org.apache.flink.runtime.state

Class AsyncSnapshotCallable<T>

java.lang.Object

org.apache.flink.runtime.state.AsyncSnapshotCallable<T>

Type Parameters:

T - type of the result.

All Implemented Interfaces:

Callable<T>

public abstract class AsyncSnapshotCallable<T>
extends Object
implements Callable<T>

Base class that outlines the strategy for asynchronous snapshots. Implementations of this class are typically instantiated with resources that have been created in the synchronous part of a snapshot. Then, the implementation of callInternal() is invoked in the asynchronous part. All resources created by this methods should be released by the end of the method. If the created resources are Closeable objects and can block in calls (e.g. in/output streams), they should be registered with the snapshot's CloseableRegistry so that the can be closed and unblocked on cancellation. After callInternal() ended, logAsyncSnapshotComplete(long) is called. In that method, implementations can emit log statements about the duration. At the very end, this class calls cleanupProvidedResources(). The implementation of this method should release all provided resources that have been passed into the snapshot from the synchronous part of the snapshot.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
class	AsyncSnapshotCallable.AsyncSnapshotTask FutureTask that wraps a AsyncSnapshotCallable and connects it with cancellation and closing.

Field Summary

Fields

Modifier and Type	Field and Description
protected CloseableRegistry	snapshotCloseableRegistry Registers streams that can block in I/O during snapshot.

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	AsyncSnapshotCallable()

Method Summary

Modifier and Type	Method and Description
T	call()
protected abstract T	callInternal() This method implements the (async) snapshot logic.
protected void	cancel()
protected abstract void	cleanupProvidedResources() This method implements the cleanup of resources that have been passed in (from the sync part).
protected void	logAsyncSnapshotComplete(long startTime) This method is invoked after completion of the snapshot and can be overridden to output a logging about the duration of the async part.
AsyncSnapshotCallable.AsyncSnapshotTask	toAsyncSnapshotFutureTask(CloseableRegistry taskRegistry) Creates a future task from this and registers it with the given CloseableRegistry.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

snapshotCloseableRegistry

@Nonnull
protected final CloseableRegistry snapshotCloseableRegistry

Registers streams that can block in I/O during snapshot. Forwards close from taskCancelCloseableRegistry.

Constructor Detail

AsyncSnapshotCallable

protected AsyncSnapshotCallable()

Method Detail

call

public T call()
       throws Exception

Specified by:

call in interface Callable<T>

Throws:

Exception

cancel

@VisibleForTesting
protected void cancel()

toAsyncSnapshotFutureTask

public AsyncSnapshotCallable.AsyncSnapshotTask toAsyncSnapshotFutureTask(@Nonnull
                                                                         CloseableRegistry taskRegistry)
                                                                  throws IOException

Creates a future task from this and registers it with the given CloseableRegistry. The task is unregistered again in FutureTask.done().

Throws:

IOException

callInternal

protected abstract T callInternal()
                           throws Exception

This method implements the (async) snapshot logic. Resources aquired within this method should be released at the end of the method.

Throws:

Exception

cleanupProvidedResources

protected abstract void cleanupProvidedResources()

This method implements the cleanup of resources that have been passed in (from the sync part). Called after the end of callInternal().

logAsyncSnapshotComplete

protected void logAsyncSnapshotComplete(long startTime)

This method is invoked after completion of the snapshot and can be overridden to output a logging about the duration of the async part.