checking and
             // updating lastAddPushed
-            if (getLedgerMetadata().isClosed()) {
-                wasClosed = true;
-            } else {
+            if (isHandleWritable()) {
                 long entryId = ++lastAddPushed;
                 long currentLedgerLength = 
addToLength(op.payload.readableBytes());
                 op.setEntryId(entryId);
                 op.setLedgerLength(currentLedgerLength);
                 pendingAddOps.add(op);
+            } else {
+                wasClosed = true;
             }
         }
 
@@ -1755,10 +1702,10 @@ public class LedgerHandle implements WriteHandle {
     }
 
     void errorOutPendingAdds(int rc) {
-        errorOutPendingAdds(rc, drainPendingAddsToErrorOut());
+        errorOutPendingAdds(rc, drainPendingAddsAndAdjustLength());
     }
 
-    synchronized List<PendingAddOp> drainPendingAddsToErrorOut() {
+    synchronized List<PendingAddOp> drainPendingAddsAndAdjustLength() {
         PendingAddOp pendingAddOp;
         List<PendingAddOp> opsDrained = new 
ArrayList<PendingAddOp>(pendingAddOps.size());
         while ((pendingAddOp = pendingAddOps.poll()) != null) {
@@ -1780,7 +1727,7 @@ public class LedgerHandle implements WriteHandle {
         PendingAddOp pendingAddOp;
 
         while ((pendingAddOp = pendingAddOps.peek()) != null
-               && blockAddCompletions.get() == 0) {
+               && !changingEnsemble) {
             if (!pendingAddOp.completed) {
                 if (LOG.isDebugEnabled()) {
                     LOG.debug("pending add not completed: {}", pendingAddOp);
@@ -1808,77 +1755,35 @@ public class LedgerHandle implements WriteHandle {
 
     }
 
-    EnsembleInfo replaceBookieInMetadata(final Map<Integer, 
BookieSocketAddress> failedBookies,
-                                         int ensembleChangeIdx)
-            throws BKException.BKNotEnoughBookiesException {
-        final ArrayList<BookieSocketAddress> newEnsemble = new 
ArrayList<BookieSocketAddress>();
-        final long newEnsembleStartEntry = getLastAddConfirmed() + 1;
-        final HashSet<Integer> replacedBookies = new HashSet<Integer>();
-        final LedgerMetadata metadata = getLedgerMetadata();
-        synchronized (metadata) {
-            newEnsemble.addAll(getCurrentEnsemble());
-            for (Map.Entry<Integer, BookieSocketAddress> entry : 
failedBookies.entrySet()) {
-                int idx = entry.getKey();
-                BookieSocketAddress addr = entry.getValue();
-                if (LOG.isDebugEnabled()) {
-                    LOG.debug("[EnsembleChange-L{}-{}] : replacing bookie: {} 
index: {}",
-                            getId(), ensembleChangeIdx, addr, idx);
-                }
-                if (!newEnsemble.get(idx).equals(addr)) {
-                    // ensemble has already changed, failure of this addr is 
immaterial
-                    if (LOG.isDebugEnabled()) {
-                        LOG.debug("Write did not succeed to {}, bookieIndex 
{}, but we have already fixed it.",
-                                  addr, idx);
-                    }
-                    continue;
-                }
-                try {
-                    BookieSocketAddress newBookie = 
clientCtx.getBookieWatcher().replaceBookie(
-                        metadata.getEnsembleSize(),
-                        metadata.getWriteQuorumSize(),
-                        metadata.getAckQuorumSize(),
-                        metadata.getCustomMetadata(),
-                        newEnsemble,
-                        idx,
-                        new 
HashSet<BookieSocketAddress>(failedBookies.values()));
-                    newEnsemble.set(idx, newBookie);
-                    replacedBookies.add(idx);
-                } catch (BKException.BKNotEnoughBookiesException e) {
-                    // if there is no bookie replaced, we throw not enough 
bookie exception
-                    if (replacedBookies.size() <= 0) {
-                        throw e;
-                    } else {
-                        break;
-                    }
-                }
-            }
-            if (LOG.isDebugEnabled()) {
-                LOG.debug("[EnsembleChange-L{}-{}] : changing ensemble from: 
{} to: {} starting at entry: {},"
-                    + " failed bookies: {}, replaced bookies: {}",
-                        ledgerId, ensembleChangeIdx, getCurrentEnsemble(), 
newEnsemble,
-                        (getLastAddConfirmed() + 1), failedBookies, 
replacedBookies);
-            }
-            metadata.addEnsemble(newEnsembleStartEntry, newEnsemble);
+    @VisibleForTesting
+    boolean hasDelayedWriteFailedBookies() {
+        return !delayedWriteFailedBookies.isEmpty();
+    }
+
+    void notifyWriteFailed(int index, BookieSocketAddress addr) {
+        synchronized (metadataLock) {
+            delayedWriteFailedBookies.put(index, addr);
         }
-        return new EnsembleInfo(newEnsemble, failedBookies, replacedBookies);
     }
 
-    void handleDelayedWriteBookieFailure() {
-        final Map<Integer, BookieSocketAddress> copyDelayedWriteFailedBookies =
-                new HashMap<Integer, 
BookieSocketAddress>(delayedWriteFailedBookies);
-        delayedWriteFailedBookies.clear();
+    void maybeHandleDelayedWriteBookieFailure() {
+        synchronized (metadataLock) {
+            if (delayedWriteFailedBookies.isEmpty()) {
+                return;
+            }
+            Map<Integer, BookieSocketAddress> toReplace = new 
HashMap<>(delayedWriteFailedBookies);
+            delayedWriteFailedBookies.clear();
 
-        // Original intent of this change is to do a best-effort ensemble 
change.
-        // But this is not possible until the local metadata is completely 
immutable.
-        // Until the feature "Make LedgerMetadata Immutable #610" Is complete 
we will use
-        // handleBookieFailure() to handle delayed writes as regular bookie 
failures.
-        handleBookieFailure(copyDelayedWriteFailedBookies);
+            // Original intent of this change is to do a best-effort ensemble 
change.
+            // But this is not possible until the local metadata is completely 
immutable.
+            // Until the feature "Make LedgerMetadata Immutable #610" Is 
complete we will use
+            // handleBookieFailure() to handle delayed writes as regular 
bookie failures.
+            handleBookieFailure(toReplace);
+        }
     }
 
     void handleBookieFailure(final Map<Integer, BookieSocketAddress> 
failedBookies) {
-        int curBlockAddCompletions = blockAddCompletions.incrementAndGet();
         if (clientCtx.getConf().disableEnsembleChangeFeature.isAvailable()) {
-            blockAddCompletions.decrementAndGet();
             if (LOG.isDebugEnabled()) {
                 LOG.debug("Ensemble change is disabled. Retry sending to 
failed bookies {} for ledger {}.",
                     failedBookies, ledgerId);
@@ -1888,7 +1793,6 @@ public class LedgerHandle implements WriteHandle {
         }
 
         if (writeFlags.contains(WriteFlag.DEFERRED_SYNC)) {
-            blockAddCompletions.decrementAndGet();
             if (LOG.isDebugEnabled()) {
                 LOG.debug("Cannot perform ensemble change with write flags {}. 
"
                         + "Failed bookies {} for ledger {}.",
@@ -1898,302 +1802,113 @@ public class LedgerHandle implements WriteHandle {
             return;
         }
 
-        int curNumEnsembleChanges = numEnsembleChanges.incrementAndGet();
 
-        // when the ensemble changes are too frequent, close handle
-        if (curNumEnsembleChanges > 
clientCtx.getConf().maxAllowedEnsembleChanges) {
-            if (LOG.isDebugEnabled()) {
-                LOG.debug("Ledger {} reaches max allowed ensemble change 
number {}",
-                          ledgerId, 
clientCtx.getConf().maxAllowedEnsembleChanges);
-            }
-            handleUnrecoverableErrorDuringAdd(WriteException);
-            return;
-        }
-        LedgerMetadata metadata = getLedgerMetadata();
-        synchronized (metadata) {
-            try {
-                EnsembleInfo ensembleInfo = 
replaceBookieInMetadata(failedBookies, curNumEnsembleChanges);
-                if (ensembleInfo.replacedBookies.isEmpty()) {
-                    blockAddCompletions.decrementAndGet();
-                    return;
-                }
-                if (LOG.isDebugEnabled()) {
-                    LOG.debug("[EnsembleChange-L{}-{}] : writing new ensemble 
info = {}, block add completions = {}",
-                            getId(), curNumEnsembleChanges, ensembleInfo, 
curBlockAddCompletions);
-                }
-                writeLedgerConfig(new ChangeEnsembleCb(ensembleInfo, 
curBlockAddCompletions,
-                        curNumEnsembleChanges));
-                // clear if there are any delayed write failures were recorded.
-                delayedWriteFailedBookies.clear();
-            } catch (BKException.BKNotEnoughBookiesException e) {
-                LOG.error("Could not get additional bookie to remake ensemble, 
closing ledger: {}", ledgerId);
-                handleUnrecoverableErrorDuringAdd(e.getCode());
-                return;
-            }
-        }
-    }
-
-    // Contains newly reformed ensemble, bookieIndex, failedBookieAddress
-    static final class EnsembleInfo {
-        final ArrayList<BookieSocketAddress> newEnsemble;
-        private final Map<Integer, BookieSocketAddress> failedBookies;
-        final Set<Integer> replacedBookies;
-
-        public EnsembleInfo(ArrayList<BookieSocketAddress> newEnsemble,
-                            Map<Integer, BookieSocketAddress> failedBookies,
-                            Set<Integer> replacedBookies) {
-            this.newEnsemble = newEnsemble;
-            this.failedBookies = failedBookies;
-            this.replacedBookies = replacedBookies;
-        }
-
-        @Override
-        public String toString() {
-            StringBuilder sb = new StringBuilder();
-            sb.append("Ensemble Info : failed bookies = 
").append(failedBookies)
-                    .append(", replaced bookies = ").append(replacedBookies)
-                    .append(", new ensemble = ").append(newEnsemble);
-            return sb.toString();
-        }
-    }
-
-    /**
-     * Callback which is updating the ledgerMetadata in zk with the newly
-     * reformed ensemble. On MetadataVersionException, will reread latest
-     * ledgerMetadata and act upon.
-     */
-    private final class ChangeEnsembleCb extends 
OrderedGenericCallback<LedgerMetadata> {
-        private final EnsembleInfo ensembleInfo;
-        private final int curBlockAddCompletions;
-        private final int ensembleChangeIdx;
-
-        ChangeEnsembleCb(EnsembleInfo ensembleInfo,
-                         int curBlockAddCompletions,
-                         int ensembleChangeIdx) {
-            super(clientCtx.getMainWorkerPool(), ledgerId);
-            this.ensembleInfo = ensembleInfo;
-            this.curBlockAddCompletions = curBlockAddCompletions;
-            this.ensembleChangeIdx = ensembleChangeIdx;
-        }
-
-        @Override
-        public void safeOperationComplete(final int rc, LedgerMetadata 
writtenMetadata) {
-            if (rc == BKException.Code.MetadataVersionException) {
-                // We changed the ensemble, but got a version exception. We
-                // should still consider this as an ensemble change
-                ensembleChangeCounter.inc();
-
-                if (LOG.isDebugEnabled()) {
-                    LOG.info("[EnsembleChange-L{}-{}] : encountered version 
conflicts, re-read ledger metadata.",
-                        getId(), ensembleChangeIdx);
-                }
-
-                rereadMetadata(new ReReadLedgerMetadataCb(rc,
-                                       ensembleInfo, curBlockAddCompletions, 
ensembleChangeIdx));
-                return;
-            } else if (rc != BKException.Code.OK) {
-                LOG.error("[EnsembleChange-L{}-{}] : could not persist ledger 
metadata : info = {}, "
-                        + "closing ledger : {}.", getId(), ensembleChangeIdx, 
ensembleInfo, rc);
-                handleUnrecoverableErrorDuringAdd(rc);
-                return;
-            }
-            int newBlockAddCompletions = blockAddCompletions.decrementAndGet();
+        boolean triggerLoop = false;
+        Map<Integer, BookieSocketAddress> toReplace = null;
+        List<BookieSocketAddress> origEnsemble = null;
+        synchronized (metadataLock) {
+            if (changingEnsemble) {
+                delayedWriteFailedBookies.putAll(failedBookies);
+            } else {
+                changingEnsemble = true;
+                triggerLoop = true;
 
+                toReplace = new HashMap<>(delayedWriteFailedBookies);
+                delayedWriteFailedBookies.clear();
+                toReplace.putAll(failedBookies);
 
