Package org.apache.flink.runtime.state

Class ChainedStateHandle<T extends StateObject>

java.lang.Object

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

All Implemented Interfaces:

Serializable, StateObject

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

Handle to state handles for the operators in an operator chain.

See Also:

Serialized Form

Nested Class Summary

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

StateObject.StateObjectLocation, StateObject.StateObjectSizeStatsCollector

Constructor Summary

Constructors

Constructor	Description
ChainedStateHandle(List<? extends T> operatorStateHandles)	Wraps a list to the state handles for the operators in a chain.

Method Summary

Modifier and Type	Method	Description
void	collectSizeStats(StateObject.StateObjectSizeStatsCollector collector)	Collects statistics about state size and location from the state object.
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)
T	get(int index)	Get the state handle for a single operator in the operator chain by it's index.
int	getLength()	Returns the length of the operator chain.
long	getStateSize()	Returns the size of the state in bytes.
int	hashCode()
boolean	isEmpty()	Check if there are any states handles present.
static boolean	isNullOrEmpty(ChainedStateHandle<?> chainedStateHandle)
static <T extends StateObject> ChainedStateHandle<T>	wrapSingleHandle(T stateHandleToWrap)

Methods inherited from class java.lang.Object

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

Constructor Detail

ChainedStateHandle

public ChainedStateHandle(List<? extends T> operatorStateHandles)

Wraps a list to the state handles for the operators in a chain. Individual state handles can be null.

Parameters:

operatorStateHandles - list with the state handles for the states in the operator chain.

Method Detail

isEmpty

public boolean isEmpty()

Check if there are any states handles present. Notice that this can be true even if getLength() is greater than zero, because state handles can be null.

Returns:

true if there are no state handles for any operator.

getLength

public int getLength()

Returns the length of the operator chain. This can be different from the number of operator state handles, because the some operators in the chain can have no state and thus their state handle can be null.

Returns:

length of the operator chain

get

public T get(int index)

Get the state handle for a single operator in the operator chain by it's index.

Parameters:

index - the index in the operator chain

Returns:

state handle to the operator at the given position in the operator chain. can be null.

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.

collectSizeStats

public void collectSizeStats(StateObject.StateObjectSizeStatsCollector collector)

Description copied from interface: StateObject

Collects statistics about state size and location from the state object.

Specified by:

collectSizeStats in interface StateObject

Parameters:

collector - the statistics collector.

equals

public boolean equals(Object o)

Overrides:

equals in class Object

hashCode

public int hashCode()

Overrides:

hashCode in class Object

wrapSingleHandle

public static <T extends StateObject> ChainedStateHandle<T> wrapSingleHandle(T stateHandleToWrap)

isNullOrEmpty

public static boolean isNullOrEmpty(ChainedStateHandle<?> chainedStateHandle)