Interface IgniteSemaphore
-
- All Superinterfaces:
AutoCloseable,Closeable
public interface IgniteSemaphore extends Closeable
This interface provides a rich API for working with distributed semaphore.Functionality
Distributed semaphore provides functionality similar tojava.util.concurrent.Semaphore.Creating Distributed Semaphore
Instance of cache semaphore can be created by calling the following method:Ignite.semaphore(String, int, boolean, boolean).
-
-
Method Summary
All Methods Instance Methods Abstract Methods Modifier and Type Method Description voidacquire()Acquires a permit from this semaphore, blocking until one is available, or the thread is interrupted.voidacquire(int permits)Acquires the given number of permits from this semaphore, blocking until all are available, or the thread is interrupted.<T> IgniteFuture<T>acquireAndExecute(IgniteCallable<T> callable, int numPermits)Acquires the given semaphore, executes the given callable and schedules the release of permits asynchronouslyvoidacquireUninterruptibly()Acquires a permit from this semaphore, blocking until one is available.voidacquireUninterruptibly(int permits)Acquires the given number of permits from this semaphore, blocking until all are available.intavailablePermits()Returns the current number of permits available in this semaphore.voidclose()Removes this semaphore.intdrainPermits()Acquires and returns all permits that are immediately available.intgetQueueLength()Returns an estimate of the number of nodes waiting to acquire.booleanhasQueuedThreads()Queries whether any threads are waiting to acquire.booleanisBroken()Getsbrokenstatus of the semaphore.booleanisFailoverSafe()Returnstrueif this semaphore is safe to use after node failure.Stringname()Gets name of the semaphore.voidrelease()Releases a permit, returning it to the semaphore.voidrelease(int permits)Releases the given number of permits, returning them to the semaphore.booleanremoved()Getsremovedstatus of the semaphore.booleantryAcquire()Acquires a permit from this semaphore, only if one is available at the time of invocation.booleantryAcquire(int permits)Acquires the given number of permits from this semaphore, only if all are available at the time of invocation.booleantryAcquire(int permits, long timeout, TimeUnit unit)Acquires the given number of permits from this semaphore, if all become available within the given waiting time and the current thread has not been interrupted.booleantryAcquire(long timeout, TimeUnit unit)Acquires a permit from this semaphore, if one becomes available within the given waiting time and the current thread has not been interrupted.
-
-
-
Method Detail
-
name
String name()
Gets name of the semaphore.- Returns:
- Name of the semaphore.
-
acquire
void acquire() throws IgniteInterruptedExceptionAcquires a permit from this semaphore, blocking until one is available, or the thread is interrupted.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 two things happens:
- Some other thread invokes the
release()method for this semaphore and the current thread is next to be assigned a permit; 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,
IgniteInterruptedExceptionis thrown and the current thread's interrupted status is cleared.- Throws:
IgniteInterruptedException- if the current thread is interrupted
- Some other thread invokes the
-
acquireUninterruptibly
void acquireUninterruptibly()
Acquires a permit from this semaphore, blocking until one is available.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 some other thread invokes the
release()method for this semaphore and the current thread is next to be assigned a permit.If the current thread is interrupted while waiting for a permit then it will continue to wait, but the time at which the thread is assigned a permit may change compared to the time it would have received the permit had no interruption occurred. When the thread does return from this method its interrupt status will be set.
-
tryAcquire
boolean tryAcquire()
Acquires a permit from this semaphore, only if one is available at the time of invocation.Acquires a permit, if one is available and returns immediately, with the value
true, reducing the number of available permits by one.If no permit is available then this method will return immediately with the value
false.- Returns:
trueif a permit was acquired andfalseotherwise
-
tryAcquire
boolean tryAcquire(long timeout, TimeUnit unit) throws IgniteInterruptedExceptionAcquires a permit from this semaphore, if one becomes available within the given waiting time and the current thread has not been interrupted.Acquires a permit, if one is available and returns immediately, with the value
true, 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 the
release()method for this semaphore and the current thread is next to be assigned a permit; or - Some other thread interrupts the current thread; or
- The specified waiting time elapses.
If a permit is acquired then the value
trueis returned.If the current thread:
- has its interrupted status set on entry to this method; or
- is interrupted while waiting to acquire a permit,
IgniteInterruptedExceptionis thrown and the current thread's interrupted status is cleared.If the specified waiting time elapses then the value
falseis returned. If the time is less than or equal to zero, the method will not wait at all.- Parameters:
timeout- the maximum time to wait for a permitunit- the time unit of thetimeoutargument- Returns:
trueif a permit was acquired andfalseif the waiting time elapsed before a permit was acquired- Throws:
IgniteInterruptedException- if the current thread is interrupted
- Some other thread invokes the
-
acquireUninterruptibly
void acquireUninterruptibly(int permits)
Acquires the given number of permits from this semaphore, blocking until all are available.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 some other thread invokes one of the
releasemethods for this semaphore, the current thread is next to be assigned permits and the number of available permits satisfies this request.If the current thread is interrupted while waiting for permits then it will continue to wait and its position in the queue is not affected. When the thread does return from this method its interrupt status will be set.
- Parameters:
permits- the number of permits to acquire- Throws:
IllegalArgumentException- ifpermitsis negative
-
availablePermits
int availablePermits()
Returns the current number of permits available in this semaphore.This method is typically used for debugging and testing purposes.
- Returns:
- the number of permits available in this semaphore
-
drainPermits
int drainPermits()
Acquires and returns all permits that are immediately available.- Returns:
- the number of permits acquired
-
release
void release()
Releases a permit, returning it to the semaphore.Releases a permit, increasing the number of available permits by one. If any threads are trying to acquire a permit, then one is selected and given the permit that was just released. That thread is (re)enabled for thread scheduling purposes.