-            if (LOG.isDebugEnabled()) {
-                LOG.info("[EnsembleChange-L{}-{}] : completed ensemble change, 
block add completion {} => {}",
-                        getId(), ensembleChangeIdx, curBlockAddCompletions, 
newBlockAddCompletions);
+                origEnsemble = getCurrentEnsemble();
             }
-
-            // We've successfully changed an ensemble
-            ensembleChangeCounter.inc();
-            LOG.info("New Ensemble: {} for ledger: {}", 
ensembleInfo.newEnsemble, ledgerId);
-
-            // the failed bookie has been replaced
-            unsetSuccessAndSendWriteRequest(ensembleInfo.newEnsemble, 
ensembleInfo.replacedBookies);
         }
-
-        @Override
-        public String toString() {
-            return String.format("ChangeEnsemble(%d)", ledgerId);
+        if (triggerLoop) {
+            ensembleChangeLoop(origEnsemble, toReplace);
         }
     }
 
-    /**
-     * Callback which is reading the ledgerMetadata present in zk. This will 
try
-     * to resolve the version conflicts.
-     */
-    private final class ReReadLedgerMetadataCb extends 
OrderedGenericCallback<LedgerMetadata> {
-        private final int rc;
-        private final EnsembleInfo ensembleInfo;
-        private final int curBlockAddCompletions;
-        private final int ensembleChangeIdx;
-
-        ReReadLedgerMetadataCb(int rc,
-                               EnsembleInfo ensembleInfo,
-                               int curBlockAddCompletions,
-                               int ensembleChangeIdx) {
-            super(clientCtx.getMainWorkerPool(), ledgerId);
-            this.rc = rc;
-            this.ensembleInfo = ensembleInfo;
-            this.curBlockAddCompletions = curBlockAddCompletions;
-            this.ensembleChangeIdx = ensembleChangeIdx;
-        }
+    void ensembleChangeLoop(List<BookieSocketAddress> origEnsemble, 
Map<Integer, BookieSocketAddress> failedBookies) {
+        int ensembleChangeId = numEnsembleChanges.incrementAndGet();
+        String logContext = String.format("[EnsembleChange(ledger:%d, 
change-id:%010d)]", ledgerId, ensembleChangeId);
 
-        @Override
-        public void safeOperationComplete(int newrc, LedgerMetadata newMeta) {
-            if (newrc != BKException.Code.OK) {
-                LOG.error("[EnsembleChange-L{}-{}] : error re-reading metadata 
"
-                                + "to address ensemble change conflicts: {}",
-                        ledgerId, ensembleChangeIdx, 
BKException.codeLogger(newrc));
-                handleUnrecoverableErrorDuringAdd(rc);
-            } else {
-                if (!resolveConflict(newMeta)) {
-                    LOG.error("[EnsembleChange-L{}-{}] : could not resolve 
ledger metadata conflict"
-                                    + " while changing ensemble to: {}, local 
meta data is \n {} \n,"
-                                    + " zk meta data is \n {} \n, closing 
ledger",
-                            ledgerId, ensembleChangeIdx, 
ensembleInfo.newEnsemble, getLedgerMetadata(), newMeta);
-                    handleUnrecoverableErrorDuringAdd(rc);
-                }
-            }
+        // when the ensemble changes are too frequent, close handle
+        if (ensembleChangeId > clientCtx.getConf().maxAllowedEnsembleChanges) {
+            LOG.info("{} reaches max allowed ensemble change number {}",
+                     logContext, 
clientCtx.getConf().maxAllowedEnsembleChanges);
+            handleUnrecoverableErrorDuringAdd(WriteException);
+            return;
         }
 
-        /**
-         * Specific resolve conflicts happened when multiple bookies failures 
in same ensemble.
-         *
-         * <p>Resolving the version conflicts between local ledgerMetadata and 
zk
-         * ledgerMetadata. This will do the following:
-         * <ul>
-         * <li>
-         * check whether ledgerMetadata state matches of local and zk</li>
-         * <li>
-         * if the zk ledgerMetadata still contains the failed bookie, then
-         * update zookeeper with the newBookie otherwise send write 
request</li>
-         * </ul>
-         * </p>
-         */
-        private boolean resolveConflict(LedgerMetadata newMeta) {
-            LedgerMetadata metadata = getLedgerMetadata();
-            if (LOG.isDebugEnabled()) {
-                LOG.debug("[EnsembleChange-L{}-{}] : resolving conflicts - 
local metadata = \n {} \n,"
-                    + " zk metadata = \n {} \n", ledgerId, ensembleChangeIdx, 
metadata, newMeta);
-            }
-            // make sure the ledger isn't closed by other ones.
-            if (metadata.getState() != newMeta.getState()) {
-                if (LOG.isDebugEnabled()) {
-                    LOG.info("[EnsembleChange-L{}-{}] : resolving conflicts 
but state changed,"
-                            + " local metadata = \n {} \n, zk metadata = \n {} 
\n",
-                            ledgerId, ensembleChangeIdx, metadata, newMeta);
-                }
-                return false;
-            }
-
-            // We should check number of ensembles since there are two kinds 
of metadata conflicts:
-            // - Case 1: Multiple bookies involved in ensemble change.
-            //           Number of ensembles should be same in this case.
-            // - Case 2: Recovery (Auto/Manually) replaced ensemble and 
ensemble changed.
-            //           The metadata changed due to ensemble change would 
have one more ensemble
-            //           than the metadata changed by recovery.
-            int diff = newMeta.getEnsembles().size() - 
metadata.getEnsembles().size();
-            if (0 != diff) {
-                if (LOG.isDebugEnabled()) {
-                    LOG.debug("[EnsembleChange-L{}-{}] : resolving conflicts 
but ensembles have {} differences,"
-                            + " local metadata = \n {} \n, zk metadata = \n {} 
\n",
-                            ledgerId, ensembleChangeIdx, diff, metadata, 
newMeta);
-                }
-                if (-1 == diff) {
-                    // Case 1: metadata is changed by other ones (e.g. 
Recovery)
-                    return updateMetadataIfPossible(metadata, newMeta);
-                }
-                return false;
-            }
-
-            //
-            // Case 2:
-            //
-            // If the failed the bookie is still existed in the metadata (in 
zookeeper), it means that
-            // the ensemble change of the failed bookie is failed due to 
metadata conflicts. so try to
-            // update the ensemble change metadata again. Otherwise, it means 
that the ensemble change
-            // is already succeed, unset the success and re-adding entries.
-            if (!areFailedBookiesReplaced(newMeta, ensembleInfo)) {
-                // If the in-memory data doesn't contains the failed bookie, 
it means the ensemble change
-                // didn't finish, so try to resolve conflicts with the 
metadata read from zookeeper and
-                // update ensemble changed metadata again.
-                if (areFailedBookiesReplaced(metadata, ensembleInfo)) {
-                    return updateMetadataIfPossible(metadata, newMeta);
-                }
-            } else {
-                ensembleChangeCounter.inc();
-                // We've successfully changed an ensemble
-                // the failed bookie has been replaced
-                int newBlockAddCompletions = 
blockAddCompletions.decrementAndGet();
-                unsetSuccessAndSendWriteRequest(ensembleInfo.newEnsemble, 
ensembleInfo.replacedBookies);
-                if (LOG.isDebugEnabled()) {
-                    LOG.info("[EnsembleChange-L{}-{}] : resolved conflicts, 
block add complectiosn {} => {}.",
-                            ledgerId, ensembleChangeIdx, 
curBlockAddCompletions, newBlockAddCompletions);
-                }
-            }
-            return true;
-        }
+        if (LOG.isDebugEnabled()) {
+            LOG.debug("{} Replacing {} in {}", logContext, failedBookies, 
origEnsemble);
+        }
+
+        AtomicInteger attempts = new AtomicInteger(0);
+        new MetadataUpdateLoop(
+                clientCtx.getLedgerManager(), getId(),
+                this::getLedgerMetadata,
+                (metadata) -> !metadata.isClosed() && !metadata.isInRecovery()
+                        && failedBookies.entrySet().stream().anyMatch(
+                                (e) -> 
metadata.getLastEnsembleValue().get(e.getKey()).equals(e.getValue())),
+                (metadata) -> {
+                    attempts.incrementAndGet();
+
+                    List<BookieSocketAddress> currentEnsemble = 
getCurrentEnsemble();
+                    List<BookieSocketAddress> newEnsemble = 
EnsembleUtils.replaceBookiesInEnsemble(
+                            clientCtx.getBookieWatcher(), metadata, 
currentEnsemble, failedBookies, logContext);
+                    Long lastEnsembleKey = metadata.getLastEnsembleKey();
+                    LedgerMetadataBuilder builder = 
LedgerMetadataBuilder.from(metadata);
+                    long newEnsembleStartEntry = getLastAddConfirmed() + 1;
+                    checkState(lastEnsembleKey <= newEnsembleStartEntry,
+                               "New ensemble must either replace the last 
ensemble, or add a new one");
+                    if (LOG.isDebugEnabled()) {
+                        LOG.debug("{}[attempt:{}] changing ensemble from: {} 
to: {} starting at entry: {}",
+                                  logContext, attempts.get(), currentEnsemble, 
newEnsemble, newEnsembleStartEntry);
+                    }
 
-        /**
-         * Check whether all the failed bookies are replaced.
-         *
-         * @param newMeta
-         *          new ledger metadata
-         * @param ensembleInfo
-         *          ensemble info used for ensemble change.
-         * @return true if all failed bookies are replaced, false otherwise
-         */
-        private boolean areFailedBookiesReplaced(LedgerMetadata newMeta, 
EnsembleInfo ensembleInfo) {
-            boolean replaced = true;
-            for (Integer replacedBookieIdx : ensembleInfo.replacedBookies) {
-                BookieSocketAddress failedBookieAddr = 
ensembleInfo.failedBookies.get(replacedBookieIdx);
-                BookieSocketAddress replacedBookieAddr = newMeta.getEnsembles()
-                    .lastEntry().getValue().get(replacedBookieIdx);
-                replaced &= !Objects.equal(replacedBookieAddr, 
failedBookieAddr);
-            }
-            return replaced;
-        }
+                    if (lastEnsembleKey.equals(newEnsembleStartEntry)) {
+                        return 
builder.replaceEnsembleEntry(newEnsembleStartEntry, newEnsemble).build();
+                    } else {
+                        return builder.newEnsembleEntry(newEnsembleStartEntry, 
newEnsemble).build();
+                    }
+                },
+                this::setLedgerMetadata)
+            .run().whenCompleteAsync((metadata, ex) -> {
+                    if (ex != null) {
+                        LOG.warn("{}[attempt:{}] Exception changing ensemble", 
logContext, attempts.get(), ex);
+                        
handleUnrecoverableErrorDuringAdd(BKException.getExceptionCode(ex, 
WriteException));
+                    } else if (metadata.isClosed()) {
+                        if (LOG.isDebugEnabled()) {
+                            LOG.debug("{}[attempt:{}] Metadata closed during 
attempt to replace bookie."
+                                      + " Another client must have recovered 
the ledger.", logContext, attempts.get());
+                        }
+                        
handleUnrecoverableErrorDuringAdd(BKException.Code.LedgerClosedException);
+                    } else if (metadata.isInRecovery()) {
+                        if (LOG.isDebugEnabled()) {
+                            LOG.debug("{}[attempt:{}] Metadata marked as 
in-recovery during attempt to replace bookie."
+                                      + " Another client must be recovering 
the ledger.", logContext, attempts.get());
+                        }
 
-        private boolean updateMetadataIfPossible(LedgerMetadata metadata, 
LedgerMetadata newMeta) {
-            // if the local metadata is newer than zookeeper metadata, it 
means that metadata is updated
-            // again when it was trying re-reading the metatada, re-kick the 
reread again
-            if (metadata.isNewerThan(newMeta)) {
-                if (LOG.isDebugEnabled()) {
-                    LOG.debug("[EnsembleChange-L{}-{}] : reread metadata 
because local metadata is newer.",
-                        new Object[]{ledgerId, ensembleChangeIdx});
-                }
-                rereadMetadata(this);
-                return true;
-            }
-            // make sure the metadata doesn't changed by other ones.
-            if (metadata.isConflictWith(newMeta)) {
-                if (LOG.isDebugEnabled()) {
-                    LOG.debug("[EnsembleChange-L{}-{}] : metadata is 
conflicted, local metadata = \n {} \n,"
-                        + " zk metadata = \n {} \n", ledgerId, 
ensembleChangeIdx, metadata, newMeta);
-                }
-                return false;
-            }
-            if (LOG.isDebugEnabled()) {
-                LOG.info("[EnsembleChange-L{}-{}] : resolved ledger metadata 
conflict and writing to zookeeper,"
-                        + " local meta data is \n {} \n, zk meta data is \n 
{}.",
-                        ledgerId, ensembleChangeIdx, metadata, newMeta);
-            }
-            // update znode version
-            metadata.setVersion(newMeta.getVersion());
-            // merge ensemble infos from new meta except last ensemble
-            // since they might be modified by recovery tool.
-            metadata.mergeEnsembles(newMeta.getEnsembles());
-            writeLedgerConfig(new ChangeEnsembleCb(ensembleInfo, 
curBlockAddCompletions,
-                    ensembleChangeIdx));
-            return true;
-        }
+                        
handleUnrecoverableErrorDuringAdd(BKException.Code.LedgerFencedException);
+                    } else {
+                        if (LOG.isDebugEnabled()) {
+                            LOG.debug("{}[attempt:{}] Success updating 
metadata.", logContext, attempts.get());
+                        }
 
