org.apache.storm.hdfs.spout

Class DirLock

java.lang.Object

org.apache.storm.hdfs.spout.DirLock

public class DirLock
extends Object

Facility to synchronize access to HDFS directory. The lock itself is represented as a file in the same directory. Relies on atomic file creation.

Field Summary

Fields

Modifier and Type	Field and Description
static String	DIR_LOCK_FILE

Method Summary

Modifier and Type	Method and Description
org.apache.hadoop.fs.Path	getLockFile()
void	release() Release lock on dir by deleting the lock file
static DirLock	takeOwnershipIfStale(org.apache.hadoop.fs.FileSystem fs, org.apache.hadoop.fs.Path dirToLock, int lockTimeoutSec) if the lock on the directory is stale, take ownership
static DirLock	tryLock(org.apache.hadoop.fs.FileSystem fs, org.apache.hadoop.fs.Path dir) Get a lock on file if not already locked

Methods inherited from class java.lang.Object

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

Field Detail

DIR_LOCK_FILE

public static final String DIR_LOCK_FILE

See Also:

Constant Field Values

Method Detail

tryLock

public static DirLock tryLock(org.apache.hadoop.fs.FileSystem fs,
                              org.apache.hadoop.fs.Path dir)
                       throws IOException

Get a lock on file if not already locked

Parameters:

fs -

dir - the dir on which to get a lock

Returns:

The lock object if it the lock was acquired. Returns null if the dir is already locked.

Throws:

IOException - if there were errors

release

public void release()
             throws IOException

Release lock on dir by deleting the lock file

Throws:

IOException

takeOwnershipIfStale

public static DirLock takeOwnershipIfStale(org.apache.hadoop.fs.FileSystem fs,
                                           org.apache.hadoop.fs.Path dirToLock,
                                           int lockTimeoutSec)

if the lock on the directory is stale, take ownership

getLockFile

public org.apache.hadoop.fs.Path getLockFile()