Package 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	Description
static final String	DIR_LOCK_FILE

Method Summary

Modifier and Type	Method	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 Details

DIR_LOCK_FILE

public static final String DIR_LOCK_FILE

See Also:

• Constant Field Values

Method Details

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:

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

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.

release

public void release()
             throws IOException

Release lock on dir by deleting the lock file.

Throws:

IOException

getLockFile

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