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

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Here is the source code for org.apache.twill.internal.ListenerExecutor.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.collect.Maps;
import com.google.common.util.concurrent.Service;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.Executor;

/**
 * Wrapper for {@link Service.Listener} to have callback executed on a given {@link Executor}.
 * Also make sure each method is called at most once.
 */
final class ListenerExecutor implements Service.Listener {

    private static final Logger LOG = LoggerFactory.getLogger(ListenerExecutor.class);

    private final Service.Listener delegate;
    private final Executor executor;
    private final ConcurrentMap<Service.State, Boolean> callStates = Maps.newConcurrentMap();

    ListenerExecutor(Service.Listener delegate, Executor executor) {
        this.delegate = delegate;
        this.executor = executor;
    }

    @Override
    public void starting() {
        if (hasCalled(Service.State.STARTING)) {
            return;
        }
        executor.execute(new Runnable() {
            @Override
            public void run() {
                try {
                    delegate.starting();
                } catch (Throwable t) {
                    LOG.warn("Exception thrown from listener", t);
                }
            }
        });
    }

    @Override
    public void running() {
        if (hasCalled(Service.State.RUNNING)) {
            return;
        }
        executor.execute(new Runnable() {
            @Override
            public void run() {
                try {
                    delegate.running();
                } catch (Throwable t) {
                    LOG.warn("Exception thrown from listener", t);
                }
            }
        });
    }

    @Override
    public void stopping(final Service.State from) {
        if (hasCalled(Service.State.STOPPING)) {
            return;
        }
        executor.execute(new Runnable() {
            @Override
            public void run() {
                try {
                    delegate.stopping(from);
                } catch (Throwable t) {
                    LOG.warn("Exception thrown from listener", t);
                }
            }
        });
    }

    @Override
    public void terminated(final Service.State from) {
        if (hasCalled(Service.State.TERMINATED)) {
            return;
        }
        executor.execute(new Runnable() {
            @Override
            public void run() {
                try {
                    delegate.terminated(from);
                } catch (Throwable t) {
                    LOG.warn("Exception thrown from listener", t);
                }
            }
        });
    }

    @Override
    public void failed(final Service.State from, final Throwable failure) {
        // Both failed and terminate are using the same state for checking as only either one could be called.
        if (hasCalled(Service.State.TERMINATED)) {
            return;
        }
        executor.execute(new Runnable() {
            @Override
            public void run() {
                try {
                    delegate.failed(from, failure);
                } catch (Throwable t) {
                    LOG.warn("Exception thrown from listener", t);
                }
            }
        });
    }

    private boolean hasCalled(Service.State state) {
        return callStates.putIfAbsent(state, true) != null;
    }
}