sijie commented on a change in pull request #4403: File system offload
URL: https://github.com/apache/pulsar/pull/4403#discussion_r293301102
 
 

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 File path: 
tiered-storage/file-system/src/main/java/org/apache/bookkeeper/mledger/offload/filesystem/impl/FileSystemManagedLedgerOffloader.java
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+/**
+ * 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.mledger.offload.filesystem.impl;
+
+import com.google.common.annotations.VisibleForTesting;
+import com.google.common.collect.ImmutableMap;
+import com.google.protobuf.ByteString;
+import org.apache.bookkeeper.client.BookKeeper;
+import org.apache.bookkeeper.client.api.LedgerEntries;
+import org.apache.bookkeeper.client.api.LedgerEntry;
+import org.apache.bookkeeper.client.api.LedgerMetadata;
+import org.apache.bookkeeper.client.api.ReadHandle;
+import org.apache.bookkeeper.common.util.OrderedScheduler;
+import org.apache.bookkeeper.mledger.LedgerOffloader;
+import 
org.apache.bookkeeper.mledger.offload.filesystem.FileSystemLedgerOffloaderFactory;
+import 
org.apache.bookkeeper.mledger.offload.filesystem.TieredStorageConfigurationData;
+import org.apache.bookkeeper.net.BookieSocketAddress;
+import org.apache.bookkeeper.proto.DataFormats;
+import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.fs.FileSystem;
+import org.apache.hadoop.fs.Path;
+import org.apache.hadoop.io.BytesWritable;
+import org.apache.hadoop.io.IOUtils;
+import org.apache.hadoop.io.LongWritable;
+import org.apache.hadoop.io.MapFile;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.IOException;
+import java.util.Arrays;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Map;
+import java.util.UUID;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.ExecutionException;
+import java.util.stream.Collectors;
+import java.util.zip.Checksum;
+
+
+public class FileSystemManagedLedgerOffloader implements LedgerOffloader {
+
+    private static final Logger log = 
LoggerFactory.getLogger(FileSystemManagedLedgerOffloader.class);
+    private static final String STORAGE_BASE_PATH = "storageBasePath";
+    private static final String[] DRIVER_NAMES = {"filesystem"};
+    private final Configuration configuration;
+    private final String driverName;
+    private final String storageBasePath;
+    private final FileSystem fileSystem;
+    private OrderedScheduler scheduler;
+    private static final long ENTRIES_PER_READ = 100;
+    public static boolean driverSupported(String driver) {
+        return Arrays.stream(DRIVER_NAMES).anyMatch(d -> 
d.equalsIgnoreCase(driver));
+    }
+    @Override
+    public String getOffloadDriverName() {
+        return driverName;
+    }
+
+    public static FileSystemManagedLedgerOffloader 
create(TieredStorageConfigurationData conf, OrderedScheduler scheduler) throws 
IOException {
+        return new FileSystemManagedLedgerOffloader(conf, scheduler);
+    }
+
+    private FileSystemManagedLedgerOffloader(TieredStorageConfigurationData 
conf, OrderedScheduler scheduler) throws IOException {
+        this.configuration = new Configuration();
+        if (conf.getFileSystemProfilePath() != null) {
+            String[] paths = conf.getFileSystemProfilePath().split(",");
+            for (int i =0 ; i < paths.length; i++) {
+                configuration.addResource(new Path(paths[i]));
+            }
+        }
+        if (configuration.get("fs.hdfs.impl") == null) {
+            this.configuration.set("fs.hdfs.impl", 
"org.apache.hadoop.hdfs.DistributedFileSystem");
+        }
+        
this.configuration.setClassLoader(FileSystemLedgerOffloaderFactory.class.getClassLoader());
+        this.driverName = conf.getManagedLedgerOffloadDriver();
+        this.storageBasePath = configuration.get("hadoop.tmp.dir");
+        this.scheduler = scheduler;
+        this.fileSystem = FileSystem.get(configuration);
+    }
+    @VisibleForTesting
+    public FileSystemManagedLedgerOffloader(TieredStorageConfigurationData 
conf, OrderedScheduler scheduler, String testHDFSPath, String baseDir) throws 
IOException {
+        this.configuration = new Configuration();
+        this.configuration.set("fs.hdfs.impl", 
"org.apache.hadoop.hdfs.DistributedFileSystem");
+        this.configuration.set("fs.defaultFS", testHDFSPath);
+        
this.configuration.setClassLoader(FileSystemLedgerOffloaderFactory.class.getClassLoader());
+        this.driverName = conf.getManagedLedgerOffloadDriver();
+        this.configuration.set("hadoop.tmp.dir", baseDir);
+        this.storageBasePath = baseDir;
