org.apache.twill.internal.CompositeService.java Source code

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Here is the source code for org.apache.twill.internal.CompositeService.java

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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.twill.internal;

import com.google.common.base.Throwables;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.Iterables;
import com.google.common.util.concurrent.AbstractIdleService;
import com.google.common.util.concurrent.Service;
import com.google.common.util.concurrent.UncheckedExecutionException;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.ArrayDeque;
import java.util.Deque;
import java.util.Iterator;

/**
 * A {@link Service} that starts/stops list of services in order.
 */
public final class CompositeService extends AbstractIdleService {

    private static final Logger LOG = LoggerFactory.getLogger(CompositeService.class);
    private final Deque<Service> services;

    public CompositeService(Service... services) {
        this(ImmutableList.copyOf(services));
    }

    public CompositeService(Iterable<? extends Service> services) {
        this.services = new ArrayDeque<Service>();
        Iterables.addAll(this.services, services);
    }

    @Override
    protected void startUp() throws Exception {
        Throwable failureCause = null;

        for (Service service : services) {
            try {
                service.startAndWait();
            } catch (UncheckedExecutionException e) {
                failureCause = e.getCause();
                break;
            }
        }

        if (failureCause != null) {
            // Stop all running services and then throw the failure exception
            try {
                stopAll();
            } catch (Throwable t) {
                // Ignore the stop error. Just log.
                LOG.warn("Failed when stopping all services on start failure", t);
            }

            Throwables.propagateIfPossible(failureCause, Exception.class);
            throw new RuntimeException(failureCause);
        }
    }

    @Override
    protected void shutDown() throws Exception {
        stopAll();
    }

    private void stopAll() throws Exception {
        Throwable failureCause = null;

        // Stop services in reverse order.
        Iterator<Service> itor = services.descendingIterator();
        while (itor.hasNext()) {
            Service service = itor.next();
            try {
                if (service.isRunning() || service.state() == State.STARTING) {
                    service.stopAndWait();
                }
            } catch (UncheckedExecutionException e) {
                // Just catch as we want all services stopped
                if (failureCause == null) {
                    failureCause = e.getCause();
                } else {
                    // Log for sub-sequence service shutdown error, as only the first failure cause will be thrown.
                    LOG.warn("Failed to stop service {}", service, e);
                }
            }
        }

        if (failureCause != null) {
            Throwables.propagateIfPossible(failureCause, Exception.class);
            throw new RuntimeException(failureCause);
        }
    }
}