| /** |
| * 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 com.twitter.distributedlog.util; |
| |
| import com.google.common.base.Preconditions; |
| |
| import com.twitter.util.Function0; |
| import com.twitter.util.FuturePool; |
| import com.twitter.util.Future; |
| |
| import org.slf4j.Logger; |
| import org.slf4j.LoggerFactory; |
| |
| import java.util.concurrent.ConcurrentLinkedQueue; |
| import java.util.concurrent.RejectedExecutionException; |
| import java.util.concurrent.atomic.AtomicInteger; |
| |
| import scala.runtime.BoxedUnit; |
| |
| /** |
| * Acts like a future pool, but collects failed apply calls into a queue to be applied |
| * in-order on close. This happens either in the close thread or after close is called, |
| * in the last operation to complete execution. |
| * Ops submitted after close will not be scheduled, so its important to ensure no more |
| * ops will be applied once close has been called. |
| */ |
| public class SafeQueueingFuturePool<T> { |
| |
| static final Logger LOG = LoggerFactory.getLogger(SafeQueueingFuturePool.class); |
| |
| private boolean closed; |
| private int outstanding; |
| private ConcurrentLinkedQueue<Function0<T>> queue; |
| private FuturePool orderedFuturePool; |
| |
| public SafeQueueingFuturePool(FuturePool orderedFuturePool) { |
| this.closed = false; |
| this.outstanding = 0; |
| this.queue = new ConcurrentLinkedQueue<Function0<T>>(); |
| this.orderedFuturePool = orderedFuturePool; |
| } |
| |
| public synchronized Future<T> apply(final Function0<T> fn) { |
| Preconditions.checkNotNull(fn); |
| if (closed) { |
| return Future.exception(new RejectedExecutionException("Operation submitted to closed SafeQueueingFuturePool")); |
| } |
| ++outstanding; |
| queue.add(fn); |
| Future<T> result = orderedFuturePool.apply(new Function0<T>() { |
| @Override |
| public T apply() { |
| return queue.poll().apply(); |
| } |
| @Override |
| public String toString() { |
| return fn.toString(); |
| } |
| }).ensure(new Function0<BoxedUnit>() { |
| public BoxedUnit apply() { |
| if (decrOutstandingAndCheckDone()) { |
| applyAll(); |
| } |
| return null; |
| } |
| }); |
| return result; |
| } |
| |
| private synchronized boolean decrOutstandingAndCheckDone() { |
| return --outstanding == 0 && closed; |
| } |
| |
| public void close() { |
| final boolean done; |
| synchronized (this) { |
| if (closed) { |
| return; |
| } |
| closed = true; |
| done = (outstanding == 0); |
| } |
| if (done) { |
| applyAll(); |
| } |
| } |
| |
| private void applyAll() { |
| if (!queue.isEmpty()) { |
| LOG.info("Applying {} items", queue.size()); |
| } |
| while (!queue.isEmpty()) { |
| queue.poll().apply(); |
| } |
| } |
| |
| public synchronized int size() { |
| return queue.size(); |
| } |
| } |