+        this.scheduler = scheduler;
+        this.fileSystem = FileSystem.get(configuration);
+
+    }
+
+    @Override
+    public Map<String, String> getOffloadDriverMetadata() {
+        return ImmutableMap.of(
+                STORAGE_BASE_PATH, storageBasePath
+        );
+    }
+
+    @Override
+    public CompletableFuture<Void> offload(ReadHandle readHandle, UUID uid, 
Map<String, String> extraMetadata) {
+        CompletableFuture<Void> promise = new CompletableFuture<>();
+        scheduler.chooseThread(readHandle.getId()).submit(() -> {
+            if (readHandle.getLength() == 0 || !readHandle.isClosed() || 
readHandle.getLastAddConfirmed() < 0) {
+                promise.completeExceptionally(
+                        new IllegalArgumentException("An empty or open ledger 
should never be offloaded"));
+                return;
+            }
+            long ledgerId = readHandle.getId();
+            String storagePath = getStoragePath(storageBasePath, 
extraMetadata.get("ManagedLedgerName"));
+            String dataFilePath = getDataFilePath(storagePath, ledgerId, uid);
+            LongWritable key = new LongWritable();
+            BytesWritable value = new BytesWritable();
+            try {
+                MapFile.Writer dataWriter = new MapFile.Writer(configuration,
+                        new Path(dataFilePath),
+                        MapFile.Writer.keyClass(LongWritable.class),
+                        MapFile.Writer.valueClass(BytesWritable.class));
+                key.set(-1);
+                byte[] ledgerMetadata = 
buildLedgerMetadataFormat(readHandle.getLedgerMetadata());
+                
value.set(buildLedgerMetadataFormat(readHandle.getLedgerMetadata()), 0, 
ledgerMetadata.length);
+                dataWriter.append(key, value);
+                long haveOffloadEntryNumber = 0;
+                do {
+                    long end = Math.min(haveOffloadEntryNumber + 
ENTRIES_PER_READ - 1, readHandle.getLastAddConfirmed());
+                    LedgerEntries ledgerEntriesOnce = 
readHandle.readAsync(haveOffloadEntryNumber, end).get();
+                    log.debug("read ledger entries. start: {}, end: {}", 
haveOffloadEntryNumber, end);
+                    Iterator<LedgerEntry> iterator = 
ledgerEntriesOnce.iterator();
+                    while (iterator.hasNext()) {
+                        LedgerEntry entry = iterator.next();
+                        long entryId = entry.getEntryId();
+                        key.set(entryId);
+                        value.set(entry.getEntryBytes(), 0, 
entry.getEntryBytes().length);
+                        dataWriter.append(key, value);
+                        haveOffloadEntryNumber ++;
+                    }
+                } while (haveOffloadEntryNumber - 1 < 
readHandle.getLastAddConfirmed());
+                if (haveOffloadEntryNumber - 1 != 
readHandle.getLastAddConfirmed()) {
+                    log.error("The expected number of entries in offload does 
not match the actual number");
+                    throw new IOException();
+                }
+                IOUtils.closeStream(dataWriter);
+                promise.complete(null);
+            } catch (InterruptedException | ExecutionException | IOException 
e) {
+                log.error("Exception when get 
CompletableFuture<LedgerEntries>. ", e);
+                if (e instanceof InterruptedException) {
+                    Thread.currentThread().interrupt();
+                }
+                promise.completeExceptionally(e);
+                return;
+            }
+        });
+        return promise;
+    }
+
+    @Override
+    public CompletableFuture<ReadHandle> readOffloaded(long ledgerId, UUID 
uuid, Map<String, String> offloadDriverMetadata) {
+
+        CompletableFuture<ReadHandle> promise = new CompletableFuture<>();
+        String storagePath = getStoragePath(storageBasePath, 
offloadDriverMetadata.get("ManagedLedgerName"));
+        String dataFilePath = getDataFilePath(storagePath, ledgerId, uuid);
+        scheduler.chooseThread(ledgerId).submit(() -> {
+            try {
+                MapFile.Reader reader = new MapFile.Reader(new 
Path(dataFilePath),
+                        configuration);
+                
promise.complete(FileStoreBackedReadHandleImpl.open(scheduler.chooseThread(ledgerId),
 reader, ledgerId));
 
 Review comment:
   It seems that we are sharing a scheduler for both reading and writing. If a 
ledger is offloading, then it will be blocked the reading operations. Can we 
use different executors for reading and writing?

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