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/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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.apache.solr.util;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.Executor;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.RejectedExecutionException;
import java.util.concurrent.Semaphore;
import org.apache.solr.common.util.ExecutorUtil;
public class OrderedExecutor implements Executor {
private final ExecutorService delegate;
private final SparseStripedLock sparseStripedLock;
public OrderedExecutor(int numThreads, ExecutorService delegate) {
this.delegate = delegate;
this.sparseStripedLock = new SparseStripedLock<>(numThreads);
}
@Override
public void execute(Runnable runnable) {
execute(null, runnable);
}
/**
* Execute the given command in the future. If another command with same {@code lockId} is waiting
* in the queue or running, this method will block until that command finish. Therefore different
* commands with same {@code hash} will be executed in order of calling this method.
*
* If multiple caller are waiting for a command to finish, there are no guarantee that the
* earliest call will win.
*
* @param lockId of the {@code command}, if null then a random hash will be generated
* @param command the runnable task
* @throws RejectedExecutionException if this task cannot be accepted for execution
*/
public void execute(Integer lockId, Runnable command) {
try {
sparseStripedLock.add(lockId);
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
return;
}
try {
if (ExecutorUtil.isShutdown(delegate)) throw new RejectedExecutionException();
delegate.execute(
() -> {
try {
command.run();
} finally {
sparseStripedLock.remove(lockId);
}
});
} catch (RejectedExecutionException e) {
sparseStripedLock.remove(lockId);
throw e;
}
}
public void shutdownAndAwaitTermination() {
ExecutorUtil.shutdownAndAwaitTermination(delegate);
}
/**
* A set of locks by a key {@code T}, kind of like Google Striped but the keys are sparse/lazy.
*/
private static class SparseStripedLock {
private ConcurrentHashMap map = new ConcurrentHashMap<>();
private final Semaphore sizeSemaphore;
SparseStripedLock(int maxSize) {
this.sizeSemaphore = new Semaphore(maxSize);
}
public void add(T t) throws InterruptedException {
if (t != null) {
CountDownLatch myLock = new CountDownLatch(1);
CountDownLatch existingLock = map.putIfAbsent(t, myLock);
while (existingLock != null) {
// wait for existing lock/permit to become available (see remove() below)
existingLock.await();
existingLock = map.putIfAbsent(t, myLock);
}
// myLock was successfully inserted
}
// won the lock
try {
sizeSemaphore.acquire();
} catch (InterruptedException e) {
if (t != null) {
map.remove(t).countDown();
}
throw e;
}
}
public void remove(T t) {
if (t != null) {
// remove and signal to any "await"-ers
map.remove(t).countDown();
}
sizeSemaphore.release();
}
}
}