org.apache.flink.runtime.state

Class RetrievableStreamStateHandle<T extends Serializable>

java.lang.Object

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

Type Parameters:

T - type of the retrievable object which is stored under the wrapped stream handle

All Implemented Interfaces:

Closeable, Serializable, AutoCloseable, RetrievableStateHandle<T>, StateObject, StreamStateHandle

public class RetrievableStreamStateHandle<T extends Serializable>
extends Object
implements StreamStateHandle, RetrievableStateHandle<T>, Closeable

Wrapper around a StreamStateHandle to make the referenced state object retrievable trough a simple get call. This implementation expects that the object was serialized through default serialization of Java's ObjectOutputStream.

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
RetrievableStreamStateHandle(Path filePath, long stateSize)
RetrievableStreamStateHandle(StreamStateHandle streamStateHandle)

Method Summary

Modifier and Type	Method and Description
void	close()
void	discardState() Discards the state referred to and solemnly owned by this handle, to free up resources in the persistent storage.
long	getStateSize() Returns the size of the state in bytes.
FSDataInputStream	openInputStream() Returns an FSDataInputStream that can be used to read back the data that was previously written to the stream.
T	retrieveState() Retrieves the object that was previously written to state.

Methods inherited from class java.lang.Object

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

Constructor Detail

RetrievableStreamStateHandle

public RetrievableStreamStateHandle(StreamStateHandle streamStateHandle)

RetrievableStreamStateHandle

public RetrievableStreamStateHandle(Path filePath,
                                    long stateSize)

Method Detail

retrieveState

public T retrieveState()
                throws IOException,
                       ClassNotFoundException

Description copied from interface: RetrievableStateHandle

Retrieves the object that was previously written to state.

Specified by:

retrieveState in interface RetrievableStateHandle<T extends Serializable>

Throws:

IOException

ClassNotFoundException

openInputStream

public FSDataInputStream openInputStream()
                                  throws IOException

Description copied from interface: StreamStateHandle

Returns an FSDataInputStream that can be used to read back the data that was previously written to the stream.

Specified by:

openInputStream in interface StreamStateHandle

Throws:

IOException

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.

close

public void close()
           throws IOException

Specified by:

close in interface Closeable

Specified by:

close in interface AutoCloseable

Throws:

IOException