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https://issues.apache.org/jira/browse/FLINK-8360?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16364133#comment-16364133
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ASF GitHub Bot commented on FLINK-8360:
---------------------------------------
Github user sihuazhou commented on a diff in the pull request:
https://github.com/apache/flink/pull/5239#discussion_r168191066
--- Diff:
flink-runtime/src/main/java/org/apache/flink/runtime/state/TaskLocalStateStoreImpl.java
---
@@ -0,0 +1,298 @@
+/*
+ * 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.flink.runtime.state;
+
+import org.apache.flink.annotation.VisibleForTesting;
+import org.apache.flink.api.common.JobID;
+import org.apache.flink.core.fs.FileSystem;
+import org.apache.flink.core.fs.Path;
+import org.apache.flink.runtime.checkpoint.TaskStateSnapshot;
+import org.apache.flink.runtime.clusterframework.types.AllocationID;
+import org.apache.flink.runtime.jobgraph.JobVertexID;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import javax.annotation.Nonnegative;
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
+import javax.annotation.concurrent.GuardedBy;
+
+import java.io.File;
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.HashMap;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Map;
+import java.util.SortedMap;
+import java.util.TreeMap;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.Executor;
+
+/**
+ * Main implementation of a {@link TaskLocalStateStore}.
+ */
+public class TaskLocalStateStoreImpl implements TaskLocalStateStore {
+
+ /** Logger for this class. */
+ private static final Logger LOG =
LoggerFactory.getLogger(TaskLocalStateStoreImpl.class);
+
+ /** Maximum number of retained snapshots. */
+ @VisibleForTesting
+ static final int MAX_RETAINED_SNAPSHOTS = 5;
+
+ /** Dummy value to use instead of null to satisfy {@link
ConcurrentHashMap}. */
+ private final TaskStateSnapshot NULL_DUMMY = new TaskStateSnapshot();
+
+ /** JobID from the owning subtask. */
+ @Nonnull
+ private final JobID jobID;
+
+ /** AllocationID of the owning slot. */
+ @Nonnull
+ private final AllocationID allocationID;
+
+ /** JobVertexID of the owning subtask. */
+ @Nonnull
+ private final JobVertexID jobVertexID;
+
+ /** Subtask index of the owning subtask. */
+ @Nonnegative
+ private final int subtaskIndex;
+
+ /** The configured mode for local recovery. */
+ @Nonnull
+ private final LocalRecoveryConfig localRecoveryConfig;
+
+ /** Executor that runs the discarding of released state objects. */
+ @Nonnull
+ private final Executor discardExecutor;
+
+ /** Lock for synchronisation on the storage map and the discarded
status. */
+ @Nonnull
+ private final Object lock;
+
+ /** Status flag if this store was already discarded. */
+ @GuardedBy("lock")
+ private boolean discarded;
+
+ /** Maps checkpoint ids to local TaskStateSnapshots. */
+ @Nonnull
+ @GuardedBy("lock")
+ private final SortedMap<Long, TaskStateSnapshot>
storedTaskStateByCheckpointID;
+
+ public TaskLocalStateStoreImpl(
+ @Nonnull JobID jobID,
+ @Nonnull AllocationID allocationID,
+ @Nonnull JobVertexID jobVertexID,
+ @Nonnegative int subtaskIndex,
+ @Nonnull LocalRecoveryConfig localRecoveryConfig,
+ @Nonnull Executor discardExecutor) {
+
+ this.jobID = jobID;
+ this.allocationID = allocationID;
+ this.jobVertexID = jobVertexID;
+ this.subtaskIndex = subtaskIndex;
+ this.discardExecutor = discardExecutor;
+ this.lock = new Object();
+ this.storedTaskStateByCheckpointID = new TreeMap<>();
+ this.discarded = false;
+ this.localRecoveryConfig = localRecoveryConfig;
+ }
+
+ @Override
+ public void storeLocalState(
+ @Nonnegative long checkpointId,
+ @Nullable TaskStateSnapshot localState) {
+
+ if (localState == null) {
+ localState = NULL_DUMMY;
+ }
+
+ LOG.info("Storing local state for checkpoint {}.",
checkpointId);
+ LOG.debug("Local state for checkpoint {} is {}.", checkpointId,
localState);
+
+ Map<Long, TaskStateSnapshot> toDiscard = new
HashMap<>(MAX_RETAINED_SNAPSHOTS);
+
+ synchronized (lock) {
+ if (discarded) {
+ // we ignore late stores and simply discard the
state.
+ toDiscard.put(checkpointId, localState);
+ } else {
+ TaskStateSnapshot previous =
+
storedTaskStateByCheckpointID.put(checkpointId, localState);
+
+ if (previous != null) {
+ toDiscard.put(checkpointId, previous);
+ }
+
+ // remove from history.
+ while (storedTaskStateByCheckpointID.size() >
MAX_RETAINED_SNAPSHOTS) {
+ Long removeCheckpointID =
storedTaskStateByCheckpointID.firstKey();
--- End diff --
If we have to remove local completed checkpoint here, I think
`MAX_RETAINED_SNAPSHOTS` should bigger than `max concurrent checkpoint number.`
> Implement task-local state recovery
> -----------------------------------
>
> Key: FLINK-8360
> URL: https://issues.apache.org/jira/browse/FLINK-8360
> Project: Flink
> Issue Type: New Feature
> Components: State Backends, Checkpointing
> Reporter: Stefan Richter
> Assignee: Stefan Richter
> Priority: Major
> Fix For: 1.5.0
>
>
> This issue tracks the development of recovery from task-local state. The main
> idea is to have a secondary, local copy of the checkpointed state, while
> there is still a primary copy in DFS that we report to the checkpoint
> coordinator.
> Recovery can attempt to restore from the secondary local copy, if available,
> to save network bandwidth. This requires that the assignment from tasks to
> slots is as sticky is possible.
> For starters, we will implement this feature for all managed keyed states and
> can easily enhance it to all other state types (e.g. operator state) later.
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