content: /*
   * 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 org.apache.cassandra.utils.concurrent;
  
  import com.google.common.base.Ticker;
  import org.junit.Before;
  import org.junit.Test;
  
  import java.util.concurrent.TimeUnit;
  import java.util.concurrent.atomic.AtomicLong;
  
  import static org.junit.Assert.assertEquals;
  import static org.junit.Assert.assertFalse;
  import static org.junit.Assert.assertTrue;
  
  @SuppressWarnings("UnstableApiUsage")
  public class NonBlockingRateLimiterTest
  {
      private static final AtomicLong CLOCK = new AtomicLong(0);
      private static final TimeUnit DELAY_UNIT = TimeUnit.NANOSECONDS;
  
      private static final Ticker TICKER = new Ticker()
      {
          @Override
          public long read() {
              return CLOCK.get();
          }
      };
  
      @Before
      public void resetTicker()
      {
          CLOCK.set(0);
      }
  
      @Test
      public void testUnconditionalReservation()
      {
          NonBlockingRateLimiter limiter = new NonBlockingRateLimiter(4, 0, TICKER);
          long oneSecond = DELAY_UNIT.convert(1, TimeUnit.SECONDS);
          long oneDelay = oneSecond / 4;
  
          // Delays should begin accumulating without any ticker movement...
          assertEquals(0, limiter.reserveAndGetDelay(DELAY_UNIT));
          assertEquals(oneDelay, limiter.reserveAndGetDelay(DELAY_UNIT));
          assertEquals(oneDelay * 2, limiter.reserveAndGetDelay(DELAY_UNIT));
          assertEquals(oneDelay * 3, limiter.reserveAndGetDelay(DELAY_UNIT));
  
          // ...but should be gone after advancing enough to free up a permit.
          CLOCK.addAndGet(NonBlockingRateLimiter.NANOS_PER_SECOND);
          assertEquals(0, limiter.reserveAndGetDelay(DELAY_UNIT));
      }
  
      @Test
      public void testConditionalReservation()
      {
          NonBlockingRateLimiter limiter = new NonBlockingRateLimiter(1, 0, TICKER);
          
          // Take the available permit, but then fail a subsequent attempt.
          assertTrue(limiter.tryReserve());
          assertFalse(limiter.tryReserve());
  
          // We only need to advance one second, as the second attempt should not get a permit.
          CLOCK.addAndGet(NonBlockingRateLimiter.NANOS_PER_SECOND);
          assertTrue(limiter.tryReserve());
      }
  
      @Test
      public void testBurstPermitConsumption()
      {
          // Create a limiter that produces 2 permits/second and allows 1-second bursts.
          NonBlockingRateLimiter limiter = new NonBlockingRateLimiter(1, NonBlockingRateLimiter.DEFAULT_BURST_NANOS, TICKER);
  
          // Advance the clock to create a 1-second idle period, which makes one burst permit available.
          CLOCK.addAndGet(NonBlockingRateLimiter.NANOS_PER_SECOND);
          
          // Take the burst permit.
          assertTrue(limiter.tryReserve());
          
          // Take the "normal" permit.
          assertTrue(limiter.tryReserve());
          
          // Then fail, as we've consumed both.
          assertFalse(limiter.tryReserve());
  
          // Advance 1 interval again...
          CLOCK.addAndGet(NonBlockingRateLimiter.NANOS_PER_SECOND);
  
          // ...and only one permit should be available, as we've reached a steady state.
          assertTrue(limiter.tryReserve());
          assertFalse(limiter.tryReserve());
      }
  
      @Test(expected = IllegalArgumentException.class)
      public void testMaximumRate()
      {
          new NonBlockingRateLimiter(Integer.MAX_VALUE, 0, Ticker.systemTicker());
      }
  
      @Test(expected = IllegalArgumentException.class)
      public void testMinimumRate()
      {
          new NonBlockingRateLimiter(-1, 0, Ticker.systemTicker());
      }
  }
  