com.netflix.spectator.impl.StepLong Maven / Gradle / Ivy
/**
* Copyright 2015 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.impl;
import com.netflix.spectator.api.Clock;
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.
*/
public class StepLong {
private final long init;
private final Clock clock;
private final long step;
private final AtomicLong previous;
private final AtomicLong current;
private final AtomicLong lastInitPos;
/** Create a new instance. */
public StepLong(long init, Clock clock, long step) {
this.init = init;
this.clock = clock;
this.step = step;
previous = new AtomicLong(init);
current = new AtomicLong(init);
lastInitPos = new AtomicLong(clock.wallTime() / step);
}
private void rollCount(long now) {
final long stepTime = now / step;
final long lastInit = lastInitPos.get();
if (lastInit < stepTime && lastInitPos.compareAndSet(lastInit, stepTime)) {
final long v = current.getAndSet(init);
// Need to check if there was any activity during the previous step interval. If there was
// then the init position will move forward by 1, otherwise it will be older. No activity
// means the previous interval should be set to the `init` value.
previous.set((lastInit == stepTime - 1) ? v : init);
}
}
/** Get the AtomicLong for the current bucket. */
public AtomicLong getCurrent() {
rollCount(clock.wallTime());
return current;
}
/** Get the value for the last completed interval. */
public long poll() {
rollCount(clock.wallTime());
return previous.get();
}
@Override public String toString() {
return "StepLong{init=" + init
+ ", previous=" + previous.get()
+ ", current=" + current.get()
+ ", lastInitPos=" + lastInitPos.get() + '}';
}
}