com.netflix.spectator.api.patterns.GaugePoller Maven / Gradle / Ivy
/*
* Copyright 2014-2017 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.api.patterns;
import java.lang.ref.WeakReference;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.atomic.AtomicReference;
import java.util.function.Consumer;
/**
* Helper for polling gauges in a background thread. A shared executor is used with a
* single thread. If registered gauge methods are cheap as they should be, then this
* should be plenty of capacity to process everything regularly. If not, then this will
* help limit the damage to a single core and avoid causing problems for the application.
*/
final class GaugePoller {
private static final ThreadFactory FACTORY = new ThreadFactory() {
private final AtomicInteger next = new AtomicInteger();
@Override public Thread newThread(Runnable r) {
final String name = "spectator-gauge-polling-" + next.getAndIncrement();
final Thread t = new Thread(r, name);
t.setDaemon(true);
return t;
}
};
private static final ScheduledExecutorService DEFAULT_EXECUTOR =
Executors.newSingleThreadScheduledExecutor(FACTORY);
/** Schedule collection of gauges for a registry. */
static void schedule(WeakReference ref, long delay, Consumer poll) {
schedule(DEFAULT_EXECUTOR, ref, delay, poll);
}
/** Schedule collection of gauges for a registry. */
@SuppressWarnings("PMD")
static void schedule(
ScheduledExecutorService executor, WeakReference ref, long delay, Consumer poll) {
final AtomicReference> futureRef = new AtomicReference<>();
final Runnable cancel = () -> {
Future f = futureRef.get();
if (f != null) {
f.cancel(false);
}
};
final Runnable task = () -> {
try {
T r = ref.get();
if (r != null) {
poll.accept(r);
} else {
cancel.run();
}
} catch (Throwable t) {
cancel.run();
}
};
futureRef.set(executor.scheduleWithFixedDelay(task, delay, delay, TimeUnit.MILLISECONDS));
}
private GaugePoller() {
}
}