com.uber.jaeger.utils.Clock Maven / Gradle / Ivy

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/*
 * Copyright (c) 2016, Uber Technologies, Inc
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
package com.uber.jaeger.utils;

/**
 * A small abstraction around system clock that aims to provide microsecond precision
 * with the best accuracy possible.
 */
public interface Clock {
    /**
     * Returns the current time in microseconds.
     *
     * @return the difference, measured in microseconds, between the current time
     * and and the Epoch (that is, midnight, January 1, 1970 UTC).
     */
    long currentTimeMicros();

    /**
     * Returns the current value of the running Java Virtual Machine's
     * high-resolution time source, in nanoseconds.
     *
     * This method can only be used to measure elapsed time and is
     * not related to any other notion of system or wall-clock time.
     *
     * @return the current value of the running Java Virtual Machine's
     *         high-resolution time source, in nanoseconds
     */
    long currentNanoTicks();

    /**
     * @return true if the time returned by {@link #currentTimeMicros()}
     * is accurate enough to calculate span duration as (end-start).
     * If this method returns false, the {@code Tracer} will use
     * {@link #currentNanoTicks()} for calculating duration instead.
     */
    boolean isMicrosAccurate();
}