org.apache.flink.runtime.state

Class PlaceholderStreamStateHandle

java.lang.Object

org.apache.flink.runtime.state.PlaceholderStreamStateHandle

All Implemented Interfaces:

Serializable, StateObject, StreamStateHandle

public class PlaceholderStreamStateHandle
extends Object
implements StreamStateHandle

A placeholder state handle for shared state that will replaced by an original that was created in a previous checkpoint. So we don't have to send a state handle twice, e.g. in case of ByteStreamStateHandle. This class is used in the referenced states of IncrementalKeyedStateHandle.

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
PlaceholderStreamStateHandle()

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.
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.

Methods inherited from class java.lang.Object

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

Constructor Detail

PlaceholderStreamStateHandle

public PlaceholderStreamStateHandle()

Method Detail

openInputStream

public FSDataInputStream openInputStream()

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

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.