io.opentelemetry.sdk.internal.MonotonicClock Maven / Gradle / Ivy
/*
* Copyright The OpenTelemetry Authors
* SPDX-License-Identifier: Apache-2.0
*/
package io.opentelemetry.sdk.internal;
import io.opentelemetry.sdk.common.Clock;
import javax.annotation.concurrent.Immutable;
/**
* This class provides a mechanism for calculating the epoch time using {@link System#nanoTime()}
* and a reference epoch timestamp.
*
* This is needed because Java has millisecond granularity for epoch times and tracing events are
* recorded more often.
*
*
This clock needs to be re-created periodically in order to re-sync with the kernel clock, and
* it is not recommended to use only one instance for a very long period of time.
*/
@Immutable
public final class MonotonicClock implements Clock {
private final Clock clock;
private final long epochNanos;
private final long nanoTime;
private MonotonicClock(Clock clock, long epochNanos, long nanoTime) {
this.clock = clock;
this.epochNanos = epochNanos;
this.nanoTime = nanoTime;
}
/**
* Returns a {@code MonotonicClock}.
*
* @param clock the {@code Clock} to be used to read the current epoch time and nanoTime.
* @return a {@code MonotonicClock}.
*/
public static MonotonicClock create(Clock clock) {
return new MonotonicClock(clock, clock.now(), clock.nanoTime());
}
/**
* Returns the current epoch timestamp in nanos calculated using {@link System#nanoTime()} since
* the reference time read in the constructor.
*
* @return the current epoch timestamp in nanos.
*/
@Override
public long now() {
long deltaNanos = clock.nanoTime() - this.nanoTime;
return epochNanos + deltaNanos;
}
@Override
public long nanoTime() {
return clock.nanoTime();
}
}