com.amlinv.javasched.process.RateLimitedSingleRepeatingStepProcess Maven / Gradle / Ivy

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Scheduler of java processes that seeks to optimize the execution of processing tasks by the JVM with minimal threads in order to reduce the overhead of context switching, optimize the utilization of CPU cores, and provide controls to the application over the scheduling of processing tasks.

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/*
 *   Copyright 2015 AML Innovation & Consulting LLC
 *
 *   Licensed to the Apache Software Foundation (ASF) under one or more
 *   contributor license agreements.  See the NOTICE file distributed with
 *   this work for additional information regarding copyright ownership.
 *   The ASF licenses this file to You 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 com.amlinv.javasched.process;

import com.amlinv.javasched.SchedulerProcess;
import com.amlinv.javasched.Step;

/**
 * Single repeating step process that additionally limits the rate at which steps are executed.
 * An example use case is aggregation of metrics collected periodically where there is a need to
 * limit the overall overhead of updating the aggregate.  Another use-case is sending a rate-
 * limited ping, health-check, or status over a connection to a client, server, or peer.
 *
 * Created by art on 6/5/15.
 */
public class RateLimitedSingleRepeatingStepProcess extends SingleRepeatingStepProcess {
  private final long ratePeriod;

  private long lastMark = 0;

  private final WaitRatePeriodCompleteStep waitRatePeriodCompleteStep =
      new WaitRatePeriodCompleteStep();

  public RateLimitedSingleRepeatingStepProcess(Step repeatableStep, boolean repeatOnlyWhenSignalled,
                                               long ratePeriod, long initialDelay) {
    super(repeatableStep, repeatOnlyWhenSignalled);
    this.ratePeriod = ratePeriod;
    this.lastMark = ( System.nanoTime() / 1000000L ) + initialDelay - ratePeriod;
  }

  public RateLimitedSingleRepeatingStepProcess(Step repeatableStep, long ratePeriod,
                                               long initialDelay) {
    super(repeatableStep);
    this.ratePeriod = ratePeriod;
    this.lastMark = ( System.nanoTime() / 1000000L ) + initialDelay - ratePeriod;
  }

  @Override
  public Step getNextStep() {
    long mark = System.nanoTime() / 1000000L;

    Step result;
    if ((mark - this.lastMark) >= this.ratePeriod) {
      this.lastMark = mark;
      result = super.getNextStep();
    } else {
      result = this.waitRatePeriodCompleteStep;
    }

    return  result;
  }

  ////////////////////
  // INTERNAL CLASSES
  ////////////////////

  protected class WaitRatePeriodCompleteStep implements Step {
    RateLimitedSingleRepeatingStepProcess parent = RateLimitedSingleRepeatingStepProcess.this;

    @Override
    public void execute() {
      long mark = System.nanoTime() / 1000000L;
      long diff = mark - parent.lastMark;

      if (diff < parent.ratePeriod) {
        try {
          Thread.sleep(parent.ratePeriod - diff);
        } catch (InterruptedException intExc) {
          throw new RuntimeException("process interrupted", intExc);
        }
      }
    }

    @Override
    public boolean isBlocking() {
      return true;
    }
  }
}