/*
* Copyright (c) 2011-2014 Pivotal Software, 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 reactor.timer;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import reactor.event.registry.CachingRegistry;
import reactor.event.registry.Registration;
import reactor.event.registry.Registry;
import reactor.event.selector.HeaderResolver;
import reactor.event.selector.Selector;
import reactor.function.Consumer;
import reactor.function.support.CancelConsumerException;
import reactor.support.NamedDaemonThreadFactory;
import reactor.util.Assert;
import java.util.concurrent.TimeUnit;
/**
* A hashed wheel timer implementation that uses a {@link reactor.event.registry.Registry} and custom {@link
* reactor.event.selector.Selector Selectors} to determine when tasks should be executed.
* <p>
* A {@code SimpleHashWheelTimer} has two variations for scheduling tasks: {@link #schedule(reactor.function.Consumer,
* long,
* java.util.concurrent.TimeUnit)} and {@link #schedule(reactor.function.Consumer, long, java.util.concurrent.TimeUnit,
* long)} which are for scheduling repeating tasks, and {@link #submit(reactor.function.Consumer, long,
* java.util.concurrent.TimeUnit)} which is for scheduling single-run delayed tasks.
* </p>
* <p>
* To schedule a repeating task, specify the period of time which should elapse before invoking the given {@link
* reactor.function.Consumer}. To schedule a task that repeats every 5 seconds, for example, one would do something
* like:
* </p>
* <p>
* <code><pre>
* SimpleHashWheelTimer timer = new SimpleHashWheelTimer();
*
* timer.schedule(new Consumer<Long>() {
* public void accept(Long now) {
* // run a task
* }
* }, 5, TimeUnit.SECONDS);
* </pre></code>
* </p>
* <p>
* NOTE: Without delaying a task, it will be run immediately, in addition to being run after the elapsed time has
* expired. To run a task only once every N time units and not immediately, use the {@link
* #schedule(reactor.function.Consumer, long, java.util.concurrent.TimeUnit, long)} method, which allows you to specify
* an additional delay that must expire before the task will be executed.
* </p>
*
* @author Jon Brisbin
* @author Stephane Maldini
*/
public class SimpleHashWheelTimer implements Timer {
private static final Logger LOG = LoggerFactory.getLogger(SimpleHashWheelTimer.class);
private final Registry<Consumer<Long>> tasks = new CachingRegistry<Consumer<Long>>(true, false, null);
private final int resolution;
private final Thread loop;
/**
* Create a new {@code SimpleHashWheelTimer} using the default resolution of 50ms.
*/
public SimpleHashWheelTimer() {
this(50);
}
/**
* Create a new {@code SimpleHashWheelTimer} using the given timer resolution. All times will rounded up to the
* closest
* multiple of this resolution.
*
* @param resolution
* the resolution of this timer, in milliseconds
*/
public SimpleHashWheelTimer(final int resolution) {
this.resolution = resolution;
this.loop = new NamedDaemonThreadFactory("simple-hash-wheel-timer").newThread(
new Runnable() {
@Override
public void run() {
while(!Thread.currentThread().isInterrupted()) {
long now = now(resolution);
for(Registration<? extends Consumer<Long>> reg : tasks.select(now)) {
try {
if(reg.isCancelled() || reg.isPaused()) {
continue;
}
reg.getObject().accept(now);
} catch(CancelConsumerException cce) {
reg.cancel();
} catch(Throwable t) {
LOG.error(t.getMessage(), t);
} finally {
if(reg.isCancelAfterUse()) {
reg.cancel();
}
}
}
try {
Thread.sleep(resolution);
} catch(InterruptedException e) {
Thread.currentThread().interrupt();
return;
}
}
}
}
);
this.loop.start();
}
@Override
public long getResolution() {
return resolution;
}
@Override
public Registration<? extends Consumer<Long>> schedule(Consumer<Long> consumer,
long period,
TimeUnit timeUnit,
long delayInMilliseconds) {
Assert.isTrue(!loop.isInterrupted(), "Cannot submit tasks to this timer as it has been cancelled.");
long milliPeriod = TimeUnit.MILLISECONDS.convert(period, timeUnit);
Assert.isTrue(milliPeriod % resolution == 0, "Period must be a multiple of timer resolution (e.g. period % resolution == 0 )");
return tasks.register(
new PeriodSelector(milliPeriod, delayInMilliseconds, resolution),
consumer
);
}
@Override
public Registration<? extends Consumer<Long>> schedule(Consumer<Long> consumer,
long period,
TimeUnit timeUnit) {
return schedule(consumer, period, timeUnit, 0);
}
@Override
public Registration<? extends Consumer<Long>> submit(Consumer<Long> consumer,
long delay,
TimeUnit timeUnit) {
Assert.isTrue(!loop.isInterrupted(), "Cannot submit tasks to this timer as it has been cancelled.");
long ms = TimeUnit.MILLISECONDS.convert(delay, timeUnit);
return tasks.register(
new PeriodSelector(ms, ms, resolution),
consumer
).cancelAfterUse();
}
@Override
public Registration<? extends Consumer<Long>> submit(Consumer<Long> consumer) {
return submit(consumer, resolution, TimeUnit.MILLISECONDS);
}
@Override
public void cancel() {
this.loop.interrupt();
}
private static long now(int resolution) {
return (long)(Math.ceil(System.currentTimeMillis() / resolution) * resolution);
}
private static class PeriodSelector implements Selector {
private final long period;
private final long delay;
private final long createdMillis;
private final int resolution;
private PeriodSelector(long period, long delay, int resolution) {
this.period = period;
this.delay = delay;
this.resolution = resolution;
this.createdMillis = now(resolution);
}
@Override
public Object getObject() {
return period;
}
@Override
public boolean matches(Object key) {
long now = (Long)key;
long period = (long)(Math.ceil((now - createdMillis) / resolution) * resolution);
return period >= delay && period % this.period == 0;
}
@Override
public HeaderResolver getHeaderResolver() {
return null;
}
}
}