com.hazelcast.cp.internal.datastructures.semaphore.proxy

Class RaftSessionAwareSemaphoreProxy

java.lang.Object

com.hazelcast.cp.internal.session.SessionAwareProxy

com.hazelcast.cp.internal.datastructures.semaphore.proxy.RaftSessionAwareSemaphoreProxy

All Implemented Interfaces:

DistributedObject, ISemaphore

public class RaftSessionAwareSemaphoreProxy
extends SessionAwareProxy
implements ISemaphore

Server-side session-aware proxy of Raft-based ISemaphore

Field Summary

Fields

Modifier and Type	Field and Description
static int	DRAIN_SESSION_ACQ_COUNT Since a proxy does not know how many permits will be drained on the Raft group, it uses this constant to increment its local session acquire count.

Fields inherited from class com.hazelcast.cp.internal.session.SessionAwareProxy

groupId

Constructor Summary

Constructors

Constructor and Description
RaftSessionAwareSemaphoreProxy(NodeEngine nodeEngine, RaftGroupId groupId, String proxyName, String objectName)

Method Summary

Modifier and Type	Method and Description
void	acquire() Acquires a permit if one is available, and returns immediately, reducing the number of available permits by one.
void	acquire(int permits) Acquires the given number of permits if they are available, and returns immediately, reducing the number of available permits by the given amount.
int	availablePermits() Returns the current number of permits currently available in this semaphore.
void	destroy() Destroys this object cluster-wide.
int	drainPermits() Acquires and returns all permits that are available at invocation time.
String	getName() Returns the name of this ISemaphore instance.
String	getPartitionKey() Returns the key of the partition that this DistributedObject is assigned to.
String	getServiceName() Returns the service name for this object.
void	increasePermits(int increase) Increases the number of available permits by the indicated amount.
boolean	init(int permits) Tries to initialize this ISemaphore instance with the given permit count
void	reducePermits(int reduction) Reduces the number of available permits by the indicated amount.
void	release() Releases a permit and increases the number of available permits by one.
void	release(int permits) Releases the given number of permits and increases the number of available permits by that amount.
boolean	tryAcquire() Acquires a permit if one is available, and returns true immediately.
boolean	tryAcquire(int permits) Acquires the given number of permits if they are available, and returns true immediately.
boolean	tryAcquire(int permits, long timeout, TimeUnit unit) Acquires the given number of permits and returns true, if they become available during the given waiting time.
boolean	tryAcquire(long timeout, TimeUnit unit) Acquires a permit and returns true, if one becomes available during the given waiting time and the current thread has not been interrupted.

Methods inherited from class com.hazelcast.cp.internal.session.SessionAwareProxy

acquireSession, acquireSession, getGroupId, getOrCreateUniqueThreadId, getSession, invalidateSession, releaseSession, releaseSession

Methods inherited from class java.lang.Object

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

Field Detail

DRAIN_SESSION_ACQ_COUNT

public static final int DRAIN_SESSION_ACQ_COUNT

Since a proxy does not know how many permits will be drained on the Raft group, it uses this constant to increment its local session acquire count. Then, it adjusts the local session acquire count after the drain response is returned.

See Also:

Constant Field Values

Constructor Detail

RaftSessionAwareSemaphoreProxy

public RaftSessionAwareSemaphoreProxy(NodeEngine nodeEngine,
                                      RaftGroupId groupId,
                                      String proxyName,
                                      String objectName)

Method Detail

init

public boolean init(int permits)

Description copied from interface: ISemaphore

Tries to initialize this ISemaphore instance with the given permit count

Specified by:

init in interface ISemaphore

Parameters:

permits - the given permit count

Returns:

true if initialization success. false if already initialized

acquire

public void acquire()

Description copied from interface: ISemaphore

Acquires a permit if one is available, and returns immediately, reducing the number of available permits by one.

If no permit is available, then the current thread becomes disabled for thread scheduling purposes and lies dormant until one of three things happens:

• some other thread invokes one of the ISemaphore.release() methods for this semaphore and the current thread is next to be assigned a permit,
• this ISemaphore instance is destroyed, or
• some other thread interrupts the current thread.

