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ASF GitHub Bot commented on FLINK-8360: --------------------------------------- Github user StefanRRichter commented on a diff in the pull request: https://github.com/apache/flink/pull/5239#discussion_r168528301 --- Diff: flink-runtime/src/main/java/org/apache/flink/runtime/state/TaskLocalStateStore.java --- @@ -19,92 +19,224 @@ package org.apache.flink.runtime.state; import org.apache.flink.api.common.JobID; -import org.apache.flink.runtime.checkpoint.CheckpointMetaData; import org.apache.flink.runtime.checkpoint.TaskStateSnapshot; import org.apache.flink.runtime.jobgraph.JobVertexID; -import org.apache.flink.util.ExceptionUtils; +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.util.HashMap; +import java.util.Arrays; +import java.util.Iterator; import java.util.Map; +import java.util.SortedMap; +import java.util.TreeMap; +import java.util.concurrent.ConcurrentHashMap; +import java.util.concurrent.Executor; /** * This class will service as a task-manager-level local storage for local checkpointed state. The purpose is to provide * access to a state that is stored locally for a faster recovery compared to the state that is stored remotely in a * stable store DFS. For now, this storage is only complementary to the stable storage and local state is typically * lost in case of machine failures. In such cases (and others), client code of this class must fall back to using the * slower but highly available store. - * - * TODO this is currently a placeholder / mock that still must be implemented! */ public class TaskLocalStateStore { - /** */ + /** Logger for this class. */ + private static final Logger LOG = LoggerFactory.getLogger(TaskLocalStateStore.class); + + /** Maximum number of retained snapshots. */ + private 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. */ private final JobID jobID; - /** */ + /** JobVertexID of the owning subtask. */ private final JobVertexID jobVertexID; - /** */ + /** Subtask index of the owning subtask. */ private final int subtaskIndex; - /** */ - private final Map<Long, TaskStateSnapshot> storedTaskStateByCheckpointID; - /** The root directories for all local state of this {@link TaskLocalStateStore}. */ private final File[] localStateRootDirectories; + /** Executor that runs the discarding of released state objects. */ + private final Executor discardExecutor; + + /** Lock for synchronisation on the storage map and the discarded status. */ + private final Object lock; + + /** Status flag if this store was already discarded. */ + @GuardedBy("lock") + private boolean discarded; + + /** Maps checkpoint ids to local TaskStateSnapshots. */ + @GuardedBy("lock") + private final SortedMap<Long, TaskStateSnapshot> storedTaskStateByCheckpointID; + public TaskLocalStateStore( - JobID jobID, - JobVertexID jobVertexID, - int subtaskIndex, - File[] localStateRootDirectories) { + @Nonnull JobID jobID, + @Nonnull JobVertexID jobVertexID, + @Nonnegative int subtaskIndex, + @Nonnull File[] localStateRootDirectories, + @Nonnull Executor discardExecutor) { this.jobID = jobID; this.jobVertexID = jobVertexID; this.subtaskIndex = subtaskIndex; - this.storedTaskStateByCheckpointID = new HashMap<>(); this.localStateRootDirectories = localStateRootDirectories; + this.discardExecutor = discardExecutor; + this.lock = new Object(); + this.storedTaskStateByCheckpointID = new TreeMap<>(); + this.discarded = false; } + @Nonnull protected String createSubtaskPath() { return jobID + File.separator + jobVertexID + File.separator + subtaskIndex; } + /** + * Stores the local state for the given checkpoint id. + * + * @param checkpointId id for the checkpoint that created the local state that will be stored. + * @param localState the local state to store. + */ public void storeLocalState( - @Nonnull CheckpointMetaData checkpointMetaData, + @Nonnegative long checkpointId, @Nullable TaskStateSnapshot localState) { - TaskStateSnapshot previous = - storedTaskStateByCheckpointID.put(checkpointMetaData.getCheckpointId(), localState); + if (localState == null) { + localState = NULL_DUMMY; + } - if (previous != null) { - throw new IllegalStateException("Found previously registered local state for checkpoint with id " + - checkpointMetaData.getCheckpointId() + "! This indicated a problem."); + LOG.info("Storing local state for checkpoint {}.", checkpointId); + LOG.debug("Local state for checkpoint {} is {}.", checkpointId, localState); + + synchronized (lock) { + if (discarded) { + // we ignore late stores and simply discard the state. + discardStateObject(localState, checkpointId); + } else { + TaskStateSnapshot previous = + storedTaskStateByCheckpointID.put(checkpointId, localState); + + if (previous != null) { + // this should never happen. + discardStateObject(previous, checkpointId); + throw new IllegalStateException("Found previously registered local state for checkpoint with id " + + checkpointId + "! This indicated a problem."); + } + + // prune history. + while (storedTaskStateByCheckpointID.size() > MAX_RETAINED_SNAPSHOTS) { + Long removeCheckpointID = storedTaskStateByCheckpointID.firstKey(); + TaskStateSnapshot snapshot = + storedTaskStateByCheckpointID.remove(storedTaskStateByCheckpointID.firstKey()); --- End diff -- Deleted in later commit. > 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. -- This message was sent by Atlassian JIRA (v7.6.3#76005)