org.apache.hadoop.hbase.io

Class FileChangeWatcher

java.lang.Object

org.apache.hadoop.hbase.io.FileChangeWatcher

@InterfaceAudience.Private
public final class FileChangeWatcher
extends Object

Instances of this class can be used to watch a directory for file changes. When a file is added to, deleted from, or is modified in the given directory, the callback provided by the user will be called from a background thread. Some things to keep in mind:

• The callback should be thread-safe.
• Changes that happen around the time the thread is started may be missed.
• There is a delay between a file changing and the callback firing.
• The watch is not recursive - changes to subdirectories will not trigger a callback.

This file has been copied from the Apache ZooKeeper project.

See Also:

Base revision

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	FileChangeWatcher.State

Constructor Summary

Constructors

Constructor and Description
FileChangeWatcher(Path dirPath, String threadNameSuffix, Consumer<WatchEvent<?>> callback) Creates a watcher that watches dirPath and invokes callback on changes.

Method Summary

Modifier and Type	Method and Description
FileChangeWatcher.State	getState() Returns the current FileChangeWatcher.State.
void	start() Tells the background thread to start.
void	stop() Tells the background thread to stop.

Methods inherited from class java.lang.Object

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

Constructor Detail

FileChangeWatcher

public FileChangeWatcher(Path dirPath,
                         String threadNameSuffix,
                         Consumer<WatchEvent<?>> callback)
                  throws IOException

Creates a watcher that watches dirPath and invokes callback on changes.

Parameters:

dirPath - the directory to watch.

callback - the callback to invoke with events. event.kind() will return the type of event, and event.context() will return the filename relative to dirPath.

Throws:

IOException - if there is an error creating the WatchService.

Method Detail

getState

public FileChangeWatcher.State getState()

Returns the current FileChangeWatcher.State.

Returns:

the current state.

start

public void start()

Tells the background thread to start. Does not wait for it to be running. Calling this method more than once has no effect.

stop

public void stop()

Tells the background thread to stop. Does not wait for it to exit.