org.apache.hama.monitor.Federator.java Source code

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Here is the source code for org.apache.hama.monitor.Federator.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.hama.monitor;

import java.util.concurrent.BlockingQueue;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
import java.util.concurrent.LinkedBlockingQueue;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hama.HamaConfiguration;

public final class Federator extends Thread {

    public static final Log LOG = LogFactory.getLog(Federator.class);

    private final ExecutorService workers;
    private final BlockingQueue<Act> commands = new LinkedBlockingQueue<Act>();

    private static class ServiceWorker implements Callable<Object> {

        final Collector collector;

        public ServiceWorker(final Collector collector) {
            this.collector = collector;
        }

        @Override
        public Object call() throws Exception {
            return this.collector.harvest();
        }

    }

    /**
     * A token binds collector and handler together.
     */
    public static final class Act {
        final Collector collector;
        final CollectorHandler handler;

        public Act(final Collector collector, final CollectorHandler handler) {
            this.collector = collector;
            this.handler = handler;
        }

        public final Collector collector() {
            return this.collector;
        }

        public final CollectorHandler handler() {
            return this.handler;
        }

    }

    /**
     * Purpose to handle the result returned by Collector.
     */
    public static interface CollectorHandler {

        /**
         * Handle the result.
         */
        void handle(Future<Object> future);

    }

    /**
     * Collect GroomServer information from repository.
     */
    public static interface Collector {

        /**
         * Function is called to collect GroomServer information from specific
         * place.
         */
        Object harvest() throws Exception;

    }

    public Federator(final HamaConfiguration configuration) {
        this.workers = Executors.newCachedThreadPool();
        setName(Federator.class.getSimpleName());
        setDaemon(true);
    }

    public final void register(final Act act) {
        try {
            if (null == act || null == act.collector() || null == act.handler())
                throw new NullPointerException("Collector or CollectorHandler " + " is not provided.");
            commands.put(act);
        } catch (InterruptedException ie) {
            LOG.error(ie);
            Thread.currentThread().interrupt();
        }
    }

    @Override
    public void run() {
        try {
            while (!Thread.interrupted()) {
                Act act = commands.take();
                act.handler().handle(workers.submit(new ServiceWorker(act.collector())));
            }
        } catch (InterruptedException ie) {
            LOG.error(ie);
            Thread.currentThread().interrupt();
        }
    }

}