org.redisson.api.RSemaphore Maven / Gradle / Ivy
/**
* Copyright 2018 Nikita Koksharov
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.redisson.api;
import java.util.concurrent.TimeUnit;
/**
* Distributed and concurrent implementation of {@link java.util.concurrent.Semaphore}.
*
* Works in non-fair mode. Therefore order of acquiring is unpredictable.
*
* @author Nikita Koksharov
*
*/
public interface RSemaphore extends RExpirable, RSemaphoreAsync {
/**
* Acquires a permit from this semaphore, blocking until one is
* available, or the thread is {@linkplain Thread#interrupt 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 {@link #release} method for this
* semaphore and the current thread is next to be assigned a permit; or
*
- Some other thread {@linkplain Thread#interrupt interrupts}
* the current thread.
*
*
* @throws InterruptedException if the current thread is interrupted
*/
void acquire() throws InterruptedException;
/**
* Acquires the given number of permits from this semaphore,
* blocking until all are available,
* or the thread is {@linkplain Thread#interrupt 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 {@link #release() release}
* methods 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 {@linkplain Thread#interrupt interrupts}
* the current thread.
*
*
* @param permits the number of permits to acquire
* @throws InterruptedException if the current thread is interrupted
* @throws IllegalArgumentException if {@code permits} is negative
*/
void acquire(int permits) throws InterruptedException;
/**
* Acquires a permit only if one is available at the
* time of invocation.
*
* Acquires a permit, if one is available and returns immediately,
* with the value {@code true},
* reducing the number of available permits by one.
*
*
If no permit is available then this method will return
* immediately with the value {@code false}.
*
* @return {@code true} if a permit was acquired and {@code false}
* otherwise
*/
boolean tryAcquire();
/**
* Acquires the given number of permits only if all are available at the
* time of invocation.
*
*
Acquires a permits, if all are available and returns immediately,
* with the value {@code true},
* reducing the number of available permits by given number of permits.
*
*
If no permits are available then this method will return
* immediately with the value {@code false}.
*
* @param permits the number of permits to acquire
* @return {@code true} if a permit was acquired and {@code false}
* otherwise
*/
boolean tryAcquire(int permits);
/**
* Acquires a permit from this semaphore, if one becomes available
* within the given waiting time and the current thread has not
* been {@linkplain Thread#interrupt interrupted}.
*
*
Acquires a permit, if one is available and returns immediately,
* with the value {@code 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 {@link #release} method for this
* semaphore and the current thread is next to be assigned a permit; or
*
- Some other thread {@linkplain Thread#interrupt interrupts}
* the current thread; or
*
- The specified waiting time elapses.
*
*
* If a permit is acquired then the value {@code true} is returned.
*
*
If the specified waiting time elapses then the value {@code false}
* is returned. If the time is less than or equal to zero, the method
* will not wait at all.
*
* @param waitTime the maximum time to wait for a permit
* @param unit the time unit of the {@code timeout} argument
* @return {@code true} if a permit was acquired and {@code false}
* if the waiting time elapsed before a permit was acquired
* @throws InterruptedException if the current thread is interrupted
*/
boolean tryAcquire(long waitTime, TimeUnit unit) throws InterruptedException;
/**
* Acquires the given number of permits only if all are available
* within the given waiting time and the current thread has not
* been {@linkplain Thread#interrupt interrupted}.
*
*
Acquires a permits, if all are available and returns immediately,
* with the value {@code 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 {@link #release} method for this
* semaphore and the current thread is next to be assigned a permit; or
*
- Some other thread {@linkplain Thread#interrupt interrupts}
* the current thread; or
*
- The specified waiting time elapses.
*
*
* If a permits is acquired then the value {@code true} is returned.
*
*
If the specified waiting time elapses then the value {@code false}
* is returned. If the time is less than or equal to zero, the method
* will not wait at all.
*
* @param permits amount
* @param waitTime the maximum time to wait for a permit
* @param unit the time unit of the {@code timeout} argument
* @return {@code true} if a permit was acquired and {@code false}
* if the waiting time elapsed before a permit was acquired
* @throws InterruptedException if the current thread is interrupted
*/
boolean tryAcquire(int permits, long waitTime, TimeUnit unit) throws InterruptedException;
/**
* Releases a permit, returning it to the semaphore.
*
*
Releases a permit, increasing the number of available permits by
* one. If any threads of Redisson client are trying to acquire a permit,
* then one is selected and given the permit that was just released.
*
*
There is no requirement that a thread that releases a permit must
* have acquired that permit by calling {@link #acquire}.
* Correct usage of a semaphore is established by programming convention
* in the application.
*/
void release();
/**
* Releases the given number of permits, returning them to the semaphore.
*
*
Releases the given number of permits, increasing the number of available permits by
* the given number of permits. If any threads of Redisson client are trying to
* acquire a permits, then next threads is selected and tries to acquire the permits that was just released.
*
*
There is no requirement that a thread that releases a permits must
* have acquired that permit by calling {@link #acquire}.
* Correct usage of a semaphore is established by programming convention
* in the application.
*
* @param permits amount
*/
void release(int permits);
/**
* Returns the current number of available permits.
*
* @return number of available permits
*/
int availablePermits();
/**
* Acquires and returns all permits that are immediately available.
*
* @return the number of permits acquired
*/
int drainPermits();
/**
* Sets number of permits.
*
* @param permits - number of permits
* @return true if permits has been set successfully, otherwise false.
*/
boolean trySetPermits(int permits);
/**
* Shrinks the number of available permits by the indicated
* reduction.
*
* @param permits - reduction the number of permits to remove
* @throws IllegalArgumentException if {@code reduction} is negative
*/
void reducePermits(int permits);
}