com.netflix.servo.publish.PollScheduler Maven / Gradle / Ivy
/**
* Copyright 2013 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.servo.publish;
import com.netflix.servo.util.ThreadFactories;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicReference;
/**
* Basic scheduler for polling metrics and reporting them to observers. You
* can add {@link PollRunnable} objects but not remove them individually.
* If you stop the instance and then start it again all of the prior tasks
* will be thrown away.
*/
public final class PollScheduler {
private static final PollScheduler INSTANCE = new PollScheduler();
/**
* Return the instance of this scheduler.
*/
public static PollScheduler getInstance() {
return INSTANCE;
}
private PollScheduler() {
}
private final AtomicReference executor =
new AtomicReference<>();
/**
* Add a tasks to execute at a fixed rate based on the provided delay.
*/
public void addPoller(PollRunnable task, long delay, TimeUnit timeUnit) {
ScheduledExecutorService service = executor.get();
if (service != null) {
service.scheduleWithFixedDelay(task, 0, delay, timeUnit);
} else {
throw new IllegalStateException(
"you must start the scheduler before tasks can be submitted");
}
}
/**
* Start scheduling tasks with a default thread pool, sized based on the
* number of available processors.
*/
public void start() {
int numThreads = Runtime.getRuntime().availableProcessors();
ThreadFactory factory = ThreadFactories.withName("ServoPollScheduler-%d");
start(Executors.newScheduledThreadPool(numThreads, factory));
}
/**
* Start the poller with the given executor service.
*/
public void start(ScheduledExecutorService service) {
if (!executor.compareAndSet(null, service)) {
throw new IllegalStateException("cannot start scheduler again without stopping it");
}
}
/**
* Stop the poller, shutting down the current executor service.
*/
public void stop() {
ScheduledExecutorService service = executor.get();
if (service != null && executor.compareAndSet(service, null)) {
service.shutdown();
} else {
throw new IllegalStateException("scheduler must be started before you stop it");
}
}
/**
* Returns true if this scheduler is currently started.
*/
public boolean isStarted() {
return executor.get() != null;
}
}