org.apache.curator.framework.recipes.shared

Class SharedCount

java.lang.Object

org.apache.curator.framework.recipes.shared.SharedCount

All Implemented Interfaces:

Closeable, AutoCloseable, org.apache.curator.framework.listen.Listenable<SharedCountListener>, SharedCountReader

public class SharedCount
extends Object
implements Closeable, SharedCountReader, org.apache.curator.framework.listen.Listenable<SharedCountListener>

Manages a shared integer. All clients watching the same path will have the up-to-date value of the shared integer (considering ZK's normal consistency guarantees).

Constructor Summary

Constructors

Constructor and Description
SharedCount(org.apache.curator.framework.CuratorFramework client, String path, int seedValue)

Method Summary

Modifier and Type	Method and Description
void	addListener(SharedCountListener listener)
void	addListener(SharedCountListener listener, Executor executor)
void	close()
int	getCount() Return the current value of the count
VersionedValue<Integer>	getVersionedValue() Return the current count and version
void	removeListener(SharedCountListener listener)
void	setCount(int newCount) Change the shared count value irrespective of its previous state
void	start() The shared count must be started before it can be used.
boolean	trySetCount(int newCount) Deprecated. use trySetCount(VersionedValue, int) for stronger atomicity guarantees. Even if this object's internal state is up-to-date, the caller has no way to ensure that they've read the most recently seen count.
boolean	trySetCount(VersionedValue<Integer> previous, int newCount) Changes the shared count only if its value has not changed since the version specified by newCount.

Methods inherited from class java.lang.Object

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

Constructor Detail

SharedCount

public SharedCount(org.apache.curator.framework.CuratorFramework client,
                   String path,
                   int seedValue)

Parameters:

client - the client

path - the shared path - i.e. where the shared count is stored

seedValue - the initial value for the count if/f the path has not yet been created

Method Detail

getCount

public int getCount()

Description copied from interface: SharedCountReader

Return the current value of the count

Specified by:

getCount in interface SharedCountReader

Returns:

count

getVersionedValue

public VersionedValue<Integer> getVersionedValue()

Description copied from interface: SharedCountReader

Return the current count and version

Specified by:

getVersionedValue in interface SharedCountReader

Returns:

count and version

setCount

public void setCount(int newCount)
              throws Exception

Change the shared count value irrespective of its previous state

Parameters:

newCount - new value

Throws:

Exception - ZK errors, interruptions, etc.

trySetCount

@Deprecated
public boolean trySetCount(int newCount)
                                throws Exception

Deprecated. use trySetCount(VersionedValue, int) for stronger atomicity guarantees. Even if this object's internal state is up-to-date, the caller has no way to ensure that they've read the most recently seen count.

Changes the shared count only if its value has not changed since this client last read it. If the count has changed, the value is not set and this client's view of the value is updated. i.e. if the count is not successful you can get the updated value by calling getCount().

Parameters:

newCount - the new value to attempt

Returns:

true if the change attempt was successful, false if not. If the change was not successful, getCount() will return the updated value

Throws:

Exception - ZK errors, interruptions, etc.

trySetCount

public boolean trySetCount(VersionedValue<Integer> previous,
                           int newCount)
                    throws Exception

Changes the shared count only if its value has not changed since the version specified by newCount. If the count has changed, the value is not set and this client's view of the value is updated. i.e. if the count is not successful you can get the updated value by calling getCount().

Parameters:

newCount - the new value to attempt

Returns:

true if the change attempt was successful, false if not. If the change was not successful, getCount() will return the updated value

Throws:

Exception - ZK errors, interruptions, etc.

addListener

public void addListener(SharedCountListener listener)

Specified by:

addListener in interface org.apache.curator.framework.listen.Listenable<SharedCountListener>

addListener

public void addListener(SharedCountListener listener,
                        Executor executor)

Specified by:

addListener in interface org.apache.curator.framework.listen.Listenable<SharedCountListener>

removeListener

public void removeListener(SharedCountListener listener)

Specified by:

removeListener in interface org.apache.curator.framework.listen.Listenable<SharedCountListener>

start

public void start()
           throws Exception

The shared count must be started before it can be used. Call close() when you are finished with the shared count

Throws:

Exception - ZK errors, interruptions, etc.

close

public void close()
           throws IOException

Specified by:

close in interface Closeable

Specified by:

close in interface AutoCloseable

Throws:

IOException