-        @Override
-        public String toString() {
-            return String.format("ReReadLedgerMetadata(%d)", ledgerId);
-        }
+                        synchronized (metadataLock) {
+                            if (!delayedWriteFailedBookies.isEmpty()) {
+                                Map<Integer, BookieSocketAddress> toReplace = 
new HashMap<>(delayedWriteFailedBookies);
+                                delayedWriteFailedBookies.clear();
+
+                                ensembleChangeLoop(origEnsemble, toReplace);
+                            } else {
+                                List<BookieSocketAddress> newEnsemble = 
getCurrentEnsemble();
+                                Set<Integer> replaced = 
EnsembleUtils.diffEnsemble(origEnsemble, newEnsemble);
+                                LOG.info("New Ensemble: {} for ledger: {}", 
newEnsemble, ledgerId);
+                                unsetSuccessAndSendWriteRequest(newEnsemble, 
replaced);
+                                changingEnsemble = false;
+                            }
+                        }
+                    }
+            }, clientCtx.getMainWorkerPool().chooseThread(ledgerId));
     }
 
     void unsetSuccessAndSendWriteRequest(List<BookieSocketAddress> ensemble, 
final Set<Integer> bookies) {
diff --git 
a/bookkeeper-server/src/main/java/org/apache/bookkeeper/client/LedgerHandleAdv.java
 
b/bookkeeper-server/src/main/java/org/apache/bookkeeper/client/LedgerHandleAdv.java
index c1d3849..bd8beae 100644
--- 
a/bookkeeper-server/src/main/java/org/apache/bookkeeper/client/LedgerHandleAdv.java
+++ 
b/bookkeeper-server/src/main/java/org/apache/bookkeeper/client/LedgerHandleAdv.java
@@ -222,12 +222,12 @@ public class LedgerHandleAdv extends LedgerHandle 
implements WriteAdvHandle {
             // synchronized on this to ensure that
             // the ledger isn't closed between checking and
             // updating lastAddPushed
-            if (getLedgerMetadata().isClosed()) {
-                wasClosed = true;
-            } else {
+            if (isHandleWritable()) {
                 long currentLength = addToLength(op.payload.readableBytes());
                 op.setLedgerLength(currentLength);
                 pendingAddOps.add(op);
+            } else {
+                wasClosed = true;
             }
         }
 
diff --git 
a/bookkeeper-server/src/main/java/org/apache/bookkeeper/client/LedgerMetadata.java
 
b/bookkeeper-server/src/main/java/org/apache/bookkeeper/client/LedgerMetadata.java
index ffb0d6a..8c5e3b8 100644
--- 
a/bookkeeper-server/src/main/java/org/apache/bookkeeper/client/LedgerMetadata.java
+++ 
b/bookkeeper-server/src/main/java/org/apache/bookkeeper/client/LedgerMetadata.java
@@ -19,6 +19,7 @@ package org.apache.bookkeeper.client;
 
 import static com.google.common.base.Charsets.UTF_8;
 import static com.google.common.base.Preconditions.checkArgument;
+import static com.google.common.base.Preconditions.checkState;
 
 import com.google.common.annotations.VisibleForTesting;
 import com.google.common.base.Optional;
@@ -148,9 +149,14 @@ public class LedgerMetadata implements 
org.apache.bookkeeper.client.api.LedgerMe
         this.writeQuorumSize = writeQuorumSize;
         this.ackQuorumSize = ackQuorumSize;
         this.state = state;
-        lastEntryId.ifPresent((eid) -> this.lastEntryId = eid);
+        if (lastEntryId.isPresent()) {
+            this.lastEntryId = lastEntryId.get();
+        } else {
+            this.lastEntryId = LedgerHandle.INVALID_ENTRY_ID;
+        }
         length.ifPresent((l) -> this.length = l);
         setEnsembles(ensembles);
+
         if (state != LedgerMetadataFormat.State.CLOSED) {
             currentEnsemble = this.ensembles.lastEntry().getValue();
         }
@@ -788,11 +794,13 @@ public class LedgerMetadata implements 
org.apache.bookkeeper.client.api.LedgerMe
         return bookies;
     }
 
-    java.util.Optional<Long> getLastEnsembleKey() {
-        if (ensembles.size() > 0) {
-            return java.util.Optional.of(ensembles.lastKey());
-        } else {
-            return java.util.Optional.empty();
-        }
+    List<BookieSocketAddress> getLastEnsembleValue() {
+        checkState(!ensembles.isEmpty(), "Metadata should never be created 
with no ensembles");
+        return ensembles.lastEntry().getValue();
+    }
+
+    Long getLastEnsembleKey() {
+        checkState(!ensembles.isEmpty(), "Metadata should never be created 
with no ensembles");
+        return ensembles.lastKey();
     }
 }
diff --git 
a/bookkeeper-server/src/main/java/org/apache/bookkeeper/client/LedgerMetadataBuilder.java
 
b/bookkeeper-server/src/main/java/org/apache/bookkeeper/client/LedgerMetadataBuilder.java
index a9d83b0..ae78d5f 100644
--- 
a/bookkeeper-server/src/main/java/org/apache/bookkeeper/client/LedgerMetadataBuilder.java
+++ 
b/bookkeeper-server/src/main/java/org/apache/bookkeeper/client/LedgerMetadataBuilder.java
@@ -102,6 +102,19 @@ class LedgerMetadataBuilder {
         return this;
     }
 
+    LedgerMetadataBuilder withWriteQuorumSize(int writeQuorumSize) {
+        checkArgument(ensembleSize >= writeQuorumSize, "Write quorum must be 
less or equal to ensemble size");
+        checkArgument(writeQuorumSize >= ackQuorumSize, "Write quorum must be 
greater or equal to ack quorum");
+        this.writeQuorumSize = writeQuorumSize;
+        return this;
+    }
+
+    LedgerMetadataBuilder withAckQuorumSize(int ackQuorumSize) {
+        checkArgument(writeQuorumSize >= ackQuorumSize, "Ack quorum must be 
less or equal to write quorum");
+        this.ackQuorumSize = ackQuorumSize;
+        return this;
+    }
+
     LedgerMetadataBuilder newEnsembleEntry(long firstEntry, 
List<BookieSocketAddress> ensemble) {
         checkArgument(ensemble.size() == ensembleSize,
                       "Size of passed in ensemble must match the ensembleSize 
of the builder");
diff --git 
a/bookkeeper-server/src/main/java/org/apache/bookkeeper/client/PendingAddOp.java
 
b/bookkeeper-server/src/main/java/org/apache/bookkeeper/client/PendingAddOp.java
index 89bf0b8..ad2f7ae 100644
--- 
a/bookkeeper-server/src/main/java/org/apache/bookkeeper/client/PendingAddOp.java
+++ 
b/bookkeeper-server/src/main/java/org/apache/bookkeeper/client/PendingAddOp.java
@@ -251,10 +251,8 @@ class PendingAddOp extends SafeRunnable implements 
WriteCallback {
 
         // We are about to send. Check if we need to make an ensemble change
         // becasue of delayed write errors
-        Map <Integer, BookieSocketAddress> delayedWriteFailedBookies = 
lh.getDelayedWriteFailedBookies();
-        if (!delayedWriteFailedBookies.isEmpty()) {
-            lh.handleDelayedWriteBookieFailure();
-        }
+        lh.maybeHandleDelayedWriteBookieFailure();
+
         // Iterate over set and trigger the sendWriteRequests
         DistributionSchedule.WriteSet writeSet = 
lh.distributionSchedule.getWriteSet(entryId);
 
@@ -293,7 +291,7 @@ class PendingAddOp extends SafeRunnable implements 
WriteCallback {
                 clientCtx.getClientStats().getAddOpUrCounter().inc();
                 if 
(!clientCtx.getConf().disableEnsembleChangeFeature.isAvailable()
                         && !clientCtx.getConf().delayEnsembleChange) {
-                    lh.getDelayedWriteFailedBookies().putIfAbsent(bookieIndex, 
addr);
+                    lh.notifyWriteFailed(bookieIndex, addr);
                 }
             }
             // even the add operation is completed, but because we don't reset 
completed flag back to false when
diff --git 
a/bookkeeper-server/src/main/java/org/apache/bookkeeper/client/ReadOnlyLedgerHandle.java
 
b/bookkeeper-server/src/main/java/org/apache/bookkeeper/client/ReadOnlyLedgerHandle.java
index e2c9a44..e4794de 100644
--- 
a/bookkeeper-server/src/main/java/org/apache/bookkeeper/client/ReadOnlyLedgerHandle.java
+++ 
b/bookkeeper-server/src/main/java/org/apache/bookkeeper/client/ReadOnlyLedgerHandle.java
@@ -20,18 +20,14 @@
  */
 package org.apache.bookkeeper.client;
 
-import static com.google.common.base.Preconditions.checkArgument;
 import static com.google.common.base.Preconditions.checkState;
 
 import com.google.common.annotations.VisibleForTesting;
 
 import java.security.GeneralSecurityException;
-import java.util.ArrayList;
-import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
 import java.util.NavigableMap;
-import java.util.Optional;
 import java.util.Set;
 import java.util.TreeMap;
 import java.util.concurrent.CompletableFuture;
@@ -209,64 +205,6 @@ class ReadOnlyLedgerHandle extends LedgerHandle implements 
LedgerMetadataListene
         }, ctx);
     }
 
