org.apache.flink.runtime.state

Class SharedStateRegistry

java.lang.Object

org.apache.flink.runtime.state.SharedStateRegistry

All Implemented Interfaces:

AutoCloseable

public class SharedStateRegistry
extends Object
implements AutoCloseable

This registry manages state that is shared across (incremental) checkpoints, and is responsible for deleting shared state that is no longer used in any valid checkpoint. A SharedStateRegistry will be deployed in the CheckpointCoordinator to maintain the reference count of StreamStateHandles by a key that (logically) identifies them.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	SharedStateRegistry.Result The result of an attempt to (un)/reference state

Field Summary

Fields

Modifier and Type	Field and Description
static SharedStateRegistryFactory	DEFAULT_FACTORY A singleton object for the default implementation of a SharedStateRegistryFactory

Constructor Summary

Constructors

Constructor and Description
SharedStateRegistry() Default uses direct executor to delete unreferenced state
SharedStateRegistry(Executor asyncDisposalExecutor)

Method Summary

Modifier and Type	Method and Description
void	close()
void	registerAll(Iterable<? extends CompositeStateHandle> stateHandles) Register given shared states in the registry.
SharedStateRegistry.Result	registerReference(SharedStateRegistryKey registrationKey, StreamStateHandle state) Register a reference to the given shared state in the registry.
String	toString()
SharedStateRegistry.Result	unregisterReference(SharedStateRegistryKey registrationKey) Releases one reference to the given shared state in the registry.

Methods inherited from class java.lang.Object

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

Field Detail

DEFAULT_FACTORY

public static final SharedStateRegistryFactory DEFAULT_FACTORY

A singleton object for the default implementation of a SharedStateRegistryFactory

Constructor Detail

SharedStateRegistry

public SharedStateRegistry()

Default uses direct executor to delete unreferenced state

SharedStateRegistry

public SharedStateRegistry(Executor asyncDisposalExecutor)

Method Detail

registerReference

public SharedStateRegistry.Result registerReference(SharedStateRegistryKey registrationKey,
                                                    StreamStateHandle state)

Register a reference to the given shared state in the registry. This does the following: We check if the state handle is actually new by the registrationKey. If it is new, we register it with a reference count of 1. If there is already a state handle registered under the given key, we dispose the given "new" state handle, uptick the reference count of the previously existing state handle and return it as a replacement with the result.

IMPORTANT: caller should check the state handle returned by the result, because the registry is performing de-duplication and could potentially return a handle that is supposed to replace the one from the registration request.

Parameters:

state - the shared state for which we register a reference.

Returns:

the result of this registration request, consisting of the state handle that is registered under the key by the end of the operation and its current reference count.

unregisterReference

public SharedStateRegistry.Result unregisterReference(SharedStateRegistryKey registrationKey)

Releases one reference to the given shared state in the registry. This decreases the reference count by one. Once the count reaches zero, the shared state is deleted.

Parameters:

registrationKey - the shared state for which we release a reference.

Returns:

the result of the request, consisting of the reference count after this operation and the state handle, or null if the state handle was deleted through this request. Returns null if the registry was previously closed.

registerAll

public void registerAll(Iterable<? extends CompositeStateHandle> stateHandles)

Register given shared states in the registry.

Parameters:

stateHandles - The shared states to register.

toString

public String toString()

Overrides:

toString in class Object

close

public void close()

Specified by:

close in interface AutoCloseable