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// Copyright Verizon Media. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.concurrent.maintenance;
import com.google.common.util.concurrent.UncheckedTimeoutException;
import com.yahoo.net.HostName;
import java.time.Duration;
import java.time.Instant;
import java.util.List;
import java.util.Objects;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.ScheduledThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
import java.util.logging.Level;
import java.util.logging.Logger;
/**
* The base class for maintainers. A maintainer is some job which runs at a fixed rate to perform maintenance tasks.
*
* @author bratseth
* @author mpolden
*/
public abstract class Maintainer implements Runnable, AutoCloseable {
protected final Logger log = Logger.getLogger(this.getClass().getName());
private final String name;
private final JobControl jobControl;
private final Duration interval;
private final ScheduledExecutorService service;
public Maintainer(String name, Duration interval, Instant startedAt, JobControl jobControl, List<String> clusterHostnames) {
this(name, interval, staggeredDelay(interval, startedAt, HostName.getLocalhost(), clusterHostnames), jobControl);
}
public Maintainer(String name, Duration interval, Duration initialDelay, JobControl jobControl) {
this.name = name;
this.interval = requireInterval(interval);
this.jobControl = Objects.requireNonNull(jobControl);
service = new ScheduledThreadPoolExecutor(1, r -> new Thread(r, name() + "-worker"));
service.scheduleAtFixedRate(this, initialDelay.toMillis(), interval.toMillis(), TimeUnit.MILLISECONDS);
jobControl.started(name(), this);
}
@Override
public void run() {
try {
if (jobControl.isActive(name())) {
lockAndMaintain();
}
} catch (UncheckedTimeoutException ignored) {
// Another actor is running this job
} catch (Throwable e) {
log.log(Level.WARNING, this + " failed. Will retry in " + interval.toMinutes() + " minutes", e);
}
}
@Override
public void close() {
var timeout = Duration.ofSeconds(30);
service.shutdown();
try {
if (!service.awaitTermination(timeout.toMillis(), TimeUnit.MILLISECONDS)) {
log.log(Level.WARNING, "Maintainer " + name() + " failed to shutdown " +
"within " + timeout);
}
} catch (InterruptedException e) {
throw new RuntimeException(e);
}
}
@Override
public final String toString() { return name(); }
/** Called once each time this maintenance job should run */
protected abstract void maintain();
/** Returns the interval at which this job is set to run */
protected Duration interval() { return interval; }
/** Run this while holding the job lock */
@SuppressWarnings("unused")
public final void lockAndMaintain() {
try (var lock = jobControl.lockJob(name())) {
maintain();
}
}
/** Returns the simple name of this job */
public final String name() {
return name == null ? this.getClass().getSimpleName() : name;
}
/** Returns the initial delay of this calculated from cluster index of given hostname */
static Duration staggeredDelay(Duration interval, Instant now, String hostname, List<String> clusterHostnames) {
Objects.requireNonNull(clusterHostnames);
if ( ! clusterHostnames.contains(hostname))
return interval;
long offset = clusterHostnames.indexOf(hostname) * interval.toMillis() / clusterHostnames.size();
return Duration.ofMillis(Math.floorMod(offset - now.toEpochMilli(), interval.toMillis()));
}
private static Duration requireInterval(Duration interval) {
Objects.requireNonNull(interval);
if (interval.isNegative() || interval.isZero())
throw new IllegalArgumentException("Interval must be positive, but was " + interval);
return interval;
}
}
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