add meter metric implementation

modules/elasticsearch/src/main/java/org/elasticsearch/common/metrics/EWMA.java

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+/*
+ * Licensed to Elastic Search and Shay Banon under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. Elastic Search 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.elasticsearch.common.metrics;
+
+import org.elasticsearch.common.util.concurrent.jsr166e.LongAdder;
+
+import java.util.concurrent.TimeUnit;
+
+/**
+ * An exponentially-weighted moving average.
+ *
+ * @see <a href="http://www.teamquest.com/pdfs/whitepaper/ldavg1.pdf">UNIX Load Average Part 1: How It Works</a>
+ * @see <a href="http://www.teamquest.com/pdfs/whitepaper/ldavg2.pdf">UNIX Load Average Part 2: Not Your Average Average</a>
+ *
+ *      Taken from codahale metric module, changed to use LongAdder
+ */
+public class EWMA {
+    private static final double M1_ALPHA = 1 - Math.exp(-5 / 60.0);
+    private static final double M5_ALPHA = 1 - Math.exp(-5 / 60.0 / 5);
+    private static final double M15_ALPHA = 1 - Math.exp(-5 / 60.0 / 15);
+
+    private volatile boolean initialized = false;
+    private volatile double rate = 0.0;
+
+    private final LongAdder uncounted = new LongAdder();
+    private final double alpha, interval;
+
+    /**
+     * Creates a new EWMA which is equivalent to the UNIX one minute load average and which expects to be ticked every
+     * 5 seconds.
+     *
+     * @return a one-minute EWMA
+     */
+    public static EWMA oneMinuteEWMA() {
+        return new EWMA(M1_ALPHA, 5, TimeUnit.SECONDS);
+    }
+
+    /**
+     * Creates a new EWMA which is equivalent to the UNIX five minute load average and which expects to be ticked every
+     * 5 seconds.
+     *
+     * @return a five-minute EWMA
+     */
+    public static EWMA fiveMinuteEWMA() {
+        return new EWMA(M5_ALPHA, 5, TimeUnit.SECONDS);
+    }
+
+    /**
+     * Creates a new EWMA which is equivalent to the UNIX fifteen minute load average and which expects to be ticked
+     * every 5 seconds.
+     *
+     * @return a fifteen-minute EWMA
+     */
+    public static EWMA fifteenMinuteEWMA() {
+        return new EWMA(M15_ALPHA, 5, TimeUnit.SECONDS);
+    }
+
+    /**
+     * Create a new EWMA with a specific smoothing constant.
+     *
+     * @param alpha        the smoothing constant
+     * @param interval     the expected tick interval
+     * @param intervalUnit the time unit of the tick interval
+     */
+    public EWMA(double alpha, long interval, TimeUnit intervalUnit) {
+        this.interval = intervalUnit.toNanos(interval);
+        this.alpha = alpha;
+    }
+
+    /**
+     * Update the moving average with a new value.
+     *
+     * @param n the new value
+     */
+    public void update(long n) {
+        uncounted.add(n);
+    }
+
+    /**
+     * Mark the passage of time and decay the current rate accordingly.
+     */
+    public void tick() {
+        final long count = uncounted.sumThenReset();
+        double instantRate = count / interval;
+        if (initialized) {
+            rate += (alpha * (instantRate - rate));
+        } else {
+            rate = instantRate;
+            initialized = true;
+        }
+    }
+
+    /**
+     * Returns the rate in the given units of time.
+     *
+     * @param rateUnit the unit of time
+     * @return the rate
+     */
+    public double rate(TimeUnit rateUnit) {
+        return rate * (double) rateUnit.toNanos(1);
+    }
+}

modules/elasticsearch/src/main/java/org/elasticsearch/common/metrics/MeterMetric.java

@@ -0,0 +1,123 @@
+/*
+ * Licensed to Elastic Search and Shay Banon under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. Elastic Search 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.elasticsearch.common.metrics;
+
+import org.elasticsearch.common.util.concurrent.jsr166e.LongAdder;
+
+import java.util.concurrent.ScheduledExecutorService;
+import java.util.concurrent.ScheduledFuture;
+import java.util.concurrent.TimeUnit;
+
+/**
+ * A meter metric which measures mean throughput and one-, five-, and
+ * fifteen-minute exponentially-weighted moving average throughputs.
+ *
+ * @see <a href="http://en.wikipedia.org/wiki/Moving_average#Exponential_moving_average">EMA</a>
+ *
+ *      taken from codahale metric module, replaced with LongAdder
+ */
+public class MeterMetric implements Metric {
+    private static final long INTERVAL = 5; // seconds
+
+    private final EWMA m1Rate = EWMA.oneMinuteEWMA();
+    private final EWMA m5Rate = EWMA.fiveMinuteEWMA();
+    private final EWMA m15Rate = EWMA.fifteenMinuteEWMA();
+
+    private final LongAdder count = new LongAdder();
+    private final long startTime = System.nanoTime();
+    private final TimeUnit rateUnit;
+    private final ScheduledFuture<?> future;
+
+    public MeterMetric(ScheduledExecutorService tickThread, TimeUnit rateUnit) {
+        this.rateUnit = rateUnit;
+        this.future = tickThread.scheduleAtFixedRate(new Runnable() {
+            @Override
+            public void run() {
+                tick();
+            }
+        }, INTERVAL, INTERVAL, TimeUnit.SECONDS);
+    }
+
+    public TimeUnit rateUnit() {
+        return rateUnit;
+    }
+
+    /**
+     * Updates the moving averages.
+     */
+    void tick() {
+        m1Rate.tick();
+        m5Rate.tick();
+        m15Rate.tick();
+    }
+
+    /**
+     * Mark the occurrence of an event.
+     */
+    public void mark() {
+        mark(1);
+    }
+
+    /**
+     * Mark the occurrence of a given number of events.
+     *
+     * @param n the number of events
+     */
+    public void mark(long n) {
+        count.add(n);
+        m1Rate.update(n);
+        m5Rate.update(n);
+        m15Rate.update(n);
+    }
+
+    public long count() {
+        return count.sum();
+    }
+
+    public double fifteenMinuteRate() {
+        return m15Rate.rate(rateUnit);
+    }
+
+    public double fiveMinuteRate() {
+        return m5Rate.rate(rateUnit);
+    }
+
+    public double meanRate() {
+        long count = count();
+        if (count == 0) {
+            return 0.0;
+        } else {
+            final long elapsed = (System.nanoTime() - startTime);
+            return convertNsRate(count / (double) elapsed);
+        }
+    }
+
+    public double oneMinuteRate() {
+        return m1Rate.rate(rateUnit);
+    }
+
+    private double convertNsRate(double ratePerNs) {
+        return ratePerNs * (double) rateUnit.toNanos(1);
+    }
+
+    public void stop() {
+        future.cancel(false);
+    }
+}