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/*
* Copyright 2012-2021 Aerospike, Inc.
*
* Portions may be licensed to Aerospike, Inc. under one or more contributor
* license agreements WHICH ARE COMPATIBLE WITH THE APACHE LICENSE, VERSION 2.0.
*
* 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 com.aerospike.client.async;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.ReentrantLock;
/**
* Limit the number of commands allowed at any point in time.
*/
public final class Throttle {
private final ReentrantLock lock;
private final Condition avail;
private int available;
/**
* Construct throttle with max number of commands.
*/
public Throttle(int capacity) {
lock = new ReentrantLock(false);
avail = lock.newCondition();
available = capacity;
}
/**
* Wait for command slot(s).
*
* @param count count of commands to reserve
* @return if command should be processed
*/
public boolean waitForSlot(int count) {
try {
final ReentrantLock lock = this.lock;
lock.lockInterruptibly();
try {
while (available < count) {
avail.await();
}
available -= count;
return true;
}
finally {
lock.unlock();
}
}
catch (InterruptedException ie) {
return false;
}
}
/**
* Recover slot(s) from commands that have completed.
*
* @param count count of commands to reclaim
*/
public void addSlot(int count) {
lock.lock();
try {
available += count;
avail.signal();
}
finally {
lock.unlock();
}
}
/**
* Get current number of commands that could be run.
*/
public int getAvailable() {
return available;
}
}