Package org.apache.nutch.util

Class LockUtil

java.lang.Object

org.apache.nutch.util.LockUtil

public class LockUtil
extends Object

Utility methods for handling application-level locking.

Author:

Andrzej Bialecki

Constructor Summary

Constructors

Constructor	Description
LockUtil()

Method Summary

Modifier and Type	Method	Description
static void	createLockFile(Configuration conf, Path lockFile, boolean accept)	Create a lock file.
static void	createLockFile(FileSystem fs, Path lockFile, boolean accept)	Create a lock file.
static boolean	removeLockFile(Configuration conf, Path lockFile)	Remove lock file.
static boolean	removeLockFile(FileSystem fs, Path lockFile)	Remove lock file.

Methods inherited from class java.lang.Object

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

Constructor Detail

LockUtil

public LockUtil()

Method Detail

createLockFile

public static void createLockFile(FileSystem fs,
                                  Path lockFile,
                                  boolean accept)
                           throws IOException

Create a lock file.

Parameters:

fs - filesystem

lockFile - name of the lock file

accept - if true, and the target file exists, consider it valid. If false and the target file exists, throw an IOException.

Throws:

IOException - if accept is false, and the target file already exists, or if it's a directory.

createLockFile

public static void createLockFile(Configuration conf,
                                  Path lockFile,
                                  boolean accept)
                           throws IOException

Create a lock file.

Parameters:

conf - configuration to find the FileSystem lockFile belongs to

lockFile - name of the lock file

accept - if true, and the target file exists, consider it valid. If false and the target file exists, throw an IOException.

Throws:

IOException - if accept is false, and the target file already exists, or if it's a directory.

removeLockFile

public static boolean removeLockFile(FileSystem fs,
                                     Path lockFile)
                              throws IOException

Remove lock file. NOTE: applications enforce the semantics of this file - this method simply removes any file with a given name.

Parameters:

fs - filesystem

lockFile - lock file name

Returns:

false, if the lock file doesn't exist. True, if it existed and was successfully removed.

Throws:

IOException - if lock file exists but it is a directory.

removeLockFile

public static boolean removeLockFile(Configuration conf,
                                     Path lockFile)
                              throws IOException

Remove lock file. NOTE: applications enforce the semantics of this file - this method simply removes any file with a given name.

Parameters:

conf - configuration to find the FileSystem lockFile belongs to

lockFile - lock file name

Returns:

false, if the lock file doesn't exist. True, if it existed and was successfully removed.

Throws:

IOException - if lock file exists but it is a directory.