| /* |
| * 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.twill.internal; |
| |
| import com.google.common.collect.Lists; |
| import com.google.common.util.concurrent.Futures; |
| import com.google.common.util.concurrent.ListenableFuture; |
| import com.google.common.util.concurrent.Service; |
| import com.google.common.util.concurrent.SettableFuture; |
| import org.apache.twill.common.Threads; |
| |
| import java.util.List; |
| import java.util.concurrent.atomic.AtomicInteger; |
| |
| /** |
| * Utility methods for help dealing with {@link Service}. |
| */ |
| public final class Services { |
| |
| /** |
| * Starts a list of {@link Service} one by one. Starting of next Service is triggered from the callback listener |
| * thread of the previous Service. |
| * |
| * @param firstService First service to start. |
| * @param moreServices The rest services to start. |
| * @return A {@link ListenableFuture} that will be completed when all services are started, with the |
| * result carries the completed {@link ListenableFuture} of each corresponding service in the |
| * same order as they are passed to this method. |
| */ |
| public static ListenableFuture<List<ListenableFuture<Service.State>>> chainStart(Service firstService, |
| Service...moreServices) { |
| return doChain(true, firstService, moreServices); |
| } |
| |
| /** |
| * Stops a list of {@link Service} one by one. It behaves the same as |
| * {@link #chainStart(com.google.common.util.concurrent.Service, com.google.common.util.concurrent.Service...)} |
| * except {@link com.google.common.util.concurrent.Service#stop()} is called instead of start. |
| * |
| * @param firstService First service to stop. |
| * @param moreServices The rest services to stop. |
| * @return A {@link ListenableFuture} that will be completed when all services are stopped. |
| * @see #chainStart(com.google.common.util.concurrent.Service, com.google.common.util.concurrent.Service...) |
| */ |
| public static ListenableFuture<List<ListenableFuture<Service.State>>> chainStop(Service firstService, |
| Service...moreServices) { |
| return doChain(false, firstService, moreServices); |
| } |
| |
| /** |
| * Returns a {@link ListenableFuture} that will be completed when the given service is stopped. If the service |
| * stopped due to error, the failure cause would be reflected in the future. |
| * |
| * @param service The {@link Service} to block on. |
| * @return A {@link ListenableFuture} that will be completed when the service is stopped. |
| */ |
| public static ListenableFuture<Service.State> getCompletionFuture(Service service) { |
| final SettableFuture<Service.State> resultFuture = SettableFuture.create(); |
| |
| service.addListener(new ServiceListenerAdapter() { |
| @Override |
| public void terminated(Service.State from) { |
| resultFuture.set(Service.State.TERMINATED); |
| } |
| |
| @Override |
| public void failed(Service.State from, Throwable failure) { |
| resultFuture.setException(failure); |
| } |
| }, Threads.SAME_THREAD_EXECUTOR); |
| |
| Service.State state = service.state(); |
| if (state == Service.State.TERMINATED) { |
| return Futures.immediateFuture(state); |
| } else if (state == Service.State.FAILED) { |
| return Futures.immediateFailedFuture(new IllegalStateException("Service failed with unknown exception.")); |
| } |
| |
| return resultFuture; |
| } |
| |
| /** |
| * Performs the actual logic of chain Service start/stop. |
| */ |
| private static ListenableFuture<List<ListenableFuture<Service.State>>> doChain(boolean doStart, |
| Service firstService, |
| Service...moreServices) { |
| SettableFuture<List<ListenableFuture<Service.State>>> resultFuture = SettableFuture.create(); |
| List<ListenableFuture<Service.State>> result = Lists.newArrayListWithCapacity(moreServices.length + 1); |
| |
| ListenableFuture<Service.State> future = doStart ? firstService.start() : firstService.stop(); |
| future.addListener(createChainListener(future, moreServices, new AtomicInteger(0), result, resultFuture, doStart), |
| Threads.SAME_THREAD_EXECUTOR); |
| return resultFuture; |
| } |
| |
| /** |
| * Returns a {@link Runnable} that can be used as a {@link ListenableFuture} listener to trigger |
| * further service action or completing the result future. Used by |
| * {@link #doChain(boolean, com.google.common.util.concurrent.Service, com.google.common.util.concurrent.Service...)} |
| */ |
| private static Runnable createChainListener(final ListenableFuture<Service.State> future, final Service[] services, |
| final AtomicInteger idx, |
| final List<ListenableFuture<Service.State>> result, |
| final SettableFuture<List<ListenableFuture<Service.State>>> resultFuture, |
| final boolean doStart) { |
| return new Runnable() { |
| |
| @Override |
| public void run() { |
| result.add(future); |
| int nextIdx = idx.getAndIncrement(); |
| if (nextIdx == services.length) { |
| resultFuture.set(result); |
| return; |
| } |
| ListenableFuture<Service.State> actionFuture = doStart ? services[nextIdx].start() : services[nextIdx].stop(); |
| actionFuture.addListener(createChainListener(actionFuture, services, idx, result, resultFuture, doStart), |
| Threads.SAME_THREAD_EXECUTOR); |
| } |
| }; |
| } |
| |
| private Services() { |
| } |
| } |