Timer.java

/**
 * 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 org.springframework.metrics.instrument;

import java.util.concurrent.Callable;
import java.util.concurrent.TimeUnit;

/**
 * Timer intended to track a large number of short running events. Example would be something like
 * an http request. Though "short running" is a bit subjective the assumption is that it should be
 * under a minute.
 */
public interface Timer extends Meter {
    /**
     * Updates the statistics kept by the counter with the specified amount.
     *
     * @param amount Duration of a single event being measured by this timer. If the amount is less than 0
     *               the value will be dropped.
     * @param unit   Time unit for the amount being recorded.
     */
    void record(long amount, TimeUnit unit);

    /**
     * Executes the callable `f` and records the time taken.
     *
     * @param f Function to execute and measure the execution time.
     * @return The return value of `f`.
     */
    <T> T recordThrowable(ThrowableCallable<T> f) throws Throwable;

    /**
     * Executes the runnable `f` and records the time taken.
     *
     * @param f Function to execute and measure the execution time.
     */
    void record(Runnable f);

    /**
     * The number of times that record has been called since this timer was created.
     */
    long count();

    /**
     * The total time of all recorded events since this timer was created.
     */
    double totalTime(TimeUnit unit);

    /**
     * The total time in nanoseconds of all recorded events since this timer was created.
     */
    default double totalTimeNanos() {
        return totalTime(TimeUnit.NANOSECONDS);
    }
}