Package org.apache.flink.runtime.state

Class CheckpointStateOutputStream

java.lang.Object

java.io.OutputStream

org.apache.flink.core.fs.FSDataOutputStream

org.apache.flink.runtime.state.CheckpointStateOutputStream

All Implemented Interfaces:

Closeable, Flushable, AutoCloseable

Direct Known Subclasses:

DuplicatingCheckpointOutputStream, FileBasedStateOutputStream, FsCheckpointStreamFactory.FsCheckpointStateOutputStream, MemCheckpointStreamFactory.MemoryCheckpointOutputStream

@Internal
public abstract class CheckpointStateOutputStream
extends org.apache.flink.core.fs.FSDataOutputStream

A dedicated output stream that produces a StreamStateHandle when closed.

Important: When closing this stream after the successful case, you must call closeAndGetHandle() - only that method will actually retain the resource written to. The method has the semantics of "close on success". The close() method is supposed to remove the target resource if called before closeAndGetHandle(), hence having the semantics of "close on failure". That way, simple try-with-resources statements automatically clean up unsuccessful partial state resources in case the writing does not complete.

Note: This is an abstract class and not an interface because OutputStream is an abstract class.

Constructor Summary

Constructors

Constructor	Description
CheckpointStateOutputStream()

Method Summary

Modifier and Type	Method	Description
abstract void	close()	This method should close the stream, if has not been closed before.
abstract StreamStateHandle	closeAndGetHandle()	Closes the stream and gets a state handle that can create an input stream producing the data written to this stream.

Methods inherited from class org.apache.flink.core.fs.FSDataOutputStream

flush, getPos, sync

Methods inherited from class java.io.OutputStream

nullOutputStream, write, write, write

Methods inherited from class java.lang.Object

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

Constructor Details

CheckpointStateOutputStream

public CheckpointStateOutputStream()

Method Details

closeAndGetHandle

@Nullable
public abstract StreamStateHandle closeAndGetHandle()
                                             throws IOException

Closes the stream and gets a state handle that can create an input stream producing the data written to this stream.

This closing must be called (also when the caller is not interested in the handle) to successfully close the stream and retain the produced resource. In contrast, the close() method removes the target resource when called.

Returns:

A state handle that can create an input stream producing the data written to this stream.

Throws:

IOException - Thrown, if the stream cannot be closed.

close

public abstract void close()
                    throws IOException

This method should close the stream, if has not been closed before. If this method actually closes the stream, it should delete/release the resource behind the stream, such as the file that the stream writes to.

The above implies that this method is intended to be the "unsuccessful close", such as when cancelling the stream writing, or when an exception occurs. Closing the stream for the successful case must go through closeAndGetHandle().

Specified by:

close in interface AutoCloseable

Specified by:

close in interface Closeable

Specified by:

close in class org.apache.flink.core.fs.FSDataOutputStream

Throws:

IOException - Thrown, if the stream cannot be closed.