-    List<BookieSocketAddress> replaceBookiesInEnsemble(LedgerMetadata metadata,
-                                                       
List<BookieSocketAddress> oldEnsemble,
-                                                       Map<Integer, 
BookieSocketAddress> failedBookies)
-            throws BKException.BKNotEnoughBookiesException {
-        List<BookieSocketAddress> newEnsemble = new ArrayList<>(oldEnsemble);
-
-        int ensembleSize = metadata.getEnsembleSize();
-        int writeQ = metadata.getWriteQuorumSize();
-        int ackQ = metadata.getAckQuorumSize();
-        Map<String, byte[]> customMetadata = metadata.getCustomMetadata();
-
-        Set<BookieSocketAddress> exclude = new 
HashSet<>(failedBookies.values());
-
-        int replaced = 0;
-        for (Map.Entry<Integer, BookieSocketAddress> entry : 
failedBookies.entrySet()) {
-            int idx = entry.getKey();
-            BookieSocketAddress addr = entry.getValue();
-            if (LOG.isDebugEnabled()) {
-                LOG.debug("[EnsembleChange-L{}] replacing bookie: {} index: 
{}", getId(), addr, idx);
-            }
-
-            if (!newEnsemble.get(idx).equals(addr)) {
-                if (LOG.isDebugEnabled()) {
-                    LOG.debug("[EnsembleChange-L{}] Not changing failed bookie 
{} at index {}, already changed to {}",
-                              getId(), addr, idx, newEnsemble.get(idx));
-                }
-                continue;
-            }
-            try {
-                BookieSocketAddress newBookie = 
clientCtx.getBookieWatcher().replaceBookie(
-                        ensembleSize, writeQ, ackQ, customMetadata, 
newEnsemble, idx, exclude);
-                newEnsemble.set(idx, newBookie);
-
-                replaced++;
-            } catch (BKException.BKNotEnoughBookiesException e) {
-                // if there is no bookie replaced, we throw not enough bookie 
exception
-                if (replaced <= 0) {
-                    throw e;
-                } else {
-                    break;
-                }
-            }
-        }
-        return newEnsemble;
-    }
-
-    private static Set<Integer> diffEnsemble(List<BookieSocketAddress> e1,
-                                             List<BookieSocketAddress> e2) {
-        checkArgument(e1.size() == e2.size(), "Ensembles must be of same 
size");
-        Set<Integer> diff = new HashSet<>();
-        for (int i = 0; i < e1.size(); i++) {
-            if (!e1.get(i).equals(e2.get(i))) {
-                diff.add(i);
-            }
-        }
-        return diff;
-    }
-
     /**
      * For a read only ledger handle, this method will only ever be called 
during recovery,
      * when we are reading forward from LAC and writing back those entries. As 
such,
@@ -276,21 +214,19 @@ class ReadOnlyLedgerHandle extends LedgerHandle 
implements LedgerMetadataListene
      */
     @Override
     void handleBookieFailure(final Map<Integer, BookieSocketAddress> 
failedBookies) {
-        blockAddCompletions.incrementAndGet();
-
         // handleBookieFailure should always run in the ordered executor 
thread for this
         // ledger, so this synchronized should be unnecessary, but putting it 
here now
         // just in case (can be removed when we validate threads)
         synchronized (metadataLock) {
+            String logContext = 
String.format("[RecoveryEnsembleChange(ledger:%d)]", ledgerId);
+
             long lac = getLastAddConfirmed();
             LedgerMetadata metadata = getLedgerMetadata();
             List<BookieSocketAddress> currentEnsemble = getCurrentEnsemble();
             try {
-                List<BookieSocketAddress> newEnsemble = 
replaceBookiesInEnsemble(metadata, currentEnsemble,
-                                                                               
  failedBookies);
-
-                Set<Integer> replaced = diffEnsemble(currentEnsemble, 
newEnsemble);
-                blockAddCompletions.decrementAndGet();
+                List<BookieSocketAddress> newEnsemble = 
EnsembleUtils.replaceBookiesInEnsemble(
+                        clientCtx.getBookieWatcher(), metadata, 
currentEnsemble, failedBookies, logContext);
+                Set<Integer> replaced = 
EnsembleUtils.diffEnsemble(currentEnsemble, newEnsemble);
                 if (!replaced.isEmpty()) {
                     newEnsemblesFromRecovery.put(lac + 1, newEnsemble);
                     unsetSuccessAndSendWriteRequest(newEnsemble, replaced);
@@ -378,16 +314,14 @@ class ReadOnlyLedgerHandle extends LedgerHandle 
implements LedgerMetadataListene
                 (metadata) -> metadata.isInRecovery(),
                 (metadata) -> {
                     LedgerMetadataBuilder builder = 
LedgerMetadataBuilder.from(metadata);
-                    Optional<Long> lastEnsembleKey = 
metadata.getLastEnsembleKey();
-                    checkState(lastEnsembleKey.isPresent(),
-                               "Metadata shouldn't have been created without 
at least one ensemble");
+                    Long lastEnsembleKey = metadata.getLastEnsembleKey();
                     synchronized (metadataLock) {
                         newEnsemblesFromRecovery.entrySet().forEach(
                                 (e) -> {
-                                    checkState(e.getKey() >= 
lastEnsembleKey.get(),
+                                    checkState(e.getKey() >= lastEnsembleKey,
                                                "Once a ledger is in recovery, 
noone can add ensembles without closing");
                                     // Occurs when a bookie need to be 
replaced at very start of recovery
-                                    if 
(lastEnsembleKey.get().equals(e.getKey())) {
+                                    if (lastEnsembleKey.equals(e.getKey())) {
                                         
builder.replaceEnsembleEntry(e.getKey(), e.getValue());
                                     } else {
                                         builder.newEnsembleEntry(e.getKey(), 
e.getValue());
diff --git 
a/bookkeeper-server/src/main/java/org/apache/bookkeeper/client/api/WriteHandle.java
 
b/bookkeeper-server/src/main/java/org/apache/bookkeeper/client/api/WriteHandle.java
index edad5f4..95a1765 100644
--- 
a/bookkeeper-server/src/main/java/org/apache/bookkeeper/client/api/WriteHandle.java
+++ 
b/bookkeeper-server/src/main/java/org/apache/bookkeeper/client/api/WriteHandle.java
@@ -141,6 +141,14 @@ public interface WriteHandle extends ReadHandle, 
ForceableHandle {
      * entry of the ledger is. Once the ledger has been closed, all reads from 
the
      * ledger will return the same set of entries.
      *
+     * <p>The close operation can error if it finds conflicting metadata when 
it
+     * tries to write to the metadata store. On close, the metadata state is 
set to
+     * closed and lastEntry and length of the ledger are fixed in the 
metadata. A
+     * conflict occurs if the metadata in the metadata store has a different 
value for
+     * the lastEntry or length. If another process has updated the metadata, 
setting it
+     * to closed, but have fixed the lastEntry and length to the same values 
as this
+     * process is trying to write, the operation completes successfully.
+     *
      * @return an handle to access the result of the operation
      */
     @Override
@@ -152,6 +160,14 @@ public interface WriteHandle extends ReadHandle, 
ForceableHandle {
      * <p>Closing a ledger will ensure that all clients agree on what the last
      * entry of the ledger is. Once the ledger has been closed, all reads from 
the
      * ledger will return the same set of entries.
+     *
+     * <p>The close operation can error if it finds conflicting metadata when 
it
+     * tries to write to the metadata store. On close, the metadata state is 
set to
+     * closed and lastEntry and length of the ledger are fixed in the 
metadata. A
+     * conflict occurs if the metadata in the metadata store has a different 
value for
+     * the lastEntry or length. If another process has updated the metadata, 
setting it
+     * to closed, but have fixed the lastEntry and length to the same values 
as this
+     * process is trying to write, the operation completes successfully.
      */
     @Override
     default void close() throws BKException, InterruptedException {
diff --git 
a/bookkeeper-server/src/test/java/org/apache/bookkeeper/client/BookKeeperTest.java
 
b/bookkeeper-server/src/test/java/org/apache/bookkeeper/client/BookKeeperTest.java
index 0471e50..7be404d 100644
--- 
a/bookkeeper-server/src/test/java/org/apache/bookkeeper/client/BookKeeperTest.java
+++ 
b/bookkeeper-server/src/test/java/org/apache/bookkeeper/client/BookKeeperTest.java
@@ -536,12 +536,9 @@ public class BookKeeperTest extends 
BookKeeperClusterTestCase {
                 }
             }
 
-            try {
-                writeLh.close();
-                fail("should not be able to close the first LedgerHandler as a 
recovery has been performed");
-            } catch (BKException.BKMetadataVersionException expected) {
-            }
-
+            // should still be able to close as long as recovery closed the 
ledger
+            // with the same last entryId and length as in the write handle.
+            writeLh.close();
         }
     }
 
diff --git 
a/bookkeeper-server/src/test/java/org/apache/bookkeeper/client/ClientUtil.java 
b/bookkeeper-server/src/test/java/org/apache/bookkeeper/client/ClientUtil.java
index bb3e553..5add60f 100644
--- 
a/bookkeeper-server/src/test/java/org/apache/bookkeeper/client/ClientUtil.java
+++ 
b/bookkeeper-server/src/test/java/org/apache/bookkeeper/client/ClientUtil.java
@@ -17,11 +17,15 @@
  */
 package org.apache.bookkeeper.client;
 
+import static java.nio.charset.StandardCharsets.UTF_8;
+
 import io.netty.buffer.ByteBuf;
 import io.netty.buffer.Unpooled;
 
 import java.security.GeneralSecurityException;
+import java.util.function.Function;
 
+import 
org.apache.bookkeeper.proto.BookkeeperInternalCallbacks.GenericCallbackFuture;
 import org.apache.bookkeeper.proto.DataFormats.LedgerMetadataFormat.DigestType;
 import org.apache.bookkeeper.proto.checksum.DigestManager;
 import org.apache.bookkeeper.util.ByteBufList;
@@ -30,6 +34,8 @@ import org.apache.bookkeeper.util.ByteBufList;
  * Client utilities.
  */
 public class ClientUtil {
+    public static final byte[] PASSWD = "foobar".getBytes(UTF_8);
+
     public static ByteBuf generatePacket(long ledgerId, long entryId, long 
lastAddConfirmed,
                                                long length, byte[] data) 
throws GeneralSecurityException {
         return generatePacket(ledgerId, entryId, lastAddConfirmed, length, 
data, 0, data.length);
@@ -49,4 +55,21 @@ public class ClientUtil {
         return !handle.getLedgerMetadata().isClosed();
     }
 
+    public static LedgerMetadata setupLedger(ClientContext clientCtx, long 
ledgerId,
+                                             LedgerMetadataBuilder builder) 
throws Exception {
+        LedgerMetadata md = builder.withPassword(PASSWD).build();
+        GenericCallbackFuture<LedgerMetadata> mdPromise = new 
GenericCallbackFuture<>();
+        clientCtx.getLedgerManager().createLedgerMetadata(ledgerId, md, 
mdPromise);
+        return mdPromise.get();
+    }
+
+    public static LedgerMetadata transformMetadata(ClientContext clientCtx, 
long ledgerId,
+                                                   Function<LedgerMetadata, 
LedgerMetadata> transform)
+            throws Exception {
+        GenericCallbackFuture<LedgerMetadata> readPromise = new 
GenericCallbackFuture<>();
+        GenericCallbackFuture<LedgerMetadata> writePromise = new 
GenericCallbackFuture<>();
+        clientCtx.getLedgerManager().readLedgerMetadata(ledgerId, readPromise);
+        clientCtx.getLedgerManager().writeLedgerMetadata(ledgerId, 
transform.apply(readPromise.get()), writePromise);
+        return writePromise.get();
+    }
 }
diff --git 
a/bookkeeper-server/src/test/java/org/apache/bookkeeper/client/DeferredSyncTest.java
 
b/bookkeeper-server/src/test/java/org/apache/bookkeeper/client/DeferredSyncTest.java
index 95dec9c..996c902 100644
--- 
a/bookkeeper-server/src/test/java/org/apache/bookkeeper/client/DeferredSyncTest.java
+++ 
b/bookkeeper-server/src/test/java/org/apache/bookkeeper/client/DeferredSyncTest.java
@@ -19,6 +19,7 @@ package org.apache.bookkeeper.client;
 
 import static org.apache.bookkeeper.common.concurrent.FutureUtils.result;
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertTrue;
 import static org.junit.Assert.fail;
 
@@ -213,7 +214,7 @@ public class DeferredSyncTest extends 
MockBookKeeperTestCase {
                 // expected
             }
             LedgerHandle lh = (LedgerHandle) wh;
-            assertTrue(lh.getDelayedWriteFailedBookies().isEmpty());
+            assertFalse(lh.hasDelayedWriteFailedBookies());
         }
     }
 
diff --git 
a/bookkeeper-server/src/test/java/org/apache/bookkeeper/client/HandleFailuresTest.java
 
