MarkDeadStrategyWithHostCheckTest.java

// =================================================================================================
// Copyright 2011 Twitter, Inc.
// -------------------------------------------------------------------------------------------------
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this work except in compliance with the License.
// You may obtain a copy of the License in the LICENSE file, or 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.twitter.common.net.loadbalancing;

import java.util.Collection;

import com.google.common.base.Function;
import com.google.common.collect.Sets;

import org.junit.After;
import org.junit.Before;
import org.junit.Test;

import com.twitter.common.base.Closure;
import com.twitter.common.net.loadbalancing.LoadBalancingStrategy.ConnectionResult;
import com.twitter.common.quantity.Amount;
import com.twitter.common.quantity.Time;
import com.twitter.common.testing.EasyMockTest;
import com.twitter.common.util.BackoffDecider;
import com.twitter.common.util.Random;
import com.twitter.common.util.TruncatedBinaryBackoff;
import com.twitter.common.util.testing.FakeClock;

/**
 * @author Krishna Gade
 */
public class MarkDeadStrategyWithHostCheckTest extends EasyMockTest {

  private static final Amount<Long, Time> INITIAL_BACKOFF = Amount.of(1L, Time.SECONDS);
  private static final Amount<Long, Time> MAX_BACKOFF = Amount.of(10L, Time.SECONDS);

  private static final String BACKEND_1 = "backend1";
  private static final String BACKEND_2 = "backend2";

  private LoadBalancingStrategy<String> wrappedStrategy;
  private Closure<Collection<String>> onBackendsChosen;

  private LoadBalancingStrategy<String> markDead;
  private Random random;
  private FakeClock clock;

  @Before
  public void setUp() {
    wrappedStrategy = createMock(new Clazz<LoadBalancingStrategy<String>>() {});
    onBackendsChosen = createMock(new Clazz<Closure<Collection<String>>>() {});

    random = createMock(Random.class);
    clock = new FakeClock();

    Function<String, BackoffDecider> backoffFactory =
        new Function<String, BackoffDecider>() {
          @Override public BackoffDecider apply(String s) {
            return BackoffDecider.builder(s)
                .withSeedSize(1)
                .withClock(clock)
                .withRandom(random)
                .withTolerateFailureRate(0.5)
                .withStrategy(new TruncatedBinaryBackoff(INITIAL_BACKOFF, MAX_BACKOFF))
                // This recovery type is suggested for load balancer strategies to prevent
                // connection pool churn that would occur from the random linear recovery type.
                .withRecoveryType(BackoffDecider.RecoveryType.FULL_CAPACITY)
                .withRequestWindow(MAX_BACKOFF)
                .build();
          }
        };

    markDead = new MarkDeadStrategyWithHostCheck<String>(wrappedStrategy, backoffFactory);

  }

  @After
  public void verify() {
    control.verify();
  }

  @Test
  public void testDeadHost() {
    wrappedStrategy.offerBackends(Sets.newHashSet(BACKEND_1, BACKEND_2), onBackendsChosen);
    expectConnected(BACKEND_1, ConnectionResult.SUCCESS, 10);
    expectConnected(BACKEND_2, ConnectionResult.SUCCESS, 4);
    expectConnected(BACKEND_2, ConnectionResult.FAILED, 4);
    wrappedStrategy.offerBackends(Sets.newHashSet(BACKEND_1), onBackendsChosen);

    expectConnected(BACKEND_2, ConnectionResult.SUCCESS, 1);
    wrappedStrategy.offerBackends(Sets.newHashSet(BACKEND_1, BACKEND_2), onBackendsChosen);

    control.replay();

    markDead.offerBackends(Sets.newHashSet(BACKEND_1, BACKEND_2), onBackendsChosen);
    connect(BACKEND_1, ConnectionResult.SUCCESS, 10);
    connect(BACKEND_2, ConnectionResult.SUCCESS, 4);
    connect(BACKEND_2, ConnectionResult.FAILED, 10);
    clock.advance(INITIAL_BACKOFF);  // Wait for backoff period to expire.
    clock.waitFor(1);
    clock.advance(INITIAL_BACKOFF);  // Wait for recovery period to expire.
    connect(BACKEND_2, ConnectionResult.SUCCESS, 1);
  }

  @Test
  public void testDeadHostWithMaxBackOff() {
    wrappedStrategy.offerBackends(Sets.newHashSet(BACKEND_1, BACKEND_2), onBackendsChosen);
    expectConnected(BACKEND_1, ConnectionResult.SUCCESS, 10);
    expectConnected(BACKEND_2, ConnectionResult.SUCCESS, 4);
    expectConnected(BACKEND_2, ConnectionResult.FAILED, 4);
    wrappedStrategy.offerBackends(Sets.newHashSet(BACKEND_1), onBackendsChosen);

    expectConnected(BACKEND_2, ConnectionResult.SUCCESS, 1);
    wrappedStrategy.offerBackends(Sets.newHashSet(BACKEND_1, BACKEND_2), onBackendsChosen);

    control.replay();

    markDead.offerBackends(Sets.newHashSet(BACKEND_1, BACKEND_2), onBackendsChosen);
    connect(BACKEND_1, ConnectionResult.SUCCESS, 10);
    connect(BACKEND_2, ConnectionResult.SUCCESS, 4);
    connect(BACKEND_2, ConnectionResult.FAILED, 10);
    clock.advance(INITIAL_BACKOFF);  // Wait for backoff period to expire.
    clock.waitFor(1);
    clock.advance(INITIAL_BACKOFF);  // Wait for recovery period to expire.
    clock.advance(MAX_BACKOFF);  // Wait for recovery period to expire.
    connect(BACKEND_2, ConnectionResult.SUCCESS, 1);
  }

  private int connect(String backend, ConnectionResult result, int count) {
    for (int i = 0; i < count; i++) {
      markDead.addConnectResult(backend, result, 0L);
    }
    return count;
  }

  private void expectConnected(String backend, ConnectionResult result, int count) {
    for (int i = 0; i < count; i++) {
      wrappedStrategy.addConnectResult(backend, result, 0L);
    }
  }
}