org.apache.flink.runtime.state

Class SnapshotResult<T extends StateObject>

java.lang.Object

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

All Implemented Interfaces:

Serializable, StateObject

public class SnapshotResult<T extends StateObject>
extends Object
implements StateObject

This class contains the combined results from the snapshot of a state backend:

• A state object representing the state that will be reported to the Job Manager to acknowledge the checkpoint.
• A state object that represents the state for the TaskLocalStateStoreImpl.

Both state objects are optional and can be null, e.g. if there was no state to snapshot in the backend. A local state object that is not null also requires a state to report to the job manager that is not null, because the Job Manager always owns the ground truth about the checkpointed state.

See Also:

Serialized Form

Nested Class Summary

Nested classes/interfaces inherited from interface org.apache.flink.runtime.state.StateObject

StateObject.StateObjectLocation, StateObject.StateObjectSizeStatsCollector

Method Summary

Modifier and Type	Method and Description
void	discardState() Discards the state referred to and solemnly owned by this handle, to free up resources in the persistent storage.
static <T extends StateObject> SnapshotResult<T>	empty()
T	getJobManagerOwnedSnapshot()
long	getStateSize() Returns the size of the state in bytes.
T	getTaskLocalSnapshot()
static <T extends StateObject> SnapshotResult<T>	of(T jobManagerState)
static <T extends StateObject> SnapshotResult<T>	withLocalState(T jobManagerState, T localState)

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.apache.flink.runtime.state.StateObject

collectSizeStats

Method Detail

getJobManagerOwnedSnapshot

@Nullable
public T getJobManagerOwnedSnapshot()

getTaskLocalSnapshot

@Nullable
public T getTaskLocalSnapshot()

discardState

public void discardState()
                  throws Exception

Description copied from interface: StateObject

Discards the state referred to and solemnly owned by this handle, to free up resources in the persistent storage. This method is called when the state represented by this object will not be used anymore.

Specified by:

discardState in interface StateObject

Throws:

Exception

getStateSize

public long getStateSize()

Description copied from interface: StateObject

Returns the size of the state in bytes. If the size is not known, this method should return 0.

The values produced by this method are only used for informational purposes and for metrics/monitoring. If this method returns wrong values, the checkpoints and recovery will still behave correctly. However, efficiency may be impacted (wrong space pre-allocation) and functionality that depends on metrics (like monitoring) will be impacted.

Note for implementors: This method should not perform any I/O operations while obtaining the state size (hence it does not declare throwing an IOException). Instead, the state size should be stored in the state object, or should be computable from the state stored in this object. The reason is that this method is called frequently by several parts of the checkpointing and issuing I/O requests from this method accumulates a heavy I/O load on the storage system at higher scale.

Specified by:

getStateSize in interface StateObject

Returns:

Size of the state in bytes.

empty

public static <T extends StateObject> SnapshotResult<T> empty()

of

public static <T extends StateObject> SnapshotResult<T> of(@Nullable
                                                           T jobManagerState)

withLocalState

public static <T extends StateObject> SnapshotResult<T> withLocalState(@Nonnull
                                                                       T jobManagerState,
                                                                       @Nonnull
                                                                       T localState)