com.uber.jaeger.utils.RateLimiter 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;

public class RateLimiter {
  private final double creditsPerNanosecond;
  private final Clock clock;
  private double balance;
  private double maxBalance;
  private long lastTick;

  public RateLimiter(double creditsPerSecond, double maxBalance) {
    this(creditsPerSecond, maxBalance, new SystemClock());
  }

  public RateLimiter(double creditsPerSecond, double maxBalance, Clock clock) {
    this.clock = clock;
    this.balance = maxBalance;
    this.maxBalance = maxBalance;
    this.creditsPerNanosecond = creditsPerSecond / 1.0e9;
  }

  public boolean checkCredit(double itemCost) {
    long currentTime = clock.currentNanoTicks();
    double elapsedTime = currentTime - lastTick;
    lastTick = currentTime;
    balance += elapsedTime * creditsPerNanosecond;
    if (balance > maxBalance) {
      balance = maxBalance;
    }
    if (balance >= itemCost) {
      balance -= itemCost;
      return true;
    }
    return false;
  }
}