org.apache.flink.runtime.state.filesystem

Class FileBasedStateOutputStream

java.lang.Object

java.io.OutputStream

org.apache.flink.core.fs.FSDataOutputStream

org.apache.flink.runtime.state.CheckpointStreamFactory.CheckpointStateOutputStream

org.apache.flink.runtime.state.filesystem.FileBasedStateOutputStream

All Implemented Interfaces:

Closeable, Flushable, AutoCloseable

public final class FileBasedStateOutputStream
extends CheckpointStreamFactory.CheckpointStateOutputStream

A CheckpointStreamFactory.CheckpointStateOutputStream that writes into a specified file and returns a FileStateHandle upon closing.

Unlike the FsCheckpointStreamFactory.FsCheckpointStateOutputStream, this stream does not have a threshold below which it returns a memory byte stream handle, and does not create random files, but writes to a specified file.

Constructor Summary

Constructors

Constructor and Description
FileBasedStateOutputStream(FileSystem fileSystem, Path path)

Method Summary

Modifier and Type	Method and Description
void	close() This method should close the stream, if has not been closed before.
FileStateHandle	closeAndGetHandle() Closes the stream and gets a state handle that can create an input stream producing the data written to this stream.
void	flush() Flushes the stream, writing any data currently buffered in stream implementation to the proper output stream.
long	getPos() Gets the position of the stream (non-negative), defined as the number of bytes from the beginning of the file to the current writing position.
boolean	isClosed()
void	sync() Flushes the data all the way to the persistent non-volatile storage (for example disks).
void	write(byte[] b, int off, int len)
void	write(int b)

Methods inherited from class java.io.OutputStream

write

Methods inherited from class java.lang.Object

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

Constructor Detail

FileBasedStateOutputStream

public FileBasedStateOutputStream(FileSystem fileSystem,
                                  Path path)
                           throws IOException

Throws:

IOException

Method Detail

write

public final void write(int b)
                 throws IOException

Specified by:

write in class OutputStream

Throws:

IOException

write

public final void write(@Nonnull
                        byte[] b,
                        int off,
                        int len)
                 throws IOException

Overrides:

write in class OutputStream

Throws:

IOException

getPos

public long getPos()
            throws IOException

Description copied from class: FSDataOutputStream

Gets the position of the stream (non-negative), defined as the number of bytes from the beginning of the file to the current writing position. The position corresponds to the zero-based index of the next byte that will be written.

This method must report accurately report the current position of the stream. Various components of the high-availability and recovery logic rely on the accurate

Specified by:

getPos in class FSDataOutputStream

Returns:

The current position in the stream, defined as the number of bytes from the beginning of the file to the current writing position.

Throws:

IOException - Thrown if an I/O error occurs while obtaining the position from the stream implementation.

flush

public void flush()
           throws IOException

Description copied from class: FSDataOutputStream

Flushes the stream, writing any data currently buffered in stream implementation to the proper output stream. After this method has been called, the stream implementation must not hold onto any buffered data any more.

A completed flush does not mean that the data is necessarily persistent. Data persistence can is only assumed after calls to FSDataOutputStream.close() or FSDataOutputStream.sync().

Implementation note: This overrides the method defined in OutputStream as abstract to force implementations of the FSDataOutputStream to implement this method directly.

Specified by:

flush in interface Flushable

Specified by:

flush in class FSDataOutputStream

Throws:

IOException - Thrown if an I/O error occurs while flushing the stream.

sync

public void sync()
          throws IOException

Description copied from class: FSDataOutputStream

Flushes the data all the way to the persistent non-volatile storage (for example disks). The method behaves similar to the fsync function, forcing all data to be persistent on the devices.

Specified by:

sync in class FSDataOutputStream

Throws:

IOException - Thrown if an I/O error occurs

isClosed

public boolean isClosed()

close

public void close()

Description copied from class: CheckpointStreamFactory.CheckpointStateOutputStream

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 CheckpointStreamFactory.CheckpointStateOutputStream.closeAndGetHandle().

Specified by:

close in interface Closeable

Specified by:

close in interface AutoCloseable

Specified by:

close in class CheckpointStreamFactory.CheckpointStateOutputStream

closeAndGetHandle

@Nullable
public FileStateHandle closeAndGetHandle()
                                            throws IOException

Description copied from class: CheckpointStreamFactory.CheckpointStateOutputStream

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 CheckpointStreamFactory.CheckpointStateOutputStream.close() method removes the target resource when called.

Specified by:

closeAndGetHandle in class CheckpointStreamFactory.CheckpointStateOutputStream

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.