There is no requirement that a thread that releases a permit must have acquired that permit by calling
acquire(). Correct usage of a semaphore is established by programming convention in the application.
-
tryAcquire
boolean tryAcquire(int permits, long timeout, TimeUnit unit) throws IgniteInterruptedExceptionAcquires the given number of permits from this semaphore, if all become available within the given waiting time and the current thread has not been interrupted.Acquires the given number of permits, if they are available and returns immediately, with the value
true, 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
releasemethods for this semaphore, 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.
If the permits are acquired then the value
trueis returned.If the current thread:
- has its interrupted status set on entry to this method; or
- is interrupted while waiting to acquire the permits,
IgniteInterruptedExceptionis thrown and the current thread's interrupted status is cleared. Any permits that were to be assigned to this thread, are instead assigned to other threads trying to acquire permits, as if the permits had been made available by a call torelease().If the specified waiting time elapses then the value
falseis returned. If the time is less than or equal to zero, the method will not wait at all. Any permits that were to be assigned to this thread, are instead assigned to other threads trying to acquire permits, as if the permits had been made available by a call torelease().- Parameters:
permits- the number of permits to acquiretimeout- the maximum time to wait for the permitsunit- the time unit of thetimeoutargument- Returns:
trueif all permits were acquired andfalseif the waiting time elapsed before all permits were acquired- Throws:
IgniteInterruptedException- if the current thread is interruptedIllegalArgumentException- ifpermitsis negative
- Some other thread invokes one of the
-
tryAcquire
boolean tryAcquire(int permits)
Acquires the given number of permits from this semaphore, only if all are available at the time of invocation.Acquires the given number of permits, if they are available, and returns immediately, with the value
true, reducing the number of available permits by the given amount.If insufficient permits are available then this method will return immediately with the value
falseand the number of available permits is unchanged.If you want to honor the failoverSafe setting, then use
tryAcquire(permits, 0, TimeUnit.SECONDS)which is almost equivalent (it also detects interruption).- Parameters:
permits- the number of permits to acquire- Returns:
trueif the permits were acquired andfalseotherwise- Throws:
IllegalArgumentException- ifpermitsis negative
-
acquire
void acquire(int permits) throws IgniteInterruptedExceptionAcquires the given number of permits from this semaphore, blocking until all are available, or the thread is interrupted.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 two things happens:
- Some other thread invokes one of the
releasemethods for this semaphore, 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.
If the current thread:
- has its interrupted status set on entry to this method; or
- is interrupted while waiting for a permit,
IgniteInterruptedExceptionis thrown and the current thread's interrupted status is cleared. Any permits that were to be assigned to this thread are instead assigned to other threads trying to acquire permits, as if permits had been made available by a call torelease().- Parameters:
permits- the number of permits to acquire- Throws:
IgniteInterruptedException- if the current thread is interruptedIllegalArgumentException- ifpermitsis negative
- Some other thread invokes one of the
-
acquireAndExecute
<T> IgniteFuture<T> acquireAndExecute(IgniteCallable<T> callable, int numPermits) throws Exception
Acquires the given semaphore, executes the given callable and schedules the release of permits asynchronously- Type Parameters:
T- Type of the callable execution result.- Parameters:
callable- the callable to executenumPermits- the number of permits to acquire- Returns:
- Callable execution future.
- Throws:
Exception- if the callable throws an exception
-
release
void release(int permits)
Releases the given number of permits, returning them to the semaphore.Releases the given number of permits, increasing the number of available permits by that amount. If any threads are trying to acquire permits, then one is selected and given the permits that were just released. If the number of available permits satisfies that thread's request then that thread is (re)enabled for thread scheduling purposes; otherwise the thread will wait until sufficient permits are available. If there are still permits available after this thread's request has been satisfied, then those permits are assigned in turn to other threads trying to acquire permits.
There is no requirement that a thread that releases a permit must have acquired that permit by calling
acquire. Correct usage of a semaphore is established by programming convention in the application.- Parameters:
permits- the number of permits to release- Throws:
IllegalArgumentException- ifpermitsis negative
-
isFailoverSafe
boolean isFailoverSafe()
Returnstrueif this semaphore is safe to use after node failure. If not, IgniteInterruptedException is thrown on every other node after node failure.- Returns:
trueif this semaphore has failoverSafe set true
-
hasQueuedThreads
boolean hasQueuedThreads()
Queries whether any threads are waiting to acquire. Note that because cancellations may occur at any time, atruereturn does not guarantee that any other thread will ever acquire. This method is designed primarily for use in monitoring of the system state.- Returns:
trueif there may be other threads waiting to acquire the lock
-
getQueueLength
int getQueueLength()
Returns an estimate of the number of nodes waiting to acquire. The value is only an estimate because the number of nodes that are waiting may change dynamically while this method traverses internal data structures. This method is designed for use in monitoring of the system state, not for synchronization control.- Returns:
- the estimated number of nodes waiting for this lock
-
isBroken
boolean isBroken()
Getsbrokenstatus of the semaphore.- Returns:
Trueif a node failed on this semaphore and failoverSafe flag was set to false,falseotherwise.
-
removed
boolean removed()
Getsremovedstatus of the semaphore.- Returns:
Trueif semaphore was removed from cache,falseotherwise.
-
close
void close()
Removes this semaphore.- Specified by:
closein interfaceAutoCloseable- Specified by:
closein interfaceCloseable- Throws:
IgniteException- If operation failed.
-
-