org.apache.zookeeper.server.watch

Class WatchManagerOptimized

java.lang.Object

org.apache.zookeeper.server.watch.WatchManagerOptimized

All Implemented Interfaces:

IDeadWatcherListener, IWatchManager

public class WatchManagerOptimized
extends Object
implements IWatchManager, IDeadWatcherListener

Optimized in memory and time complexity, compared to WatchManager, both the memory consumption and time complexity improved a lot, but it cannot efficiently remove the watcher when the session or socket is closed, for majority use case this is not a problem. Changed made compared to WatchManager: - Use HashSet and BitSet to store the watchers to find a balance between memory usage and time complexity - Use ReadWriteLock instead of synchronized to reduce lock retention - Lazily clean up the closed watchers

Constructor Summary

Constructors

Constructor and Description
WatchManagerOptimized()

Method Summary

Modifier and Type	Method and Description
boolean	addWatch(String path, Watcher watcher) Add watch to specific path.
boolean	containsWatcher(String path, Watcher watcher) Used in the OpCode.checkWatches, which is a read operation, since read and write requests are exclusively processed, we don't need to hold lock here.
void	dumpWatches(PrintWriter pwriter, boolean byPath) String representation of watches.
Map<Watcher,Set<String>>	getWatcher2PathesMap() May cause OOM if there are lots of watches, might better to forbid it in this class.
WatchesReport	getWatches() Returns a watch report.
WatchesPathReport	getWatchesByPath() Iterate through ConcurrentHashMap is 'safe', it will reflect the state of the map at the time iteration began, may miss update while iterating, given this is used in the commands to get a general idea of the watches state, we don't care about missing some update.
WatchesSummary	getWatchesSummary() Returns a watch summary.
void	processDeadWatchers(Set<Integer> deadWatchers) Entry for WatcherCleaner to remove dead watchers
boolean	removeWatcher(String path, Watcher watcher) Removes the specified watcher for the given path.
void	removeWatcher(Watcher watcher) The entry to remove the watcher when the cnxn is closed.
void	shutdown() Clean up the watch manager.
int	size() Get the size of watchers.
String	toString()
WatcherOrBitSet	triggerWatch(String path, Watcher.Event.EventType type) Distribute the watch event for the given path.
WatcherOrBitSet	triggerWatch(String path, Watcher.Event.EventType type, WatcherOrBitSet suppress) Distribute the watch event for the given path, but ignore those suppressed ones.

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.apache.zookeeper.server.watch.IWatchManager

addWatch, getRecursiveWatchQty

Constructor Detail

WatchManagerOptimized

public WatchManagerOptimized()

Method Detail

addWatch

public boolean addWatch(String path,
                        Watcher watcher)

Description copied from interface: IWatchManager

Add watch to specific path.

Specified by:

addWatch in interface IWatchManager

Parameters:

path - znode path

watcher - watcher object reference

Returns:

true if the watcher added is not already present

containsWatcher

public boolean containsWatcher(String path,
                               Watcher watcher)

Used in the OpCode.checkWatches, which is a read operation, since read and write requests are exclusively processed, we don't need to hold lock here. Different from addWatch this method doesn't mutate any state, so we don't need to hold read lock to avoid dead watcher (cnxn closed) being added to the watcher manager. It's possible that before we lazily clean up the dead watcher, this will return true, but since the cnxn is closed, the response will dropped as well, so it doesn't matter.

Specified by:

containsWatcher in interface IWatchManager

Parameters:

path - znode path

watcher - watcher object reference

Returns:

true if the watcher exists, false otherwise

removeWatcher

public boolean removeWatcher(String path,
                             Watcher watcher)

Description copied from interface: IWatchManager

Removes the specified watcher for the given path.

Specified by:

removeWatcher in interface IWatchManager

Parameters:

path - znode path

watcher - watcher object reference

Returns:

true if the watcher successfully removed, false otherwise

removeWatcher

public void removeWatcher(Watcher watcher)

Description copied from interface: IWatchManager

The entry to remove the watcher when the cnxn is closed.

Specified by:

removeWatcher in interface IWatchManager

Parameters:

watcher - watcher object reference

processDeadWatchers

public void processDeadWatchers(Set<Integer> deadWatchers)

Entry for WatcherCleaner to remove dead watchers

Specified by:

processDeadWatchers in interface IDeadWatcherListener

Parameters:

deadWatchers - the watchers need to be removed

triggerWatch

public WatcherOrBitSet triggerWatch(String path,
                                    Watcher.Event.EventType type)

Description copied from interface: IWatchManager

Distribute the watch event for the given path.

Specified by:

triggerWatch in interface IWatchManager

Parameters:

path - znode path

type - the watch event type

Returns:

the watchers have been notified

triggerWatch

public WatcherOrBitSet triggerWatch(String path,
                                    Watcher.Event.EventType type,
                                    WatcherOrBitSet suppress)

Description copied from interface: IWatchManager

Distribute the watch event for the given path, but ignore those suppressed ones.

Specified by:

triggerWatch in interface IWatchManager

Parameters:

path - znode path

type - the watch event type

suppress - the suppressed watcher set

Returns:

the watchers have been notified

size

public int size()

Description copied from interface: IWatchManager

Get the size of watchers.

Specified by:

size in interface IWatchManager

Returns:

the watchers number managed in this class.

shutdown

public void shutdown()

Description copied from interface: IWatchManager

Clean up the watch manager.

Specified by:

shutdown in interface IWatchManager

getWatchesSummary

public WatchesSummary getWatchesSummary()

Description copied from interface: IWatchManager

Returns a watch summary.

Specified by:

getWatchesSummary in interface IWatchManager

Returns:

watch summary

See Also:

WatchesSummary

getWatches

public WatchesReport getWatches()

Description copied from interface: IWatchManager

Returns a watch report.

Specified by:

getWatches in interface IWatchManager

Returns:

watch report

See Also:

WatchesReport

getWatchesByPath

public WatchesPathReport getWatchesByPath()

Iterate through ConcurrentHashMap is 'safe', it will reflect the state of the map at the time iteration began, may miss update while iterating, given this is used in the commands to get a general idea of the watches state, we don't care about missing some update.

Specified by:

getWatchesByPath in interface IWatchManager

Returns:

watch report

See Also:

WatchesPathReport

getWatcher2PathesMap

public Map<Watcher,Set<String>> getWatcher2PathesMap()

May cause OOM if there are lots of watches, might better to forbid it in this class.

dumpWatches

public void dumpWatches(PrintWriter pwriter,
                        boolean byPath)

Description copied from interface: IWatchManager

String representation of watches. Warning, may be large!

Specified by:

dumpWatches in interface IWatchManager

Parameters:

pwriter - the writer to dump the watches

byPath - iff true output watches by paths, otw output watches by connection

toString

public String toString()

Overrides:

toString in class Object