Package org.apache.curator.framework.recipes.atomic

Class DistributedAtomicInteger

java.lang.Object

org.apache.curator.framework.recipes.atomic.DistributedAtomicInteger

All Implemented Interfaces:

DistributedAtomicNumber<Integer>

public class DistributedAtomicInteger
extends Object
implements DistributedAtomicNumber<Integer>

A counter that attempts atomic increments. It first tries uses optimistic locking. If that fails, an optional InterProcessMutex is taken. For both optimistic and mutex, a retry policy is used to retry the increment.

The various increment methods return an AtomicValue object. You must always check AtomicValue.succeeded(). None of the methods (other than get()) are guaranteed to succeed.

Constructor Summary

Constructors

Constructor	Description
DistributedAtomicInteger(CuratorFramework client, String counterPath, RetryPolicy retryPolicy)	Creates in optimistic mode only - i.e.
DistributedAtomicInteger(CuratorFramework client, String counterPath, RetryPolicy retryPolicy, PromotedToLock promotedToLock)	Creates in mutex promotion mode.

Method Summary

Modifier and Type	Method	Description
AtomicValue<Integer>	add(Integer delta)	Add delta to the current value and return the new value information.
AtomicValue<Integer>	compareAndSet(Integer expectedValue, Integer newValue)	Atomically sets the value to the given updated value if the current value == the expected value.
AtomicValue<Integer>	decrement()	Subtract 1 from the current value and return the new value information.
void	forceSet(Integer newValue)	Forcibly sets the value of the counter without any guarantees of atomicity.
AtomicValue<Integer>	get()	Returns the current value of the counter.
AtomicValue<Integer>	increment()	Add 1 to the current value and return the new value information.
boolean	initialize(Integer initialize)	Atomic values are initially set to the equivalent of NULL in a database.
AtomicValue<Integer>	subtract(Integer delta)	Subtract delta from the current value and return the new value information.
AtomicValue<Integer>	trySet(Integer newValue)	Attempt to atomically set the value to the given value.

Methods inherited from class java.lang.Object

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

Constructor Details

DistributedAtomicInteger

public DistributedAtomicInteger(CuratorFramework client,
 String counterPath,
 RetryPolicy retryPolicy)

Creates in optimistic mode only - i.e. the promotion to a mutex is not done

Parameters:

client - the client

counterPath - path to hold the value

retryPolicy - the retry policy to use

DistributedAtomicInteger

public DistributedAtomicInteger(CuratorFramework client,
 String counterPath,
 RetryPolicy retryPolicy,
 PromotedToLock promotedToLock)

Creates in mutex promotion mode. The optimistic lock will be tried first using the given retry policy. If the increment does not succeed, a InterProcessMutex will be tried with its own retry policy

Parameters:

client - the client

counterPath - path to hold the value

retryPolicy - the retry policy to use

promotedToLock - the arguments for the mutex promotion

Method Details

get

public AtomicValue<Integer> get()
                         throws Exception

Description copied from interface: DistributedAtomicNumber

Returns the current value of the counter. NOTE: if the value has never been set, 0 is returned.

Specified by:

get in interface DistributedAtomicNumber<Integer>

Returns:

value info

Throws:

Exception - ZooKeeper errors

forceSet

public void forceSet(Integer newValue)
              throws Exception

Description copied from interface: DistributedAtomicNumber

Forcibly sets the value of the counter without any guarantees of atomicity.

Specified by:

forceSet in interface DistributedAtomicNumber<Integer>

Parameters:

newValue - the new value

Throws:

Exception - ZooKeeper errors

compareAndSet

public AtomicValue<Integer> compareAndSet(Integer expectedValue,
 Integer newValue)
                                   throws Exception

Description copied from interface: DistributedAtomicNumber

Atomically sets the value to the given updated value if the current value == the expected value. Remember to always check AtomicValue.succeeded().

Specified by:

compareAndSet in interface DistributedAtomicNumber<Integer>

Parameters:

expectedValue - the expected value

newValue - the new value for the counter

Returns:

value info

Throws:

Exception - ZooKeeper errors

trySet

public AtomicValue<Integer> trySet(Integer newValue)
                            throws Exception

Description copied from interface: DistributedAtomicNumber

Attempt to atomically set the value to the given value. Remember to always check AtomicValue.succeeded().

Specified by:

trySet in interface DistributedAtomicNumber<Integer>

Parameters:

newValue - the value to set

Returns:

value info

Throws:

Exception - ZooKeeper errors

initialize

public boolean initialize(Integer initialize)
                   throws Exception

Description copied from interface: DistributedAtomicNumber

Atomic values are initially set to the equivalent of NULL in a database. Use this method to initialize the value. The value will be set if and only iff the node does not exist.

Specified by:

initialize in interface DistributedAtomicNumber<Integer>

Parameters:

initialize - the initial value to set

Returns:

true if the value was set, false if the node already existed

Throws:

Exception - ZooKeeper errors

increment

public AtomicValue<Integer> increment()
                               throws Exception

Add 1 to the current value and return the new value information. Remember to always check AtomicValue.succeeded().

Specified by:

increment in interface DistributedAtomicNumber<Integer>

Returns:

value info

Throws:

Exception - ZooKeeper errors

decrement

public AtomicValue<Integer> decrement()
                               throws Exception

Subtract 1 from the current value and return the new value information. Remember to always check AtomicValue.succeeded().

Specified by:

decrement in interface DistributedAtomicNumber<Integer>

Returns:

value info

Throws:

Exception - ZooKeeper errors

add

public AtomicValue<Integer> add(Integer delta)
                         throws Exception

Add delta to the current value and return the new value information. Remember to always check AtomicValue.succeeded().

Specified by:

add in interface DistributedAtomicNumber<Integer>

Parameters:

delta - amount to add

Returns:

value info

Throws:

Exception - ZooKeeper errors

subtract

public AtomicValue<Integer> subtract(Integer delta)
                              throws Exception

Subtract delta from the current value and return the new value information. Remember to always check AtomicValue.succeeded().

Specified by:

subtract in interface DistributedAtomicNumber<Integer>

Parameters:

delta - amount to subtract

Returns:

value info

Throws:

Exception - ZooKeeper errors