b/bookkeeper-server/src/test/java/org/apache/bookkeeper/client/HandleFailuresTest.java
new file mode 100644
index 0000000..dbcd8ba
--- /dev/null
+++ 
b/bookkeeper-server/src/test/java/org/apache/bookkeeper/client/HandleFailuresTest.java
@@ -0,0 +1,444 @@
+/*
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ *
+ */
+package org.apache.bookkeeper.client;
+
+import static org.apache.bookkeeper.util.TestUtils.assertEventuallyTrue;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.ArgumentMatchers.anyLong;
+import static org.mockito.Mockito.times;
+import static org.mockito.Mockito.verify;
+
+import com.google.common.collect.Lists;
+
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.ExecutionException;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.TimeoutException;
+
+import org.apache.bookkeeper.client.api.WriteFlag;
+import org.apache.bookkeeper.common.concurrent.FutureUtils;
+import org.apache.bookkeeper.net.BookieSocketAddress;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * Ledger recovery tests using mocks rather than a real cluster.
+ */
+public class HandleFailuresTest {
+    private static final Logger log = 
LoggerFactory.getLogger(LedgerRecovery2Test.class);
+
+    private static final BookieSocketAddress b1 = new 
BookieSocketAddress("b1", 3181);
+    private static final BookieSocketAddress b2 = new 
BookieSocketAddress("b2", 3181);
+    private static final BookieSocketAddress b3 = new 
BookieSocketAddress("b3", 3181);
+    private static final BookieSocketAddress b4 = new 
BookieSocketAddress("b4", 3181);
+    private static final BookieSocketAddress b5 = new 
BookieSocketAddress("b5", 3181);
+
+    @Test
+    public void testChangeTriggeredOneTimeForOneFailure() throws Exception {
+        MockClientContext clientCtx = MockClientContext.create();
+        LedgerMetadata md = ClientUtil.setupLedger(clientCtx, 10L,
+                                                   
LedgerMetadataBuilder.create().newEnsembleEntry(
+                                                           0L, 
Lists.newArrayList(b1, b2, b3)));
+
+        clientCtx.getMockRegistrationClient().addBookies(b4).get();
+        clientCtx.getMockBookieClient().errorBookies(b1);
+
+        LedgerHandle lh = new LedgerHandle(clientCtx, 10L, md, 
BookKeeper.DigestType.CRC32C,
+                                           ClientUtil.PASSWD, WriteFlag.NONE);
+        lh.appendAsync("entry1".getBytes());
+        lh.appendAsync("entry2".getBytes());
+        lh.appendAsync("entry3".getBytes());
+        lh.appendAsync("entry4".getBytes());
+        lh.appendAsync("entry5".getBytes()).get();
+
+        verify(clientCtx.getLedgerManager(), 
times(1)).writeLedgerMetadata(anyLong(), any(), any());
+        Assert.assertEquals(lh.getLedgerMetadata().getEnsembles().size(), 1);
+        Assert.assertEquals(lh.getLedgerMetadata().getEnsembles().get(0L), 
Lists.newArrayList(b4, b2, b3));
+    }
+
+    @Test
+    public void testSecondFailureOccursWhileFirstBeingHandled() throws 
Exception {
+        MockClientContext clientCtx = MockClientContext.create();
+        LedgerMetadata md = ClientUtil.setupLedger(clientCtx, 10L,
+                                                   
LedgerMetadataBuilder.create()
+                                                   
.withEnsembleSize(3).withWriteQuorumSize(3).withAckQuorumSize(3)
+                                                   .newEnsembleEntry(0L, 
Lists.newArrayList(b1, b2, b3)));
+
+        clientCtx.getMockRegistrationClient().addBookies(b4, b5).get();
+        CompletableFuture<Void> b2blocker = new CompletableFuture<>();
+        clientCtx.getMockBookieClient().setPreWriteHook(
+                (bookie, ledgerId, entryId) -> {
+                    if (bookie.equals(b1)) {
+                        return FutureUtils.exception(new 
BKException.BKWriteException());
+                    } else if (bookie.equals(b2)) {
+                        return b2blocker;
+                    } else {
+                        return FutureUtils.value(null);
+                    }
+                });
+        CompletableFuture<Void> metadataNotifier = new CompletableFuture<>();
+        CompletableFuture<Void> metadataBlocker = new CompletableFuture<>();
+        clientCtx.getMockLedgerManager().setPreWriteHook(
+                (ledgerId, metadata) -> {
+                    metadataNotifier.complete(null);
+                    return metadataBlocker;
+                });
+
+        LedgerHandle lh = new LedgerHandle(clientCtx, 10L, md, 
BookKeeper.DigestType.CRC32C,
+                                           ClientUtil.PASSWD, WriteFlag.NONE);
+        lh.appendAsync("entry1".getBytes());
+        lh.appendAsync("entry2".getBytes());
+        lh.appendAsync("entry3".getBytes());
+        lh.appendAsync("entry4".getBytes());
+        CompletableFuture<?> future = lh.appendAsync("entry5".getBytes());
+
+        metadataNotifier.get(); // wait for first metadata write to occur
+        b2blocker.completeExceptionally(new BKException.BKWriteException()); 
// make b2 requests fail
+        metadataBlocker.complete(null);
+
+        future.get();
+        verify(clientCtx.getLedgerManager(), 
times(2)).writeLedgerMetadata(anyLong(), any(), any());
+        Assert.assertEquals(lh.getLedgerMetadata().getEnsembles().size(), 1);
+        
Assert.assertTrue(lh.getLedgerMetadata().getEnsembles().get(0L).contains(b3));
+        
Assert.assertTrue(lh.getLedgerMetadata().getEnsembles().get(0L).contains(b4));
+        
Assert.assertTrue(lh.getLedgerMetadata().getEnsembles().get(0L).contains(b5));
+    }
+
+    @Test
+    public void testHandlingFailuresOneBookieFailsImmediately() throws 
Exception {
+        MockClientContext clientCtx = MockClientContext.create();
+        LedgerMetadata md = ClientUtil.setupLedger(clientCtx, 10L,
+                                                   
LedgerMetadataBuilder.create()
+                                                   
.withEnsembleSize(3).withWriteQuorumSize(3).withAckQuorumSize(3)
+                                                   .newEnsembleEntry(0L, 
Lists.newArrayList(b1, b2, b3)));
+        clientCtx.getMockRegistrationClient().addBookies(b4).get();
+        clientCtx.getMockBookieClient().errorBookies(b1);
+
+        LedgerHandle lh = new LedgerHandle(clientCtx, 10L, md, 
BookKeeper.DigestType.CRC32C,
+                                           ClientUtil.PASSWD, WriteFlag.NONE);
+        lh.append("entry1".getBytes());
+        lh.close();
+
+        Assert.assertTrue(lh.getLedgerMetadata().isClosed());
+        Assert.assertEquals(lh.getLedgerMetadata().getEnsembles().size(), 1);
+        Assert.assertEquals(lh.getLedgerMetadata().getEnsembles().get(0L), 
Lists.newArrayList(b4, b2, b3));
+    }
+
+    @Test
+    public void testHandlingFailuresOneBookieFailsAfterOneEntry() throws 
Exception {
+        MockClientContext clientCtx = MockClientContext.create();
+        LedgerMetadata md = ClientUtil.setupLedger(clientCtx, 10L,
+                                                   
LedgerMetadataBuilder.create()
+                                                   
.withEnsembleSize(3).withWriteQuorumSize(3).withAckQuorumSize(3)
+                                                   .newEnsembleEntry(0L, 
Lists.newArrayList(b1, b2, b3)));
+        clientCtx.getMockRegistrationClient().addBookies(b4).get();
+
+        LedgerHandle lh = new LedgerHandle(clientCtx, 10L, md, 
BookKeeper.DigestType.CRC32C,
+                                           ClientUtil.PASSWD, WriteFlag.NONE);
+        lh.append("entry1".getBytes());
+        clientCtx.getMockBookieClient().errorBookies(b1);
+        lh.append("entry2".getBytes());
+        lh.close();
+
+        Assert.assertTrue(lh.getLedgerMetadata().isClosed());
+        Assert.assertEquals(lh.getLedgerMetadata().getEnsembles().size(), 2);
+        Assert.assertEquals(lh.getLedgerMetadata().getEnsembles().get(0L), 
Lists.newArrayList(b1, b2, b3));
+        Assert.assertEquals(lh.getLedgerMetadata().getEnsembles().get(1L), 
Lists.newArrayList(b4, b2, b3));
+        Assert.assertEquals(lh.getLedgerMetadata().getLastEntryId(), 1L);
+    }
+
+    @Test
+    public void 
testHandlingFailuresMultipleBookieFailImmediatelyNotEnoughToReplace() throws 
Exception {
+        MockClientContext clientCtx = MockClientContext.create();
+        LedgerMetadata md = ClientUtil.setupLedger(clientCtx, 10L,
+                                                   
LedgerMetadataBuilder.create()
+                                                   
.withEnsembleSize(3).withWriteQuorumSize(3).withAckQuorumSize(3)
+                                                   .newEnsembleEntry(0L, 
Lists.newArrayList(b1, b2, b3)));
+        clientCtx.getMockBookieClient().errorBookies(b1, b2);
+
+        LedgerHandle lh = new LedgerHandle(clientCtx, 10L, md, 
BookKeeper.DigestType.CRC32C,
+                                           ClientUtil.PASSWD, WriteFlag.NONE);
+        try {
+            lh.append("entry1".getBytes());
+            Assert.fail("Shouldn't have been able to add");
+        } catch (BKException.BKNotEnoughBookiesException bke) {
+            // correct behaviour
+            assertEventuallyTrue("Failure to add should trigger ledger 
closure",
+                                 () -> lh.getLedgerMetadata().isClosed());
+            Assert.assertEquals("Ledger should be empty",
+                                lh.getLedgerMetadata().getLastEntryId(), 
LedgerHandle.INVALID_ENTRY_ID);
+            Assert.assertEquals("Should be only one ensemble", 
lh.getLedgerMetadata().getEnsembles().size(), 1);
+            Assert.assertEquals("Ensemble shouldn't have changed", 
lh.getLedgerMetadata().getEnsembles().get(0L),
+                                Lists.newArrayList(b1, b2, b3));
+        }
+    }
+
+    @Test
+    public void 
testHandlingFailuresMultipleBookieFailAfterOneEntryNotEnoughToReplace() throws 
Exception {
+        MockClientContext clientCtx = MockClientContext.create();
+        LedgerMetadata md = ClientUtil.setupLedger(clientCtx, 10L,
+                                                   
LedgerMetadataBuilder.create()
+                                                   
.withEnsembleSize(3).withWriteQuorumSize(3).withAckQuorumSize(3)
+                                                   .newEnsembleEntry(0L, 
Lists.newArrayList(b1, b2, b3)));
+
+        LedgerHandle lh = new LedgerHandle(clientCtx, 10L, md, 
BookKeeper.DigestType.CRC32C,
+                                           ClientUtil.PASSWD, WriteFlag.NONE);
+        lh.append("entry1".getBytes());
+
+        clientCtx.getMockBookieClient().errorBookies(b1, b2);
+
+        try {
+            lh.append("entry2".getBytes());
+            Assert.fail("Shouldn't have been able to add");
+        } catch (BKException.BKNotEnoughBookiesException bke) {
+            // correct behaviour
+            assertEventuallyTrue("Failure to add should trigger ledger 
closure",
+                                 () -> lh.getLedgerMetadata().isClosed());
+            Assert.assertEquals("Ledger should be empty", 
lh.getLedgerMetadata().getLastEntryId(), 0L);
+            Assert.assertEquals("Should be only one ensemble", 
lh.getLedgerMetadata().getEnsembles().size(), 1);
+            Assert.assertEquals("Ensemble shouldn't have changed", 
lh.getLedgerMetadata().getEnsembles().get(0L),
+                                Lists.newArrayList(b1, b2, b3));
+        }
+    }
+
+    @Test
+    public void testClientClosesWhileFailureHandlerInProgress() throws 
Exception {
+        MockClientContext clientCtx = MockClientContext.create();
+        LedgerMetadata md = ClientUtil.setupLedger(clientCtx, 10L,
+                                                   
LedgerMetadataBuilder.create()
+                                                   
.withEnsembleSize(3).withWriteQuorumSize(3).withAckQuorumSize(3)
+                                                   .newEnsembleEntry(0L, 
Lists.newArrayList(b1, b2, b3)));
+        clientCtx.getMockRegistrationClient().addBookies(b4).get();
+        clientCtx.getMockBookieClient().errorBookies(b2);
+
+        CompletableFuture<Void> changeInProgress = new CompletableFuture<>();
+        CompletableFuture<Void> blockEnsembleChange = new 
CompletableFuture<>();
+        clientCtx.getMockLedgerManager().setPreWriteHook((ledgerId, metadata) 
-> {
+                if (metadata.getEnsembles().get(0L).get(1).equals(b4)) { // 
block the write trying to replace b2 with b4
+                    changeInProgress.complete(null);
+                    return blockEnsembleChange;
+                } else {
+                    return FutureUtils.value(null);
+                }
+            });
+
+        LedgerHandle lh = new LedgerHandle(clientCtx, 10L, md, 
BookKeeper.DigestType.CRC32C,
+                                           ClientUtil.PASSWD, WriteFlag.NONE);
+        CompletableFuture<?> future = lh.appendAsync("entry1".getBytes());
+        changeInProgress.get();
+
+        lh.close();
+
+        blockEnsembleChange.complete(null); // allow ensemble change to 
continue
+        try {
+            future.get();
+            Assert.fail("Add shouldn't have succeeded");
+        } catch (ExecutionException ee) {
+            Assert.assertEquals(ee.getCause().getClass(), 
BKException.BKLedgerClosedException.class);
+        }
+        Assert.assertTrue(lh.getLedgerMetadata().isClosed());
+        Assert.assertEquals(lh.getLedgerMetadata().getEnsembles().size(), 1);
+        Assert.assertEquals(lh.getLedgerMetadata().getEnsembles().get(0L), 
Lists.newArrayList(b1, b2, b3));
+        Assert.assertEquals(lh.getLedgerMetadata().getLastEntryId(), 
LedgerHandle.INVALID_ENTRY_ID);
+    }
+
+    @Test
+    public void testMetadataSetToClosedDuringFailureHandler() throws Exception 
{
+                MockClientContext clientCtx = MockClientContext.create();
+        LedgerMetadata md = ClientUtil.setupLedger(clientCtx, 10L,
+                                                   
LedgerMetadataBuilder.create()
+                                                   
.withEnsembleSize(3).withWriteQuorumSize(3).withAckQuorumSize(3)
+                                                   .newEnsembleEntry(0L, 
Lists.newArrayList(b1, b2, b3)));
+        clientCtx.getMockRegistrationClient().addBookies(b4).get();
+        clientCtx.getMockBookieClient().errorBookies(b2);
+
+        CompletableFuture<Void> changeInProgress = new CompletableFuture<>();
+        CompletableFuture<Void> blockEnsembleChange = new 
CompletableFuture<>();
+        clientCtx.getMockLedgerManager().setPreWriteHook((ledgerId, metadata) 
-> {
+                if (metadata.getEnsembles().get(0L).get(1).equals(b4)) { // 
block the write trying to replace b2 with b4
+                    changeInProgress.complete(null);
+                    return blockEnsembleChange;
+                } else {
+                    return FutureUtils.value(null);
+                }
+            });
+
+        LedgerHandle lh = new LedgerHandle(clientCtx, 10L, md, 
BookKeeper.DigestType.CRC32C,
+                                           ClientUtil.PASSWD, WriteFlag.NONE);
+        CompletableFuture<?> future = lh.appendAsync("entry1".getBytes());
+        changeInProgress.get();
+
+        ClientUtil.transformMetadata(clientCtx, 10L,
+                                     (metadata) -> 
LedgerMetadataBuilder.from(metadata).closingAt(1234L, 10L).build());
+
+        blockEnsembleChange.complete(null); // allow ensemble change to 
continue
+        try {
+            future.get();
+            Assert.fail("Add shouldn't have succeeded");
+        } catch (ExecutionException ee) {
+            Assert.assertEquals(ee.getCause().getClass(), 
BKException.BKLedgerClosedException.class);
+        }
+        Assert.assertTrue(lh.getLedgerMetadata().isClosed());
+        Assert.assertEquals(lh.getLedgerMetadata().getEnsembles().size(), 1);
+        Assert.assertEquals(lh.getLedgerMetadata().getEnsembles().get(0L), 
Lists.newArrayList(b1, b2, b3));
+        Assert.assertEquals(lh.getLedgerMetadata().getLastEntryId(), 1234L);
+    }
+
+    @Test
+    public void testMetadataSetToInRecoveryDuringFailureHandler() throws 
Exception {
+                MockClientContext clientCtx = MockClientContext.create();
+        LedgerMetadata md = ClientUtil.setupLedger(clientCtx, 10L,
+                                                   
LedgerMetadataBuilder.create()
+                                                   
.withEnsembleSize(3).withWriteQuorumSize(3).withAckQuorumSize(3)
+                                                   .newEnsembleEntry(0L, 
Lists.newArrayList(b1, b2, b3)));
+        clientCtx.getMockRegistrationClient().addBookies(b4).get();
+        clientCtx.getMockBookieClient().errorBookies(b2);
+
+        CompletableFuture<Void> changeInProgress = new CompletableFuture<>();
+        CompletableFuture<Void> blockEnsembleChange = new 
CompletableFuture<>();
+        clientCtx.getMockLedgerManager().setPreWriteHook((ledgerId, metadata) 
-> {
+                if (metadata.getEnsembles().get(0L).get(1).equals(b4)) { // 
block the write trying to replace b2 with b4
+                    changeInProgress.complete(null);
+                    return blockEnsembleChange;
+                } else {
+                    return FutureUtils.value(null);
+                }
+            });
+
+        LedgerHandle lh = new LedgerHandle(clientCtx, 10L, md, 
BookKeeper.DigestType.CRC32C,
+                                           ClientUtil.PASSWD, WriteFlag.NONE);
+        CompletableFuture<?> future = lh.appendAsync("entry1".getBytes());
+        changeInProgress.get();
+
+        ClientUtil.transformMetadata(clientCtx, 10L,
+                                     (metadata) -> 
LedgerMetadataBuilder.from(metadata).withInRecoveryState().build());
+
+        blockEnsembleChange.complete(null); // allow ensemble change to 
continue
+        try {
+            future.get();
+            Assert.fail("Add shouldn't have succeeded");
+        } catch (ExecutionException ee) {
+            Assert.assertEquals(ee.getCause().getClass(), 
BKException.BKLedgerFencedException.class);
+        }
+        Assert.assertFalse(lh.getLedgerMetadata().isClosed());
+        Assert.assertEquals(lh.getLedgerMetadata().getEnsembles().size(), 1);
+        Assert.assertEquals(lh.getLedgerMetadata().getEnsembles().get(0L), 
Lists.newArrayList(b1, b2, b3));
+    }
+
+    @Test
+    public void testOldEnsembleChangedDuringFailureHandler() throws Exception {
+        MockClientContext clientCtx = MockClientContext.create();
+        LedgerMetadata md = ClientUtil.setupLedger(clientCtx, 10L,
+                                                   
LedgerMetadataBuilder.create()
+                                                   
.withEnsembleSize(3).withWriteQuorumSize(3).withAckQuorumSize(3)
+                                                   .newEnsembleEntry(0L, 
Lists.newArrayList(b1, b2, b3)));
+
+        LedgerHandle lh = new LedgerHandle(clientCtx, 10L, md, 
BookKeeper.DigestType.CRC32C,
+                                           ClientUtil.PASSWD, WriteFlag.NONE);
+        lh.append("entry1".getBytes());
+        clientCtx.getMockRegistrationClient().addBookies(b4).get();
+        clientCtx.getMockBookieClient().errorBookies(b3);
+        lh.append("entry2".getBytes());
+
+        Assert.assertEquals(lh.getLedgerMetadata().getEnsembles().size(), 2);
+        Assert.assertEquals(lh.getLedgerMetadata().getEnsembles().get(0L), 
Lists.newArrayList(b1, b2, b3));
+        Assert.assertEquals(lh.getLedgerMetadata().getEnsembles().get(1L), 
Lists.newArrayList(b1, b2, b4));
+
+
+        CompletableFuture<Void> changeInProgress = new CompletableFuture<>();
+        CompletableFuture<Void> blockEnsembleChange = new 
CompletableFuture<>();
+        clientCtx.getMockLedgerManager().setPreWriteHook((ledgerId, metadata) 
-> {
+                 // block the write trying to replace b1 with b5
+                if (metadata.getEnsembles().size() > 2
+                    && metadata.getEnsembles().get(2L).get(0).equals(b5)) {
+                    changeInProgress.complete(null);
+                    return blockEnsembleChange;
+                } else {
+                    return FutureUtils.value(null);
+                }
+            });
+
+        clientCtx.getMockRegistrationClient().addBookies(b5).get();
+        clientCtx.getMockBookieClient().errorBookies(b1);
+
+        CompletableFuture<?> future = lh.appendAsync("entry3".getBytes());
+        changeInProgress.get();
+
+        ClientUtil.transformMetadata(clientCtx, 10L,
+                                     (metadata) -> 
LedgerMetadataBuilder.from(metadata).replaceEnsembleEntry(
+                                             0L, Lists.newArrayList(b4, b2, 
b5)).build());
+
+        blockEnsembleChange.complete(null); // allow ensemble change to 
continue
+        future.get();
+
+        Assert.assertFalse(lh.getLedgerMetadata().isClosed());
+        Assert.assertEquals(lh.getLedgerMetadata().getEnsembles().size(), 3);
+        Assert.assertEquals(lh.getLedgerMetadata().getEnsembles().get(0L), 
Lists.newArrayList(b4, b2, b5));
+        Assert.assertEquals(lh.getLedgerMetadata().getEnsembles().get(1L), 
Lists.newArrayList(b1, b2, b4));
+        Assert.assertEquals(lh.getLedgerMetadata().getEnsembles().get(2L), 
Lists.newArrayList(b5, b2, b4));
+    }
+
+    @Test
+    public void testNoAddsAreCompletedWhileFailureHandlingInProgress() throws 
Exception {
+        MockClientContext clientCtx = MockClientContext.create();
+        LedgerMetadata md = ClientUtil.setupLedger(clientCtx, 10L,
+                                                   
LedgerMetadataBuilder.create()
+                                                   
.withEnsembleSize(3).withWriteQuorumSize(3).withAckQuorumSize(2)
+                                                   .newEnsembleEntry(0L, 
Lists.newArrayList(b1, b2, b3)));
+
+        clientCtx.getMockRegistrationClient().addBookies(b4).get();
+        clientCtx.getMockBookieClient().errorBookies(b3);
+
+        LedgerHandle lh = new LedgerHandle(clientCtx, 10L, md, 
BookKeeper.DigestType.CRC32C,
+                                           ClientUtil.PASSWD, WriteFlag.NONE);
+        lh.append("entry1".getBytes());
+
+        CompletableFuture<Void> changeInProgress = new CompletableFuture<>();
+        CompletableFuture<Void> blockEnsembleChange = new 
CompletableFuture<>();
+        clientCtx.getMockLedgerManager().setPreWriteHook((ledgerId, metadata) 
-> {
+                 // block the write trying to replace b3 with b4
+                if (metadata.getEnsembles().get(1L).get(2).equals(b4)) {
+                    changeInProgress.complete(null);
+                    return blockEnsembleChange;
+                } else {
+                    return FutureUtils.value(null);
+                }
+            });
+
+        CompletableFuture<?> future = lh.appendAsync("entry2".getBytes());
+        changeInProgress.get();
+        try {
+            future.get(1, TimeUnit.SECONDS);
+            Assert.fail("Shouldn't complete");
+        } catch (TimeoutException te) {
+        }
+        blockEnsembleChange.complete(null);
+        future.get();
+
+        Assert.assertEquals(lh.getLedgerMetadata().getEnsembles().size(), 2);
+        Assert.assertEquals(lh.getLedgerMetadata().getEnsembles().get(0L), 
Lists.newArrayList(b1, b2, b3));
+        Assert.assertEquals(lh.getLedgerMetadata().getEnsembles().get(1L), 
Lists.newArrayList(b1, b2, b4));
+    }
+}
diff --git 
a/bookkeeper-server/src/test/java/org/apache/bookkeeper/client/LedgerClose2Test.java
 
