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   * Licensed to the Apache Software Foundation (ASF) under one
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   * 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,
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   * See the License for the specific language governing permissions and
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  package com.datastax.oss.driver.core.throttling;
  
  import static org.assertj.core.api.Assertions.assertThat;
  import static org.assertj.core.api.Assertions.catchThrowable;
  
  import com.datastax.oss.driver.api.core.CqlSession;
  import com.datastax.oss.driver.api.core.RequestThrottlingException;
  import com.datastax.oss.driver.api.core.config.DefaultDriverOption;
  import com.datastax.oss.driver.api.core.config.DriverConfigLoader;
  import com.datastax.oss.driver.api.core.cql.AsyncResultSet;
  import com.datastax.oss.driver.api.testinfra.session.SessionUtils;
  import com.datastax.oss.driver.api.testinfra.simulacron.SimulacronRule;
  import com.datastax.oss.driver.categories.ParallelizableTests;
  import com.datastax.oss.driver.internal.core.session.throttling.ConcurrencyLimitingRequestThrottler;
  import com.datastax.oss.simulacron.common.cluster.ClusterSpec;
  import com.datastax.oss.simulacron.common.stubbing.PrimeDsl;
  import java.util.concurrent.CompletionStage;
  import java.util.concurrent.TimeUnit;
  import org.junit.Before;
  import org.junit.Rule;
  import org.junit.Test;
  import org.junit.experimental.categories.Category;
  
  @Category(ParallelizableTests.class)
  public class ThrottlingIT {
  
    private static final String QUERY = "select * from foo";
    private static final int maxConcurrentRequests = 10;
    private static final int maxQueueSize = 10;
  
    @Rule public SimulacronRule simulacron = new SimulacronRule(ClusterSpec.builder().withNodes(1));
  
    private DriverConfigLoader loader = null;
  
    @Before
    public void setUp() {
      // Add a delay so that requests don't complete during the test
      simulacron
          .cluster()
          .prime(PrimeDsl.when(QUERY).then(PrimeDsl.noRows()).delay(5, TimeUnit.SECONDS));
      loader =
          SessionUtils.configLoaderBuilder()
              .withClass(
                  DefaultDriverOption.REQUEST_THROTTLER_CLASS,
                  ConcurrencyLimitingRequestThrottler.class)
              .withInt(
                  DefaultDriverOption.REQUEST_THROTTLER_MAX_CONCURRENT_REQUESTS,
                  maxConcurrentRequests)
              .withInt(DefaultDriverOption.REQUEST_THROTTLER_MAX_QUEUE_SIZE, maxQueueSize)
              .build();
    }
  
    @Test
    public void should_reject_request_when_throttling_by_concurrency() {
      try (CqlSession session = SessionUtils.newSession(simulacron, loader)) {
  
        // Saturate the session and fill the queue
        for (int i = 0; i < maxConcurrentRequests + maxQueueSize; i++) {
          session.executeAsync(QUERY);
        }
  
        // The next query should be rejected
        Throwable t = catchThrowable(() -> session.execute(QUERY));
  
        assertThat(t)
            .isInstanceOf(RequestThrottlingException.class)
            .hasMessage(
                "The session has reached its maximum capacity "
                    + "(concurrent requests: 10, queue size: 10)");
      }
    }
  
    @Test
    public void should_propagate_cancel_to_throttler() {
      try (CqlSession session = SessionUtils.newSession(simulacron, loader)) {
  
        // Try to saturate the session and fill the queue
        for (int i = 0; i < maxConcurrentRequests + maxQueueSize; i++) {
          CompletionStage<AsyncResultSet> future = session.executeAsync(QUERY);
          future.toCompletableFuture().cancel(true);
        }
  
        // The next query should be successful, because the previous queries were cancelled
        session.execute(QUERY);
      }
    }
  }
  