org.apache.flink.runtime.state

Class SharedStateRegistry

java.lang.Object

org.apache.flink.runtime.state.SharedStateRegistry

public class SharedStateRegistry
extends Object

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

Constructor Summary

Constructors

Constructor and Description
SharedStateRegistry()
SharedStateRegistry(Executor asyncDisposalExecutor)

Method Summary

Methods

Modifier and Type	Method and Description
void	clear() Clears the registry.
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.
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, toString, wait, wait, wait

Constructor Detail

SharedStateRegistry

public SharedStateRegistry()

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 oepration 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.

registerAll

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

Register given shared states in the registry.

Parameters:

stateHandles - The shared states to register.

clear

public void clear()

Clears the registry.