org.apache.flink.runtime.state

Interface StateHandle<T>

All Superinterfaces:

Serializable

All Known Subinterfaces:

StreamStateHandle

All Known Implementing Classes:

AsynchronousStateHandle, ByteStreamStateHandle, FileSerializableStateHandle, FileStreamStateHandle, LocalStateHandle, SerializedStateHandle

public interface StateHandle<T>
extends Serializable

StateHandle is a general handle interface meant to abstract operator state fetching. A StateHandle implementation can for example include the state itself in cases where the state is lightweight or fetching it lazily from some external storage when the state is too large.

Method Summary

Methods

Modifier and Type	Method and Description
void	discardState() Discards the state referred to by this handle, to free up resources in the persistent storage.
T	getState(ClassLoader userCodeClassLoader) This retrieves and return the state represented by the handle.
long	getStateSize() Returns the size of the state in bytes.

Method Detail

getState

T getState(ClassLoader userCodeClassLoader)
           throws Exception

This retrieves and return the state represented by the handle.

Parameters:

userCodeClassLoader - Class loader for deserializing user code specific classes

Returns:

The state represented by the handle.

Throws:

Exception - Thrown, if the state cannot be fetched.

discardState

void discardState()
                  throws Exception

Discards the state referred to by this handle, to free up resources in the persistent storage. This method is called when the handle will not be used any more.

Throws:

Exception

getStateSize

long getStateSize()
                  throws Exception

Returns the size of the state in bytes.

If the the size is not known, return 0.

Returns:

Size of the state in bytes.

Throws:

Exception - If the operation fails during size retrieval.