If the current thread:

• has its interrupted status set on entry to this method; or
• is interrupted while waiting for a permit,

then InterruptedException is thrown and the current thread's interrupted status is cleared.

Specified by:

acquire in interface ISemaphore

acquire

public void acquire(int permits)

Description copied from interface: ISemaphore

Acquires the given number of permits if they are available, and returns immediately, reducing the number of available permits by the given amount.

If insufficient permits are available then the current thread becomes disabled for thread scheduling purposes and lies dormant until one of three things happens:

• some other thread invokes one of the release methods for this semaphore, the current thread is next to be assigned permits and the number of available permits satisfies this request,
• or this ISemaphore instance is destroyed,
• or some other thread interrupts the current thread.

If the current thread:

• has its interrupted status set on entry to this method, or
• is interrupted while waiting for a permit,

then InterruptedException is thrown and the current thread's interrupted status is cleared.

Specified by:

acquire in interface ISemaphore

Parameters:

permits - the number of permits to acquire

tryAcquire

public boolean tryAcquire()

Description copied from interface: ISemaphore

Acquires a permit if one is available, and returns true immediately. If no permit is available, returns false immediately.

Specified by:

tryAcquire in interface ISemaphore

Returns:

true if a permit was acquired, false otherwise

tryAcquire

public boolean tryAcquire(int permits)

Description copied from interface: ISemaphore

Acquires the given number of permits if they are available, and returns true immediately. If the requested number of permits are not available, returns false immediately.

Specified by:

tryAcquire in interface ISemaphore

Parameters:

permits - the number of permits to acquire

Returns:

true if the permits were acquired, false otherwise

tryAcquire

public boolean tryAcquire(long timeout,
                          TimeUnit unit)

Description copied from interface: ISemaphore

Acquires a permit and returns true, if one becomes available during the given waiting time and the current thread has not been interrupted. If a permit is acquired, the number of available permits in the ISemaphore instance is also reduced by one.

If no permit is available, then the current thread becomes disabled for thread scheduling purposes and lies dormant until one of three things happens:

• some other thread releases a permit and the current thread is next to be assigned a permit,
• or this ISemaphore instance is destroyed,
• or some other thread interrupts the current thread,
• or the specified waiting time elapses.

Returns true if a permit is successfully acquired.

Returns false if the specified waiting time elapses without acquiring a permit. If the time is less than or equal to zero, the method will not wait at all.

If the current thread:

• has its interrupted status set on entry to this method,
• or is interrupted while waiting for a permit,

then InterruptedException is thrown and the current thread's interrupted status is cleared.

Specified by:

tryAcquire in interface ISemaphore

Parameters:

timeout - the maximum time to wait for a permit

unit - the time unit of the timeout argument

Returns:

true if a permit was acquired and false if the waiting time elapsed before a permit was acquired

tryAcquire

public boolean tryAcquire(int permits,
                          long timeout,
                          TimeUnit unit)

Description copied from interface: ISemaphore

Acquires the given number of permits and returns true, if they become available during the given waiting time. If permits are acquired, the number of available permits in the ISemaphore instance is also reduced by the given amount.

If no sufficient permits are available, then the current thread becomes disabled for thread scheduling purposes and lies dormant until one of three things happens:

• permits are released by other threads, the current thread is next to be assigned permits and the number of available permits satisfies this request,
• or some other thread interrupts the current thread,
• or the specified waiting time elapses.

Returns true if requested permits are successfully acquired.

Returns false if the specified waiting time elapses without acquiring permits. If the time is less than or equal to zero, the method will not wait at all.

If the current thread:

• has its interrupted status set on entry to this method,
• or is interrupted while waiting for a permit,

then InterruptedException is thrown and the current thread's interrupted status is cleared.

Specified by:

tryAcquire in interface ISemaphore

Parameters:

permits - the number of permits to acquire

timeout - the maximum time to wait for the permits

unit - the time unit of the timeout argument

Returns:

true if all permits were acquired, false if the waiting time elapsed before all permits could be acquired

release

public void release()

Description copied from interface: ISemaphore

Releases a permit and increases the number of available permits by one. If some threads in the cluster are blocked for acquiring a permit, one of them will unblock by acquiring the permit released by this call.