b/bookkeeper-server/src/test/java/org/apache/bookkeeper/client/LedgerClose2Test.java
new file mode 100644
index 0000000..0194e48
--- /dev/null
+++ 
b/bookkeeper-server/src/test/java/org/apache/bookkeeper/client/LedgerClose2Test.java
@@ -0,0 +1,269 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.bookkeeper.client;
+
+import com.google.common.collect.Lists;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.ExecutionException;
+import org.apache.bookkeeper.client.api.WriteFlag;
+import org.apache.bookkeeper.common.concurrent.FutureUtils;
+import org.apache.bookkeeper.net.BookieSocketAddress;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * Ledger recovery tests using mocks rather than a real cluster.
+ */
+public class LedgerClose2Test {
+    private static final Logger log = 
LoggerFactory.getLogger(LedgerRecovery2Test.class);
+
+    private static final BookieSocketAddress b1 = new 
BookieSocketAddress("b1", 3181);
+    private static final BookieSocketAddress b2 = new 
BookieSocketAddress("b2", 3181);
+    private static final BookieSocketAddress b3 = new 
BookieSocketAddress("b3", 3181);
+    private static final BookieSocketAddress b4 = new 
BookieSocketAddress("b4", 3181);
+    private static final BookieSocketAddress b5 = new 
BookieSocketAddress("b5", 3181);
+
+    @Test
+    public void testTryAddAfterCloseHasBeenCalled() throws Exception {
+        MockClientContext clientCtx = MockClientContext.create();
+
+        for (int i = 0; i < 1000; i++) {
+            LedgerMetadata md = ClientUtil.setupLedger(clientCtx, i,
+                                                       
LedgerMetadataBuilder.create().newEnsembleEntry(
+                                                               0L, 
Lists.newArrayList(b1, b2, b3)));
+            LedgerHandle lh = new LedgerHandle(clientCtx, i, md, 
BookKeeper.DigestType.CRC32C,
+                                               ClientUtil.PASSWD, 
WriteFlag.NONE);
+            CompletableFuture<?> closeFuture = lh.closeAsync();
+            try {
+                long eid = lh.append("entry".getBytes());
+
+                // if it succeeds, it should be in final ledge
+                closeFuture.get();
+                Assert.assertTrue(lh.getLedgerMetadata().isClosed());
+                Assert.assertEquals(lh.getLedgerMetadata().getLastEntryId(), 
eid);
+            } catch (BKException.BKLedgerClosedException bke) {
+                closeFuture.get();
+                Assert.assertTrue(lh.getLedgerMetadata().isClosed());
+                Assert.assertEquals(lh.getLedgerMetadata().getLastEntryId(), 
LedgerHandle.INVALID_ENTRY_ID);
+            }
+        }
+    }
+
+    @Test
+    public void testMetadataChangedDuringClose() throws Exception {
+        MockClientContext clientCtx = MockClientContext.create();
+        LedgerMetadata md = ClientUtil.setupLedger(clientCtx, 10L,
+                                                   
LedgerMetadataBuilder.create()
+                                                   
.withEnsembleSize(3).withWriteQuorumSize(3).withAckQuorumSize(2)
+                                                   .newEnsembleEntry(0L, 
Lists.newArrayList(b1, b2, b3)));
+
+
+        LedgerHandle lh = new LedgerHandle(clientCtx, 10L, md, 
BookKeeper.DigestType.CRC32C,
+                                           ClientUtil.PASSWD, WriteFlag.NONE);
+        lh.append("entry1".getBytes());
+        clientCtx.getMockRegistrationClient().addBookies(b4).get();
+        clientCtx.getMockBookieClient().errorBookies(b3);
+        lh.append("entry2".getBytes());
+
+        CompletableFuture<Void> closeInProgress = new CompletableFuture<>();
+        CompletableFuture<Void> blockClose = new CompletableFuture<>();
+        clientCtx.getMockLedgerManager().setPreWriteHook((ledgerId, metadata) 
-> {
+                 // block the write trying to replace b3 with b4
+                if (metadata.isClosed()) {
+                    closeInProgress.complete(null);
+                    return blockClose;
+                } else {
+                    return FutureUtils.value(null);
+                }
+            });
+        CompletableFuture<?> closeFuture = lh.closeAsync();
+        closeInProgress.get();
+
+        ClientUtil.transformMetadata(clientCtx, 10L,
+                                     (metadata) -> 
LedgerMetadataBuilder.from(metadata).replaceEnsembleEntry(
+                                             0L, Lists.newArrayList(b4, b2, 
b5)).build());
+
+        blockClose.complete(null);
+        closeFuture.get();
+
+        Assert.assertTrue(lh.getLedgerMetadata().isClosed());
+        Assert.assertEquals(lh.getLedgerMetadata().getEnsembles().size(), 2);
+        Assert.assertEquals(lh.getLedgerMetadata().getEnsembles().get(0L), 
Lists.newArrayList(b4, b2, b5));
+        Assert.assertEquals(lh.getLedgerMetadata().getEnsembles().get(1L), 
Lists.newArrayList(b1, b2, b4));
+        Assert.assertEquals(lh.getLedgerMetadata().getLastEntryId(), 1L);
+    }
+
+    @Test
+    public void testMetadataCloseWithCorrectLengthDuringClose() throws 
Exception {
+        MockClientContext clientCtx = MockClientContext.create();
+        LedgerMetadata md = ClientUtil.setupLedger(clientCtx, 10L,
+                                                   
LedgerMetadataBuilder.create()
+                                                   
.withEnsembleSize(3).withWriteQuorumSize(3).withAckQuorumSize(2)
+                                                   .newEnsembleEntry(0L, 
Lists.newArrayList(b1, b2, b3)));
+
+
+        LedgerHandle lh = new LedgerHandle(clientCtx, 10L, md, 
BookKeeper.DigestType.CRC32C,
+                                           ClientUtil.PASSWD, WriteFlag.NONE);
+        long lac = lh.append("entry1".getBytes());
+        long length = lh.getLength();
+
+        CompletableFuture<Void> closeInProgress = new CompletableFuture<>();
+        CompletableFuture<Void> blockClose = new CompletableFuture<>();
+        clientCtx.getMockLedgerManager().setPreWriteHook((ledgerId, metadata) 
-> {
+                // block the write trying to do the first close
+                if (!closeInProgress.isDone() && metadata.isClosed()) {
+                    closeInProgress.complete(null);
+                    return blockClose;
+                } else {
+                    return FutureUtils.value(null);
+                }
+            });
+        CompletableFuture<?> closeFuture = lh.closeAsync();
+        closeInProgress.get();
+
+        ClientUtil.transformMetadata(clientCtx, 10L,
+                (metadata) -> 
LedgerMetadataBuilder.from(metadata).closingAt(lac, length).build());
+
+        blockClose.complete(null);
+        closeFuture.get();
+
+        Assert.assertTrue(lh.getLedgerMetadata().isClosed());
+        Assert.assertEquals(lh.getLedgerMetadata().getEnsembles().size(), 1);
+        Assert.assertEquals(lh.getLedgerMetadata().getEnsembles().get(0L), 
Lists.newArrayList(b1, b2, b3));
+        Assert.assertEquals(lh.getLedgerMetadata().getLastEntryId(), lac);
+        Assert.assertEquals(lh.getLedgerMetadata().getLength(), length);
+    }
+
+    @Test
+    public void testMetadataCloseWithDifferentLengthDuringClose() throws 
Exception {
+        MockClientContext clientCtx = MockClientContext.create();
+        LedgerMetadata md = ClientUtil.setupLedger(clientCtx, 10L,
+                                                   
LedgerMetadataBuilder.create()
+                                                   
.withEnsembleSize(3).withWriteQuorumSize(3).withAckQuorumSize(2)
+                                                   .newEnsembleEntry(0L, 
Lists.newArrayList(b1, b2, b3)));
+
+
+        LedgerHandle lh = new LedgerHandle(clientCtx, 10L, md, 
BookKeeper.DigestType.CRC32C,
+                                           ClientUtil.PASSWD, WriteFlag.NONE);
+        long lac = lh.append("entry1".getBytes());
+        long length = lh.getLength();
+
+        CompletableFuture<Void> closeInProgress = new CompletableFuture<>();
+        CompletableFuture<Void> blockClose = new CompletableFuture<>();
+        clientCtx.getMockLedgerManager().setPreWriteHook((ledgerId, metadata) 
-> {
+                // block the write trying to do the first close
+                if (!closeInProgress.isDone() && metadata.isClosed()) {
+                    closeInProgress.complete(null);
+                    return blockClose;
+                } else {
+                    return FutureUtils.value(null);
+                }
+            });
+        CompletableFuture<?> closeFuture = lh.closeAsync();
+        closeInProgress.get();
+
+        /* close with different length. can happen in cases where there's a 
write outstanding */
+        ClientUtil.transformMetadata(clientCtx, 10L,
+                (metadata) -> 
LedgerMetadataBuilder.from(metadata).closingAt(lac + 1, length + 100).build());
+
+        blockClose.complete(null);
+        try {
+            closeFuture.get();
+            Assert.fail("Close should fail. Ledger has been closed in a state 
we don't know how to untangle");
+        } catch (ExecutionException ee) {
+            Assert.assertEquals(ee.getCause().getClass(), 
BKException.BKMetadataVersionException.class);
+        }
+    }
+
+    @Test
+    public void testMetadataCloseMarkedInRecoveryWhileClosing() throws 
Exception {
+        MockClientContext clientCtx = MockClientContext.create();
+        LedgerMetadata md = ClientUtil.setupLedger(clientCtx, 10L,
+                                                   
LedgerMetadataBuilder.create()
+                                                   
.withEnsembleSize(3).withWriteQuorumSize(3).withAckQuorumSize(2)
+                                                   .newEnsembleEntry(0L, 
Lists.newArrayList(b1, b2, b3)));
+
+        LedgerHandle lh = new LedgerHandle(clientCtx, 10L, md, 
BookKeeper.DigestType.CRC32C,
+                                           ClientUtil.PASSWD, WriteFlag.NONE);
+        long lac = lh.append("entry1".getBytes());
+        long length = lh.getLength();
+
+        CompletableFuture<Void> closeInProgress = new CompletableFuture<>();
+        CompletableFuture<Void> blockClose = new CompletableFuture<>();
+        clientCtx.getMockLedgerManager().setPreWriteHook((ledgerId, metadata) 
-> {
+                // block the write trying to do the first close
+                if (metadata.isClosed()) {
+                    closeInProgress.complete(null);
+                    return blockClose;
+                } else {
+                    return FutureUtils.value(null);
+                }
+            });
+        CompletableFuture<?> closeFuture = lh.closeAsync();
+        closeInProgress.get();
+
+        ClientUtil.transformMetadata(clientCtx, 10L,
+                (metadata) -> 
LedgerMetadataBuilder.from(metadata).withInRecoveryState().build());
+
+        blockClose.complete(null);
+
+        closeFuture.get(); // should override in recovery, since this handle 
knows what it has written
+        Assert.assertTrue(lh.getLedgerMetadata().isClosed());
+        Assert.assertEquals(lh.getLedgerMetadata().getEnsembles().size(), 1);
+        Assert.assertEquals(lh.getLedgerMetadata().getEnsembles().get(0L), 
Lists.newArrayList(b1, b2, b3));
+        Assert.assertEquals(lh.getLedgerMetadata().getLastEntryId(), lac);
+        Assert.assertEquals(lh.getLedgerMetadata().getLength(), length);
+    }
+
+    @Test
+    public void testCloseWhileAddInProgress() throws Exception {
+        MockClientContext clientCtx = MockClientContext.create();
+        LedgerMetadata md = ClientUtil.setupLedger(clientCtx, 10L,
+                                                   
LedgerMetadataBuilder.create()
+                                                   
.withEnsembleSize(3).withWriteQuorumSize(3).withAckQuorumSize(2)
+                                                   .newEnsembleEntry(0L, 
Lists.newArrayList(b1, b2, b3)));
+        // block all entry writes from completing
+        CompletableFuture<Void> writesHittingBookies = new 
CompletableFuture<>();
+        clientCtx.getMockBookieClient().setPreWriteHook((bookie, ledgerId, 
entryId) -> {
+                writesHittingBookies.complete(null);
+                return new CompletableFuture<Void>();
+            });
+        LedgerHandle lh = new LedgerHandle(clientCtx, 10L, md, 
BookKeeper.DigestType.CRC32C,
+                                           ClientUtil.PASSWD, WriteFlag.NONE);
+        CompletableFuture<?> future = lh.appendAsync("entry1".getBytes());
+        writesHittingBookies.get();
+
+        lh.close();
+        try {
+            future.get();
+            Assert.fail("That write shouldn't have succeeded");
+        } catch (ExecutionException ee) {
+            Assert.assertEquals(ee.getCause().getClass(), 
BKException.BKLedgerClosedException.class);
+        }
+        Assert.assertTrue(lh.getLedgerMetadata().isClosed());
+        Assert.assertEquals(lh.getLedgerMetadata().getEnsembles().size(), 1);
+        Assert.assertEquals(lh.getLedgerMetadata().getEnsembles().get(0L), 
Lists.newArrayList(b1, b2, b3));
+        Assert.assertEquals(lh.getLedgerMetadata().getLastEntryId(), 
LedgerHandle.INVALID_ENTRY_ID);
+        Assert.assertEquals(lh.getLedgerMetadata().getLength(), 0);
+    }
+}
+
diff --git 
a/bookkeeper-server/src/test/java/org/apache/bookkeeper/client/MdcContextTest.java
 
