Package org.apache.druid.curator.announcement

Class PathChildrenAnnouncer

java.lang.Object

org.apache.druid.curator.announcement.PathChildrenAnnouncer

All Implemented Interfaces:

ServiceAnnouncer

public class PathChildrenAnnouncer
extends Object
implements ServiceAnnouncer

The PathChildrenAnnouncer class manages the announcement of a node, and watches all child and sibling nodes under the specified path in a ZooKeeper ensemble. It monitors these nodes to ensure their existence and manage their lifecycle collectively.

This class uses Apache Curator's PathChildrenCache recipe under the hood to track all znodes under the specified node's parent. See NodeAnnouncer for an announcer that uses the NodeCache recipe instead.

Constructor Summary

Constructors

Constructor	Description
PathChildrenAnnouncer(org.apache.curator.framework.CuratorFramework curator, ExecutorService exec)

Method Summary

Modifier and Type	Method	Description
void	announce(String path, byte[] bytes)	Overload of announce(String, byte[], boolean), but removes parent node of path after announcement.
void	announce(String path, byte[] bytes, boolean removeParentIfCreated)	Announces the provided bytes at the given path.
void	start()
void	stop()
void	unannounce(String path)	Unannounces an announcement created at path.
void	update(String path, byte[] bytes)

Methods inherited from class java.lang.Object

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

Constructor Details

PathChildrenAnnouncer

public PathChildrenAnnouncer(org.apache.curator.framework.CuratorFramework curator,
 ExecutorService exec)

Method Details

start

public void start()

Specified by:

start in interface ServiceAnnouncer

stop

public void stop()

Specified by:

stop in interface ServiceAnnouncer

announce

public void announce(String path,
 byte[] bytes)

Overload of announce(String, byte[], boolean), but removes parent node of path after announcement.

Specified by:

announce in interface ServiceAnnouncer

announce

public void announce(String path,
 byte[] bytes,
 boolean removeParentIfCreated)

Announces the provided bytes at the given path.

Announcement using PathChildrenAnnouncer will create an ephemeral znode at the specified path, and uses its parent path to watch all the siblings and children znodes of your specified path. The watched nodes will always exist until it is unannounced, or until stop() is called.

Specified by:

announce in interface ServiceAnnouncer

Parameters:

path - The path to announce at

bytes - The payload to announce

removeParentIfCreated - remove parent of "path" if we had created that parent during announcement

update

public void update(String path,
 byte[] bytes)

Specified by:

update in interface ServiceAnnouncer

unannounce

public void unannounce(String path)

Unannounces an announcement created at path. Note that if all announcements get removed, the Announcer will continue to have ZK watches on paths because clearing them out is a source of ugly race conditions.

If you need to completely clear all the state of what is being watched and announced, stop() the Announcer.

Specified by:

unannounce in interface ServiceAnnouncer

Parameters:

path - the path to unannounce