If the underlying ISemaphore impl is the non-JDK compatible CP impl that is configured via CPSemaphoreConfig and fetched via CPSubsystem, then a HazelcastInstance can only release a permit which it has acquired before. In other words, a HazelcastInstance cannot release a permit without acquiring it first.

Otherwise, which means the underlying impl is either the JDK compatible CP impl configured via CPSemaphoreConfig and fetched via CPSubsystem, or it is the old impl fetched via HazelcastInstance.getSemaphore(String), there is no requirement that a HazelcastInstance that releases a permit must have acquired that permit by calling one of the ISemaphore.acquire() methods. A HazelcastInstance can freely release a permit without acquiring it first. In this case, correct usage of a semaphore is established by programming convention in the application.

Specified by:

release in interface ISemaphore

release

public void release(int permits)

Description copied from interface: ISemaphore

Releases the given number of permits and increases the number of available permits by that amount. If some threads in the cluster are blocked for acquiring permits, they will be notified.

If the underlying ISemaphore impl is the non-JDK compatible CP impl that is configured via CPSemaphoreConfig and fetched via CPSubsystem, then a HazelcastInstance can only release a permit which it has acquired before. In other words, a HazelcastInstance cannot release a permit without acquiring it first.

Otherwise, which means the underlying impl is either the JDK compatible CP impl configured via CPSemaphoreConfig and fetched via CPSubsystem, or it is the old impl fetched via HazelcastInstance.getSemaphore(String), there is no requirement that a HazelcastInstance that releases a permit must have acquired that permit by calling one of the ISemaphore.acquire() methods. A HazelcastInstance can freely release a permit without acquiring it first. In this case, correct usage of a semaphore is established by programming convention in the application.

Specified by:

release in interface ISemaphore

Parameters:

permits - the number of permits to release

availablePermits

public int availablePermits()

Description copied from interface: ISemaphore

Returns the current number of permits currently available in this semaphore.

This method is typically used for debugging and testing purposes.

Specified by:

availablePermits in interface ISemaphore

Returns:

the number of permits available in this semaphore

drainPermits

public int drainPermits()

Description copied from interface: ISemaphore

Acquires and returns all permits that are available at invocation time.

Specified by:

drainPermits in interface ISemaphore

Returns:

the number of permits drained

reducePermits

public void reducePermits(int reduction)

Description copied from interface: ISemaphore

Reduces the number of available permits by the indicated amount. This method differs from acquire as it does not block until permits become available. Similarly, if the caller has acquired some permits, they are not released with this call.

Specified by:

reducePermits in interface ISemaphore

Parameters:

reduction - the number of permits to reduce

increasePermits

public void increasePermits(int increase)

Description copied from interface: ISemaphore

Increases the number of available permits by the indicated amount. If there are some threads waiting for permits to become available, they will be notified. Moreover, if the caller has acquired some permits, they are not released with this call.

Specified by:

increasePermits in interface ISemaphore

Parameters:

increase - the number of permits to increase

getName

public String getName()

Description copied from interface: ISemaphore

Returns the name of this ISemaphore instance.

Specified by:

getName in interface DistributedObject

Specified by:

getName in interface ISemaphore

Returns:

name of this instance

getPartitionKey

public String getPartitionKey()

Description copied from interface: DistributedObject

Returns the key of the partition that this DistributedObject is assigned to. The returned value only has meaning for a non-partitioned data structure like an IAtomicLong. For a partitioned data structure like an IMap, the returned value will not be null, but otherwise undefined.

Specified by:

getPartitionKey in interface DistributedObject

Returns:

the partition key.

getServiceName

public String getServiceName()

Description copied from interface: DistributedObject

Returns the service name for this object.

Specified by:

getServiceName in interface DistributedObject

Returns:

the service name for this object.

destroy

public void destroy()

Description copied from interface: DistributedObject

Destroys this object cluster-wide. Clears and releases all resources for this object.

Specified by:

destroy in interface DistributedObject