src/test/java/org/apache/sling/distribution/journal/impl/shared/ExponentialBackoffTest.java

/*
 * 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
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 */
package org.apache.sling.distribution.journal.impl.shared;

import static java.time.temporal.ChronoUnit.MILLIS;
import static org.hamcrest.CoreMatchers.equalTo;
import static org.junit.Assert.assertThat;

import java.time.Duration;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.TimeUnit;

import org.junit.Test;
import org.junit.runner.RunWith;
import org.mockito.runners.MockitoJUnitRunner;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

@RunWith(MockitoJUnitRunner.class)
public class ExponentialBackoffTest {
    private static final int RETRIES = 5;
    private static final Duration INITIAL_DELAY = Duration.of(64, MILLIS);
    private static final Duration MAX_DELAY = Duration.of(256, MILLIS);
    
    private Logger log = LoggerFactory.getLogger(this.getClass());
    
    private volatile CountDownLatch countDown = new CountDownLatch(RETRIES);
    
    @Test
    public void testRetries() throws Exception {
        
        log.info("Checking exponentional backoff");
        ExponentialBackOff backOff = new ExponentialBackOff(INITIAL_DELAY, MAX_DELAY, false, this::checkCallback);
        backOff.startChecks();
        // Run into double trigger protection
        backOff.startChecks();
        boolean finished = this.countDown.await(MAX_DELAY.toMillis() * RETRIES, TimeUnit.MILLISECONDS);
        assertThat("Should finish before the timeout", finished, equalTo(true));

        log.info("Checking for long delay if next error happens quickly");
        this.countDown = new CountDownLatch(1);
        backOff.startChecks();
        boolean finished2 = this.countDown.await(INITIAL_DELAY.toMillis() * 2, TimeUnit.MILLISECONDS);
        assertThat("Should not finish quickly as we called startChecks immediately", finished2, equalTo(false));
        this.countDown.await();

        log.info("Checking for short delay if next error happens after enough time");
        Thread.sleep(MAX_DELAY.toMillis() * 3);
        this.countDown = new CountDownLatch(1);
        backOff.startChecks();
        boolean finished3 = this.countDown.await(INITIAL_DELAY.toMillis() * 4, TimeUnit.MILLISECONDS);
        assertThat("Should finish quickly as we called startChecks after enough delay", finished3, equalTo(true));

        backOff.close();
        
    }
    
    private void checkCallback() {
        this.countDown.countDown();
        if (countDown.getCount() > 0) {
            throw new RuntimeException("Failing num: " + this.countDown.getCount());
        }
    }
}