org.jgroups.util.TimeService Maven / Gradle / Ivy
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This artifact provides a single jar that contains all classes required to use remote EJB and JMS, including
all dependencies. It is intended for use by those not using maven, maven users should just import the EJB and
JMS BOM's instead (shaded JAR's cause lots of problems with maven, as it is very easy to inadvertently end up
with different versions on classes on the class path).
package org.jgroups.util;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
/**
* Provides a coarse grained time service. Registers a timer task which calls and caches {@link System#nanoTime()}
* and returns the cached value. This is way faster than calling {@link System#nanoTime()} many times, e.g.
* for each received message. The granularity (interval) can be chosen by the user.
* Note that use of values returned by {@link #timestamp()} needs to obey the same rules as for {@link System#nanoTime()}
* @author Bela Ban
* @since 3.5
*/
public class TimeService implements Runnable {
protected TimeScheduler timer;
protected Future task;
protected long interval=500; // ms
protected volatile long timestamp=System.nanoTime(); // ns
protected final Lock lock=new ReentrantLock();
public TimeService(final TimeScheduler timer) {
this(timer, 500);
}
public TimeService(final TimeScheduler timer, long interval) {
this.timer=timer;
this.interval=interval;
if(timer == null)
throw new IllegalArgumentException("timer must not be null");
}
/**
* Returns the timestamp (ns). Because timestamp is volatile, the read will return the result of the most recent write
* @return the result of the last call to {@link System#nanoTime()} (ns)
*/
public long timestamp() {return timestamp;}
public long interval() {
return interval;
}
public TimeService interval(long interval) {
if(interval != this.interval)
this.interval=interval;
return this;
}
public boolean running() {
lock.lock();
try {
return task != null && !task.isDone();
}
finally {
lock.unlock();
}
}
public TimeService start() {
lock.lock();
try {
if(task == null || task.isDone())
task=timer.scheduleWithFixedDelay(this, interval, interval, TimeUnit.MILLISECONDS, false);
return this;
}
finally {
lock.unlock();
}
}
public TimeService stop() {
lock.lock();
try {
if(task != null) {
task.cancel(false);
task=null;
}
return this;
}
finally {
lock.unlock();
}
}
public void run() {
timestamp=System.nanoTime(); // JLS 17.7: the write to the volatile var makes the change visible to the next read
}
public String toString() {
return getClass().getSimpleName() + " (interval=" + interval + "ms)";
}
}