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// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.concurrent;
import java.time.Duration;
import java.util.concurrent.TimeUnit;
import java.util.logging.Level;
import java.util.logging.Logger;
/**
* This is an implementation of {@link Timer} that is backed by an actual system timer.
*
* @author Simon Thoresen Hult
*/
public enum SystemTimer implements Timer {
INSTANCE;
private volatile long millis;
public static long detectHz() {
Logger log = Logger.getLogger(SystemTimer.class.getName());
String hzEnv = System.getenv("VESPA_TIMER_HZ");
long hz = 1000;
if ((hzEnv != null) && !hzEnv.isBlank()) {
try {
hz = Integer.parseInt(hzEnv);
} catch (NumberFormatException e) {
log.log(Level.WARNING, "Failed parsing VESPA_TIMER_HZ='" + hzEnv + "'", e);
}
};
hz = Math.min(1000, Math.max(1, hz)); // Capping to valid range [1...1000]hz
log.fine("vespa-system-timer running at " + hz + "hz. VESPA_TIMER_HZ='" + hzEnv + "'");
return hz;
}
public static Duration adjustTimeoutByDetectedHz(Duration timeout) {
return adjustTimeoutByDetectedHz(timeout, detectHz());
}
public static Duration adjustTimeoutByDetectedHz(Duration timeout, long hz) {
return timeout.multipliedBy(1000).dividedBy(hz);
}
SystemTimer() {
long napTime = adjustTimeoutByDetectedHz(Duration.ofMillis(1)).toMillis();
long creationNanos = System.nanoTime();
millis = TimeUnit.NANOSECONDS.toMillis(System.nanoTime() - creationNanos);
Thread thread = new Thread(() -> {
while (true) {
millis = TimeUnit.NANOSECONDS.toMillis(System.nanoTime() - creationNanos);
try {
Thread.sleep(napTime);
} catch (InterruptedException e) {
break;
}
}
});
thread.setDaemon(true);
thread.setName("vespa-system-timer");
thread.start();
}
@Override
public long milliTime() {
return millis;
}
}
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