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/**
* Copyright 2017 Pivotal Software, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package io.micrometer.core.instrument;
import io.micrometer.core.instrument.step.StepLong;
/**
* Used to measure absolute and relative time.
*
* @see MockClock for a clock that can be manually advanced for use in tests.
* @author Jon Schneider
*/
public interface Clock {
Clock SYSTEM = new Clock() {
@Override
public long wallTime() {
return System.currentTimeMillis();
}
@Override
public long monotonicTime() {
return System.nanoTime();
}
};
/**
* Current wall time in milliseconds since the epoch. Typically equivalent to
* System.currentTimeMillis. Should not be used to determine durations. Used
* for timestamping metrics being pushed to a monitoring system or for determination
* of step boundaries (e.g. {@link StepLong}.
*
* @return Wall time in milliseconds
*/
long wallTime();
/**
* Current time from a monotonic clock source. The value is only meaningful when compared with
* another snapshot to determine the elapsed time for an operation. The difference between two
* samples will have a unit of nanoseconds. The returned value is typically equivalent to
* System.nanoTime.
*
* @return Monotonic time in nanoseconds
*/
long monotonicTime();
}