b/bookkeeper-server/src/test/java/org/apache/bookkeeper/client/MdcContextTest.java
index 535b97a..89b0088 100644
--- 
a/bookkeeper-server/src/test/java/org/apache/bookkeeper/client/MdcContextTest.java
+++ 
b/bookkeeper-server/src/test/java/org/apache/bookkeeper/client/MdcContextTest.java
@@ -172,7 +172,9 @@ public class MdcContextTest extends 
BookKeeperClusterTestCase {
         lh.addEntry(1, entry);
         assertLogWithMdc("ledger_add_entry", "Could not connect to bookie");
         assertLogWithMdc("ledger_add_entry", "Failed to write entry");
-        assertLogWithMdc("ledger_add_entry", "New Ensemble");
+        //commented out until we figure out a way to preserve MDC through a 
call out
+        //to another thread pool
+        //assertLogWithMdc("ledger_add_entry", "New Ensemble");
     }
 
     @Test
@@ -197,7 +199,7 @@ public class MdcContextTest extends 
BookKeeperClusterTestCase {
         assertLogWithMdc("ledger_add_entry", "Error writing entry:0 to 
ledger:0");
         assertLogWithMdc("ledger_add_entry", "Add for failed on bookie");
         assertLogWithMdc("ledger_add_entry", "Failed to find 1 bookies");
-        assertLogWithMdc("ledger_add_entry", "Could not get additional bookie 
to remake ensemble, closing ledger: 0");
+        assertLogWithMdc("ledger_add_entry", "Closing ledger 0 due to 
NotEnoughBookiesException");
     }
 
