com.netflix.spectator.servo.StepLong Maven / Gradle / Ivy
/*
* Copyright 2014-2019 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.servo;
import com.netflix.servo.util.Clock;
import java.util.Arrays;
import java.util.concurrent.atomic.AtomicLong;
/**
* Utility class for managing a set of AtomicLong instances mapped to a particular step interval.
* The current implementation keeps an array of with two items where one is the current value
* being updated and the other is the value from the previous interval and is only available for
* polling.
*/
class StepLong {
private static final int PREVIOUS = 0;
private static final int CURRENT = 1;
private final long init;
private final Clock clock;
private final AtomicLong[] data;
private final AtomicLong[] lastPollTime;
private final AtomicLong[] lastInitPos;
/** Create a new instance. */
StepLong(long init, Clock clock) {
this.init = init;
this.clock = clock;
lastInitPos = new AtomicLong[ServoPollers.NUM_POLLERS];
lastPollTime = new AtomicLong[ServoPollers.NUM_POLLERS];
for (int i = 0; i < ServoPollers.NUM_POLLERS; ++i) {
lastInitPos[i] = new AtomicLong(0L);
lastPollTime[i] = new AtomicLong(0L);
}
data = new AtomicLong[2 * ServoPollers.NUM_POLLERS];
for (int i = 0; i < data.length; ++i) {
data[i] = new AtomicLong(init);
}
}
/** Add to the current bucket. */
void addAndGet(long amount) {
for (int i = 0; i < ServoPollers.NUM_POLLERS; ++i) {
getCurrent(i).addAndGet(amount);
}
}
private void rollCount(int pollerIndex, long now) {
final long step = ServoPollers.POLLING_INTERVALS[pollerIndex];
final long stepTime = now / step;
final long lastInit = lastInitPos[pollerIndex].get();
if (lastInit < stepTime && lastInitPos[pollerIndex].compareAndSet(lastInit, stepTime)) {
final int prev = 2 * pollerIndex + PREVIOUS;
final int curr = 2 * pollerIndex + CURRENT;
data[prev].set(data[curr].getAndSet(init));
}
}
/** Get the AtomicLong for the current bucket. */
AtomicLong getCurrent(int pollerIndex) {
rollCount(pollerIndex, clock.now());
return data[2 * pollerIndex + CURRENT];
}
/** Get the value for the last completed interval. */
Long poll(int pollerIndex) {
final long now = clock.now();
final long step = ServoPollers.POLLING_INTERVALS[pollerIndex];
rollCount(pollerIndex, now);
final int prevPos = 2 * pollerIndex + PREVIOUS;
final long value = data[prevPos].get();
final long last = lastPollTime[pollerIndex].getAndSet(now);
final long missed = (now - last) / step - 1;
if (last / step == now / step) {
return value;
} else if (last > 0L && missed > 0L) {
return null;
} else {
return value;
}
}
@Override public String toString() {
return "StepLong{init=" + init
+ ", data=" + Arrays.toString(data)
+ ", lastPollTime=" + Arrays.toString(lastPollTime)
+ ", lastInitPos=" + Arrays.toString(lastInitPos) + '}';
}
}