org.apache.flink.runtime.checkpoint

Class TaskStateSnapshot

java.lang.Object

org.apache.flink.runtime.checkpoint.TaskStateSnapshot

All Implemented Interfaces:

Serializable, CompositeStateHandle, StateObject

public class TaskStateSnapshot
extends Object
implements CompositeStateHandle

This class encapsulates state handles to the snapshots of all operator instances executed within one task. A task can run multiple operator instances as a result of operator chaining, and all operator instances from the chain can register their state under their operator id. Each operator instance is a physical execution responsible for processing a partition of the data that goes through a logical operator. This partitioning happens to parallelize execution of logical operators, e.g. distributing a map function.

One instance of this class contains the information that one task will send to acknowledge a checkpoint request by the checkpoint coordinator. Tasks run operator instances in parallel, so the union of all TaskStateSnapshot that are collected by the checkpoint coordinator from all tasks represent the whole state of a job at the time of the checkpoint.

This class should be called TaskState once the old class with this name that we keep for backwards compatibility goes away.

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
TaskStateSnapshot()
TaskStateSnapshot(int size)
TaskStateSnapshot(Map<OperatorID,OperatorSubtaskState> subtaskStatesByOperatorID)

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.
boolean	equals(Object o)
long	getStateSize() Returns the size of the state in bytes.
OperatorSubtaskState	getSubtaskStateByOperatorID(OperatorID operatorID) Returns the subtask state for the given operator id (or null if not contained).
Set<Map.Entry<OperatorID,OperatorSubtaskState>>	getSubtaskStateMappings() Returns the set of all mappings from operator id to the corresponding subtask state.
int	hashCode()
boolean	hasState() Returns true if at least one OperatorSubtaskState in subtaskStatesByOperatorID has state.
OperatorSubtaskState	putSubtaskStateByOperatorID(OperatorID operatorID, OperatorSubtaskState state) Maps the given operator id to the given subtask state.
void	registerSharedStates(SharedStateRegistry stateRegistry) Register both newly created and already referenced shared states in the given SharedStateRegistry.
String	toString()

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Constructor Detail

TaskStateSnapshot

public TaskStateSnapshot()

TaskStateSnapshot

public TaskStateSnapshot(int size)

TaskStateSnapshot

public TaskStateSnapshot(Map<OperatorID,OperatorSubtaskState> subtaskStatesByOperatorID)

Method Detail

getSubtaskStateByOperatorID

@Nullable
public OperatorSubtaskState getSubtaskStateByOperatorID(OperatorID operatorID)

Returns the subtask state for the given operator id (or null if not contained).

putSubtaskStateByOperatorID

public OperatorSubtaskState putSubtaskStateByOperatorID(@Nonnull
                                                        OperatorID operatorID,
                                                        @Nonnull
                                                        OperatorSubtaskState state)

Maps the given operator id to the given subtask state. Returns the subtask state of a previous mapping, if such a mapping existed or null otherwise.

getSubtaskStateMappings

public Set<Map.Entry<OperatorID,OperatorSubtaskState>> getSubtaskStateMappings()

Returns the set of all mappings from operator id to the corresponding subtask state.

hasState

public boolean hasState()

Returns true if at least one OperatorSubtaskState in subtaskStatesByOperatorID has state.

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 any more.

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.

registerSharedStates

public void registerSharedStates(SharedStateRegistry stateRegistry)

Description copied from interface: CompositeStateHandle

Register both newly created and already referenced shared states in the given SharedStateRegistry. This method is called when the checkpoint successfully completes or is recovered from failures.

After this is completed, newly created shared state is considered as published is no longer owned by this handle. This means that it should no longer be deleted as part of calls to StateObject.discardState(). Instead, StateObject.discardState() will trigger an unregistration from the registry.

Specified by:

registerSharedStates in interface CompositeStateHandle

Parameters:

stateRegistry - The registry where shared states are registered.

equals

public boolean equals(Object o)

Overrides:

equals in class Object

hashCode

public int hashCode()

Overrides:

hashCode in class Object

toString

public String toString()

Overrides:

toString in class Object