Package org.apache.flink.util

Class FileLock

java.lang.Object

org.apache.flink.util.FileLock

@Internal
public class FileLock
extends Object

A file lock used for avoiding race condition among multiple threads/processes.

Constructor Summary

Constructors

Constructor	Description
FileLock(String fullPath)	Initialize a FileLock using a file located at fullPath.
FileLock(String parentDir, String fileName)	Initialize a FileLock using a file located at parentDir/fileName.

Method Summary

Modifier and Type	Method	Description
static FileLock	inTempFolder(String fileName)	Initialize a FileLock using a file located inside temp folder.
boolean	isValid()	Check whether a FileLock is actually holding the lock.
boolean	tryLock()	Try to acquire a lock on the locking file.
void	unlock()	Release the file lock.
void	unlockAndDestroy()	Release the file lock, close the fileChannel and FileOutputStream then try deleting the locking file if other file lock does not need it, which means the lock will not be used anymore.

Methods inherited from class java.lang.Object

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

Constructor Detail

FileLock

public FileLock(String fullPath)

Initialize a FileLock using a file located at fullPath.

Parameters:

fullPath - The path of the locking file

FileLock

public FileLock(String parentDir,
                String fileName)

Initialize a FileLock using a file located at parentDir/fileName.

Parameters:

parentDir - The parent dir of the locking file

fileName - The name of the locking file

Method Detail

inTempFolder

public static FileLock inTempFolder(String fileName)

Initialize a FileLock using a file located inside temp folder.

Parameters:

fileName - The name of the locking file

Returns:

The initialized FileLock

tryLock

public boolean tryLock()
                throws IOException

Try to acquire a lock on the locking file. This method immediately returns whenever the lock is acquired or not.

Returns:

True if successfully acquired the lock

Throws:

IOException - If the file path is invalid

unlock

public void unlock()
            throws IOException

Release the file lock.

Throws:

IOException - If the FileChannel is closed

unlockAndDestroy

public void unlockAndDestroy()
                      throws IOException

Release the file lock, close the fileChannel and FileOutputStream then try deleting the locking file if other file lock does not need it, which means the lock will not be used anymore.

Throws:

IOException - If an I/O error occurs

isValid

public boolean isValid()

Check whether a FileLock is actually holding the lock.

Returns:

True if it is actually holding the lock