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/*
* ============LICENSE_START=======================================================
* Common Utils-Test
* ================================================================================
* Copyright (C) 2018 AT&T Intellectual Property. All rights reserved.
* ================================================================================
* 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.
* ============LICENSE_END=========================================================
*/
package org.onap.policy.common.utils.time;
import java.util.Date;
import java.util.PriorityQueue;
import java.util.concurrent.CountDownLatch;
/**
* "Current" time, when running junit tests in multiple threads. This is intended to be
* injected into classes under test, to replace their {@link CurrentTime} objects. The
* {@link #sleep(long)} method blocks until all threads enter and then it moves the notion
* of "current" time forward, allowing threads to resume, as the end of their sleep time
* is reached. Additional threads do not resume until all threads have once again entered
* {@link #sleep(long)} or when {@link #threadCompleted()} is invoked to indicate that a
* thread will not re-enter {@link #sleep(long)}.
*/
public class TestTimeMulti extends CurrentTime {
/**
* Number of threads that will be sleeping simultaneously.
*/
private int nthreads;
/**
* "Current" time, in milliseconds, used by tests.
*/
private long tcur = System.currentTimeMillis();
/**
* Queue of sleeping threads waiting to be awakened.
*/
private final PriorityQueue<Info> queue = new PriorityQueue<>();
/**
* Used to synchronize updates.
*/
private final Object locker = new Object();
/**
* Constructor.
*
* @param nthreads number of threads that will be sleeping simultaneously
*/
public TestTimeMulti(int nthreads) {
this.nthreads = nthreads;
}
@Override
public long getMillis() {
return tcur;
}
@Override
public Date getDate() {
return new Date(tcur);
}
@Override
public void sleep(long sleepMs) throws InterruptedException {
if (sleepMs <= 0) {
return;
}
Info info = new Info(tcur + sleepMs);
synchronized (locker) {
queue.add(info);
if (queue.size() == nthreads) {
// all threads are now sleeping - wake one up
wakeThreads();
}
}
// this MUST happen outside of the "synchronized" block
info.await();
}
/**
* Indicates that a thread has terminated or that it will no longer be invoking
* {@link #sleep(long)}. Awakens the next sleeping thread, if the queue is full after
* removing the terminated thread.
*
* @throws IllegalStateException if the queue is already full
*/
public void threadCompleted() {
synchronized (locker) {
int sz = queue.size();
if (sz >= nthreads) {
throw new IllegalStateException("too many threads still sleeping");
}
--nthreads;
if (sz == nthreads) {
// after removing terminated thread - queue is now full; awaken something
wakeThreads();
}
}
}
/**
* Advances the "current" time and awakens any threads sleeping until that time.
*/
private void wakeThreads() {
Info info = queue.poll();
if (info == null) {
return;
}
tcur = info.getAwakenAtMs();
info.wake();
while ((info = queue.poll()) != null) {
if (tcur == info.getAwakenAtMs()) {
info.wake();
} else {
// not ready to wake this thread - put it back in the queue
queue.add(info);
break;
}
}
}
/**
* Info about a sleeping thread.
*/
private static class Info implements Comparable<Info> {
/**
* Time, in milliseconds, at which the associated thread should awaken.
*/
private final long awakenAtMs;
/**
* This is triggered when the associated thread should awaken.
*/
private final CountDownLatch latch = new CountDownLatch(1);
/**
* Constructor.
*
* @param awakenAtMs time, in milliseconds, at which the associated thread should
* awaken
*/
public Info(long awakenAtMs) {
this.awakenAtMs = awakenAtMs;
}
public long getAwakenAtMs() {
return awakenAtMs;
}
/**
* Awakens the associated thread by decrementing its latch.
*/
public void wake() {
latch.countDown();
}
/**
* Blocks the current thread until awakened (i.e., until its latch is
* decremented).
*
* @throws InterruptedException can be interrupted
*/
public void await() throws InterruptedException {
latch.await();
}
@Override
public int compareTo(Info object) {
int diff = Long.compare(awakenAtMs, object.awakenAtMs);
// this assumes that Object.toString() is unique for each Info object
if (diff == 0) {
diff = this.toString().compareTo(object.toString());
}
return diff;
}
}
}
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