/*
* Copyright 2014-2016 Netflix, Inc.
*
* Licensed 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 com.netflix.spectator.atlas;
import com.netflix.spectator.api.Clock;
import com.netflix.spectator.api.Id;
import com.netflix.spectator.api.Measurement;
import com.netflix.spectator.api.Statistic;
import com.netflix.spectator.api.Timer;
import com.netflix.spectator.impl.StepDouble;
import com.netflix.spectator.impl.StepLong;
import com.netflix.spectator.impl.StepValue;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.Callable;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicLong;
/**
* Timer that reports four measurements to Atlas:
*
* <ul>
* <li><b>count:</b> counter incremented each time record is called</li>
* <li><b>totalTime:</b> counter incremented by the recorded amount</li>
* <li><b>totalOfSquares:</b> counter incremented by the recorded amount<sup>2</sup></li>
* <li><b>max:</b> maximum recorded amount</li>
* </ul>
*
* <p>Having an explicit {@code totalTime} and {@code count} on the backend
* can be used to calculate an accurate average for an arbitrary grouping. The
* {@code totalOfSquares} is used for computing a standard deviation.</p>
*
* <p>Note that the {@link #count()} and {@link #totalTime()} will report
* the values since the last complete interval rather than the total for the
* life of the process.</p>
*/
class AtlasTimer implements Timer {
private final Id id;
private final Clock clock;
private final StepLong count;
private final StepLong total;
private final StepDouble totalOfSquares;
private final StepLong max;
private final Id[] stats;
/** Create a new instance. */
AtlasTimer(Id id, Clock clock, long step) {
this.id = id;
this.clock = clock;
this.count = new StepLong(0L, clock, step);
this.total = new StepLong(0L, clock, step);
this.totalOfSquares = new StepDouble(0.0, clock, step);
this.max = new StepLong(0L, clock, step);
this.stats = new Id[] {
id.withTags(DsType.rate, Statistic.count),
id.withTags(DsType.rate, Statistic.totalTime),
id.withTags(DsType.rate, Statistic.totalOfSquares),
id.withTags(DsType.gauge, Statistic.max)
};
}
@Override public Id id() {
return id;
}
@Override public boolean hasExpired() {
return false;
}
@Override public Iterable<Measurement> measure() {
List<Measurement> ms = new ArrayList<>(4);
ms.add(newMeasurement(stats[0], count, 1.0));
ms.add(newMeasurement(stats[1], total, 1e-9));
ms.add(newMeasurement(stats[2], totalOfSquares, 1e-18));
ms.add(newMaxMeasurement(stats[3], max));
return ms;
}
private Measurement newMeasurement(Id mid, StepValue v, double f) {
// poll needs to be called before accessing the timestamp to ensure
// the counters have been rotated if there was no activity in the
// current interval.
double rate = v.pollAsRate() * f;
long timestamp = v.timestamp();
return new Measurement(mid, timestamp, rate);
}
private Measurement newMaxMeasurement(Id mid, StepLong v) {
// poll needs to be called before accessing the timestamp to ensure
// the counters have been rotated if there was no activity in the
// current interval.
double maxValue = v.poll() / 1e9;
long timestamp = v.timestamp();
return new Measurement(mid, timestamp, maxValue);
}
@Override public void record(long amount, TimeUnit unit) {
count.getCurrent().incrementAndGet();
if (amount > 0) {
final long nanos = unit.toNanos(amount);
total.getCurrent().addAndGet(nanos);
totalOfSquares.getCurrent().addAndGet((double) nanos * nanos);
updateMax(max.getCurrent(), nanos);
}
}
private void updateMax(AtomicLong maxValue, long v) {
long p = maxValue.get();
while (v > p && !maxValue.compareAndSet(p, v)) {
p = maxValue.get();
}
}
@Override public <T> T record(Callable<T> f) throws Exception {
final long start = clock.monotonicTime();
try {
return f.call();
} finally {
record(clock.monotonicTime() - start, TimeUnit.NANOSECONDS);
}
}
@Override public void record(Runnable f) {
final long start = clock.monotonicTime();
try {
f.run();
} finally {
record(clock.monotonicTime() - start, TimeUnit.NANOSECONDS);
}
}
@Override public long count() {
return count.poll();
}
@Override public long totalTime() {
return total.poll();
}
}