     @Test
diff --git 
a/bookkeeper-server/src/test/java/org/apache/bookkeeper/client/TestDisableEnsembleChange.java
 
b/bookkeeper-server/src/test/java/org/apache/bookkeeper/client/TestDisableEnsembleChange.java
index f114cbf..4a4599f 100644
--- 
a/bookkeeper-server/src/test/java/org/apache/bookkeeper/client/TestDisableEnsembleChange.java
+++ 
b/bookkeeper-server/src/test/java/org/apache/bookkeeper/client/TestDisableEnsembleChange.java
@@ -22,6 +22,7 @@ package org.apache.bookkeeper.client;
 
 import static com.google.common.base.Charsets.UTF_8;
 import static 
org.apache.bookkeeper.util.BookKeeperConstants.FEATURE_DISABLE_ENSEMBLE_CHANGE;
+import static org.apache.bookkeeper.util.TestUtils.assertEventuallyTrue;
 import static org.junit.Assert.assertArrayEquals;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
@@ -164,8 +165,9 @@ public class TestDisableEnsembleChange extends 
BookKeeperClusterTestCase {
         } else {
             assertTrue("Should fail adding entries when enable ensemble change 
again.",
                     failTest.get());
-            assertTrue("Ledger should be closed when enable ensemble change 
again.",
-                    lh.getLedgerMetadata().isClosed());
+            // The ledger close occurs in the background, so assert that it 
happens eventually
+            assertEventuallyTrue("Ledger should be closed when enable ensemble 
change again.",
+                                 () -> lh.getLedgerMetadata().isClosed());
         }
     }
 
diff --git 
a/bookkeeper-server/src/test/java/org/apache/bookkeeper/client/TestReadLastConfirmedLongPoll.java
 
b/bookkeeper-server/src/test/java/org/apache/bookkeeper/client/TestReadLastConfirmedLongPoll.java
index d05f864..48f638c 100644
--- 
a/bookkeeper-server/src/test/java/org/apache/bookkeeper/client/TestReadLastConfirmedLongPoll.java
+++ 
b/bookkeeper-server/src/test/java/org/apache/bookkeeper/client/TestReadLastConfirmedLongPoll.java
@@ -38,11 +38,14 @@ import org.junit.runner.RunWith;
 import org.junit.runners.Parameterized;
 import org.junit.runners.Parameterized.Parameters;
 
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 /**
  * Test read last confirmed long by polling.
  */
 @RunWith(Parameterized.class)
 public class TestReadLastConfirmedLongPoll extends BookKeeperClusterTestCase {
+    private static final Logger log = 
LoggerFactory.getLogger(TestReadLastConfirmedLongPoll.class);
     final DigestType digestType;
 
     public TestReadLastConfirmedLongPoll(Class<? extends LedgerStorage> 
storageClass) {
@@ -153,7 +156,7 @@ public class TestReadLastConfirmedLongPoll extends 
BookKeeperClusterTestCase {
             ServerConfiguration[] confs = new ServerConfiguration[numEntries - 
1];
             for (int j = 0; j < numEntries - 1; j++) {
                 int idx = (i + 1 + j) % numEntries;
-                confs[j] = killBookie(lh.getCurrentEnsemble().get(idx));
+                confs[j] = 
killBookie(lh.getLedgerMetadata().getLastEnsembleValue().get(idx));
             }
 
             final AtomicBoolean entryAsExpected = new AtomicBoolean(false);
diff --git 
a/bookkeeper-server/src/test/java/org/apache/bookkeeper/meta/MockLedgerManager.java
 
b/bookkeeper-server/src/test/java/org/apache/bookkeeper/meta/MockLedgerManager.java
index 4586e09..ea04192 100644
--- 
a/bookkeeper-server/src/test/java/org/apache/bookkeeper/meta/MockLedgerManager.java
+++ 
b/bookkeeper-server/src/test/java/org/apache/bookkeeper/meta/MockLedgerManager.java
@@ -21,18 +21,16 @@ package org.apache.bookkeeper.meta;
 
 import com.google.common.base.Optional;
 
-import java.util.ArrayList;
 import java.util.HashMap;
-import java.util.List;
 import java.util.Map;
 
+import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;
-import java.util.function.Consumer;
 
 import org.apache.bookkeeper.client.BKException;
 import org.apache.bookkeeper.client.LedgerMetadata;
-
+import org.apache.bookkeeper.common.concurrent.FutureUtils;
 import org.apache.bookkeeper.proto.BookkeeperInternalCallbacks.GenericCallback;
 import 
org.apache.bookkeeper.proto.BookkeeperInternalCallbacks.LedgerMetadataListener;
 import org.apache.bookkeeper.proto.BookkeeperInternalCallbacks.Processor;
@@ -51,12 +49,17 @@ import org.slf4j.LoggerFactory;
 public class MockLedgerManager implements LedgerManager {
     static final Logger LOG = LoggerFactory.getLogger(MockLedgerManager.class);
 
-    boolean stallingWrites = false;
-    final List<Consumer<Integer>> stalledWrites = new ArrayList<>();
+    /**
+     * Hook for injecting errors or delays.
+     */
+    public interface Hook {
+        CompletableFuture<Void> runHook(long ledgerId, LedgerMetadata 
metadata);
+    }
 
     final Map<Long, Pair<LongVersion, byte[]>> metadataMap;
     final ExecutorService executor;
     final boolean ownsExecutor;
+    private Hook preWriteHook = (ledgerId, metadata) -> 
FutureUtils.value(null);
 
     public MockLedgerManager() {
         this(new HashMap<>(),
@@ -83,23 +86,8 @@ public class MockLedgerManager implements LedgerManager {
         }
     }
 
-    public void stallWrites() throws Exception {
-        synchronized (this) {
-            stallingWrites = true;
-        }
-    }
-
-    public void releaseStalledWrites(int rc) {
-        List<Consumer<Integer>> toRelease;
-        synchronized (this) {
-            stallingWrites = false;
-            toRelease = new ArrayList<>(stalledWrites);
-            stalledWrites.clear();
-        }
-
-        executor.execute(() -> {
-                toRelease.forEach(w -> w.accept(rc));
-            });
+    public void setPreWriteHook(Hook hook) {
+        this.preWriteHook = hook;
     }
 
     public void executeCallback(Runnable r) {
@@ -147,42 +135,35 @@ public class MockLedgerManager implements LedgerManager {
 
     @Override
     public void writeLedgerMetadata(long ledgerId, LedgerMetadata metadata, 
GenericCallback<LedgerMetadata> cb) {
-        Runnable write = () -> {
-            try {
-                LedgerMetadata oldMetadata = readMetadata(ledgerId);
-                if (oldMetadata == null) {
-                    executeCallback(() -> 
cb.operationComplete(BKException.Code.NoSuchLedgerExistsException, null));
-                } else if 
(!oldMetadata.getVersion().equals(metadata.getVersion())) {
-                    executeCallback(() -> 
cb.operationComplete(BKException.Code.MetadataVersionException, null));
-                } else {
-                    LongVersion oldVersion = (LongVersion) 
oldMetadata.getVersion();
-                    metadataMap.put(ledgerId, Pair.of(new 
LongVersion(oldVersion.getLongVersion() + 1),
-                                                      metadata.serialize()));
-                    LedgerMetadata readBack = readMetadata(ledgerId);
-                    executeCallback(() -> 
cb.operationComplete(BKException.Code.OK, readBack));
-                }
-            } catch (Exception e) {
-                LOG.error("Error writing metadata", e);
-                executeCallback(() -> 
cb.operationComplete(BKException.Code.MetaStoreException, null));
-            }
-        };
-
-        synchronized (this) {
-            if (stallingWrites) {
-                LOG.info("[L{}, stallId={}] Stalling write of metadata", 
ledgerId, System.identityHashCode(write));
-                stalledWrites.add((rc) -> {
-                        LOG.info("[L{}, stallid={}] Unstalled write", 
ledgerId, System.identityHashCode(write));
-
-                        if (rc == BKException.Code.OK) {
-                            write.run();
+        preWriteHook.runHook(ledgerId, metadata)
+            .thenComposeAsync((ignore) -> {
+                    try {
+                        LedgerMetadata oldMetadata = readMetadata(ledgerId);
+                        if (oldMetadata == null) {
+                            return FutureUtils.exception(new 
BKException.BKNoSuchLedgerExistsException());
+                        } else if 
(!oldMetadata.getVersion().equals(metadata.getVersion())) {
+                            return FutureUtils.exception(new 
BKException.BKMetadataVersionException());
                         } else {
-                            executeCallback(() -> cb.operationComplete(rc, 
null));
+                            LongVersion oldVersion = (LongVersion) 
oldMetadata.getVersion();
+                            metadataMap.put(ledgerId, Pair.of(new 
LongVersion(oldVersion.getLongVersion() + 1),
+                                                              
metadata.serialize()));
+                            LedgerMetadata readBack = readMetadata(ledgerId);
+                            return FutureUtils.value(readBack);
                         }
-                    });
-            } else {
-                executor.execute(write);
-            }
-        }
+                    } catch (Exception e) {
+                        LOG.error("Error writing metadata", e);
+                        return FutureUtils.exception(e);
+                    }
+                }, executor)
+            .whenComplete((res, ex) -> {
+                    if (ex != null) {
+                        executeCallback(() -> cb.operationComplete(
+                                                
BKException.getExceptionCode(ex, BKException.Code.MetaStoreException),
+                                                null));
+                    } else {
+                        executeCallback(() -> 
cb.operationComplete(BKException.Code.OK, res));
+                    }
+                });
     }
 
     @Override
diff --git 
a/bookkeeper-server/src/test/java/org/apache/bookkeeper/test/ConditionalSetTest.java
 
b/bookkeeper-server/src/test/java/org/apache/bookkeeper/test/ConditionalSetTest.java
index b6d1153..285d39d 100644
--- 
a/bookkeeper-server/src/test/java/org/apache/bookkeeper/test/ConditionalSetTest.java
+++ 
b/bookkeeper-server/src/test/java/org/apache/bookkeeper/test/ConditionalSetTest.java
@@ -20,8 +20,6 @@
  */
 package org.apache.bookkeeper.test;
 
-import static org.junit.Assert.fail;
-
 import java.io.IOException;
 
 import org.apache.bookkeeper.client.BKException;
@@ -92,15 +90,9 @@ public class ConditionalSetTest extends 
BookKeeperClusterTestCase {
         LOG.debug("Opened the ledger already");
 
         /*
-         * Writer tries to close the ledger, and if should fail.
+         * Writer tries to close the ledger, and it should succeed as recovery 
closed
+         * the ledger already, but with the correct LAC and length
          */
-        try {
-            lhWrite.close();
-            fail("Should have received an exception when trying to close the 
ledger.");
-        } catch (BKException e) {
-            /*
-             * Correctly failed to close the ledger
-             */
-        }
+        lhWrite.close();
     }
 }
diff --git 
a/bookkeeper-server/src/test/java/org/apache/bookkeeper/util/TestUtils.java 
b/bookkeeper-server/src/test/java/org/apache/bookkeeper/util/TestUtils.java
index 26b2448..3525607 100644
--- a/bookkeeper-server/src/test/java/org/apache/bookkeeper/util/TestUtils.java
+++ b/bookkeeper-server/src/test/java/org/apache/bookkeeper/util/TestUtils.java
@@ -24,13 +24,16 @@ package org.apache.bookkeeper.util;
 import java.io.File;
 import java.util.HashSet;
 import java.util.Set;
-
 import java.util.concurrent.TimeUnit;
+import java.util.function.BooleanSupplier;
+
 import lombok.extern.slf4j.Slf4j;
 import org.apache.bookkeeper.bookie.Bookie;
 import org.apache.bookkeeper.client.LedgerHandle;
 import org.apache.bookkeeper.client.api.ReadHandle;
 
+import org.junit.Assert;
+
 /**
  * Test utilities.
  */
@@ -77,4 +80,16 @@ public final class TestUtils {
         return lac;
     }
 
+    public static void assertEventuallyTrue(String description, 
BooleanSupplier predicate) throws Exception {
+        assertEventuallyTrue(description, predicate, 10, TimeUnit.SECONDS);
+    }
+
+    public static void assertEventuallyTrue(String description, 
BooleanSupplier predicate,
+                                            long duration, TimeUnit unit) 
throws Exception {
+        long iterations = unit.toMillis(duration) / 100;
+        for (int i = 0; i < iterations && !predicate.getAsBoolean(); i++) {
+            Thread.sleep(100);
+        }
+        Assert.assertTrue(description, predicate.getAsBoolean());
+    }
 }

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