com.twitter.common.stats.NumericStatExporter.java Source code

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Here is the source code for com.twitter.common.stats.NumericStatExporter.java

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// =================================================================================================
// Copyright 2012 Twitter, Inc.
// -------------------------------------------------------------------------------------------------
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this work except in compliance with the License.
// You may obtain a copy of the License in the LICENSE file, or 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.common.stats;

import java.util.Map;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;
import java.util.logging.Logger;

import com.google.common.base.Function;
import com.google.common.collect.Maps;

import com.twitter.common.application.ShutdownRegistry;
import com.twitter.common.base.Closure;
import com.twitter.common.base.Command;
import com.twitter.common.quantity.Amount;
import com.twitter.common.quantity.Time;

import static com.google.common.base.Preconditions.checkNotNull;

/**
 * Stat exporter that extracts numeric {@link Stat}s from the {@link Stats} system, and exports them
 * via a caller-defined sink.
 *
 * @author William Farner
 */
public class NumericStatExporter {

    private static final Logger LOG = Logger.getLogger(NumericStatExporter.class.getName());

    private final ScheduledExecutorService executor;
    private final Amount<Long, Time> exportInterval;
    private final Closure<Map<String, ? extends Number>> exportSink;

    private final Runnable exporter;

    /**
     * Creates a new numeric stat exporter that will export to the specified sink.
     *
     * @param exportSink Consumes stats.
     * @param executor Executor to handle export thread.
     * @param exportInterval Export period.
     */
    public NumericStatExporter(final Closure<Map<String, ? extends Number>> exportSink,
            ScheduledExecutorService executor, Amount<Long, Time> exportInterval) {
        checkNotNull(exportSink);
        this.executor = checkNotNull(executor);
        this.exportInterval = checkNotNull(exportInterval);
        this.exportSink = exportSink;

        exporter = new Runnable() {
            @Override
            public void run() {
                exportSink.execute(
                        Maps.transformValues(Maps.uniqueIndex(Stats.getNumericVariables(), GET_NAME), READ_STAT));
            }
        };
    }

    /**
     * Starts the stat exporter.
     *
     * @param shutdownRegistry Shutdown hook registry to allow the exporter to cleanly halt.
     */
    public void start(ShutdownRegistry shutdownRegistry) {
        long intervalSecs = exportInterval.as(Time.SECONDS);
        executor.scheduleAtFixedRate(exporter, intervalSecs, intervalSecs, TimeUnit.SECONDS);

        shutdownRegistry.addAction(new Command() {
            @Override
            public void execute() {
                stop();
                exportSink.execute(Maps.transformValues(Maps.uniqueIndex(Stats.getNumericVariables(), GET_NAME),
                        SAMPLE_AND_READ_STAT));
            }
        });
    }

    /**
     * Stops the stat exporter.  Once stopped, it may be started again by calling
     * {@link #start(ShutdownRegistry)}.
     */
    public void stop() {
        try {
            if (!executor.awaitTermination(1, TimeUnit.SECONDS)) {
                executor.shutdownNow();
                if (!executor.awaitTermination(1, TimeUnit.SECONDS)) {
                    LOG.severe("Failed to stop stat exporter.");
                }
            }
        } catch (InterruptedException e) {
            executor.shutdownNow();
            Thread.currentThread().interrupt();
        }
    }

    public static final Function<Stat<?>, String> GET_NAME = new Function<Stat<?>, String>() {
        @Override
        public String apply(Stat<?> stat) {
            return stat.getName();
        }
    };

    public static final Function<Stat<? extends Number>, Number> READ_STAT = new Function<Stat<? extends Number>, Number>() {
        @Override
        public Number apply(Stat<? extends Number> stat) {
            return stat.read();
        }
    };

    private static final Function<RecordingStat<? extends Number>, Number> SAMPLE_AND_READ_STAT = new Function<RecordingStat<? extends Number>, Number>() {
        @Override
        public Number apply(RecordingStat<? extends Number> stat) {
            return stat.sample();
        }
    };
}