curator-master/curator-x-discovery/src/test/java/org/apache/curator/x/discovery/details/TestServiceCacheRace.java
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 * distributed with this work for additional information
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 * 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
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package org.apache.curator.x.discovery.details;

import static org.junit.jupiter.api.Assertions.assertTrue;
import com.google.common.collect.Lists;
import java.io.Closeable;
import java.util.Collections;
import java.util.List;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.Executors;
import org.apache.curator.framework.CuratorFramework;
import org.apache.curator.framework.CuratorFrameworkFactory;
import org.apache.curator.framework.state.ConnectionState;
import org.apache.curator.retry.RetryOneTime;
import org.apache.curator.test.BaseClassForTests;
import org.apache.curator.test.Timing;
import org.apache.curator.test.compatibility.CuratorTestBase;
import org.apache.curator.utils.CloseableExecutorService;
import org.apache.curator.utils.CloseableUtils;
import org.apache.curator.x.discovery.ServiceCache;
import org.apache.curator.x.discovery.ServiceDiscovery;
import org.apache.curator.x.discovery.ServiceDiscoveryBuilder;
import org.apache.curator.x.discovery.ServiceInstance;
import org.junit.jupiter.api.Tag;
import org.junit.jupiter.api.Test;
import org.slf4j.LoggerFactory;

@Tag(CuratorTestBase.zk35TestCompatibilityGroup)
public class TestServiceCacheRace extends BaseClassForTests {
    private final Timing timing = new Timing();

    // validates CURATOR-452 which exposed a race in ServiceCacheImpl's start() method caused by an optimization whereby
    // it clears the dataBytes of its internal PathChildrenCache
    @Test
    public void testRaceOnInitialLoad() throws Exception {
        List<Closeable> closeables = Lists.newArrayList();
        try {
            CuratorFramework client = CuratorFrameworkFactory.newClient(server.getConnectString(), new RetryOneTime(1));
            closeables.add(client);
            client.start();

            ServiceDiscovery<String> discovery = ServiceDiscoveryBuilder.builder(String.class)
                    .basePath("/discovery")
                    .client(client)
                    .build();
            closeables.add(discovery);
            discovery.start();

            CountDownLatch cacheStartLatch = new CountDownLatch(1);
            CountDownLatch cacheWaitLatch = new CountDownLatch(1);
            final ServiceCache<String> cache =
                    discovery.serviceCacheBuilder().name("test").build();
            closeables.add(cache);
            ((ServiceCacheImpl) cache).debugStartLatch =
                    cacheStartLatch; // causes ServiceCacheImpl.start to notify just after starting its internal
            // PathChildrenCache
            ((ServiceCacheImpl) cache).debugStartWaitLatch =
                    cacheWaitLatch; // causes ServiceCacheImpl.start to wait before iterating over its internal
            // PathChildrenCache

            ServiceInstance<String> instance1 = ServiceInstance.<String>builder()
                    .payload("test")
                    .name("test")
                    .port(10064)
                    .build();
            discovery.registerService(instance1);

            CloseableExecutorService closeableExecutorService =
                    new CloseableExecutorService(Executors.newSingleThreadExecutor());
            closeables.add(closeableExecutorService);
            final CountDownLatch startCompletedLatch = new CountDownLatch(1);
            Runnable proc = new Runnable() {
                @Override
                public void run() {
                    try {
                        cache.start();
                        startCompletedLatch.countDown();
                    } catch (Exception e) {
                        LoggerFactory.getLogger(getClass()).error("Start failed", e);
                        throw new RuntimeException(e);
                    }
                }
            };
            closeableExecutorService.submit(proc);
            assertTrue(timing.awaitLatch(
                    cacheStartLatch)); // wait until ServiceCacheImpl's internal PathChildrenCache is started and primed

            final CountDownLatch cacheChangedLatch = new CountDownLatch(1);
            ServiceCacheListener listener = new ServiceCacheListener() {
                @Override
                public void cacheChanged() {
                    cacheChangedLatch.countDown();
                }

                @Override
                public void stateChanged(CuratorFramework client, ConnectionState newState) {
                    // NOP
                }
            };
            cache.addListener(listener);
            ServiceInstance<String> instance2 = ServiceInstance.<String>builder()
                    .payload("test")
                    .name("test")
                    .port(10065)
                    .build();
            discovery.registerService(
                    instance2); // cause ServiceCacheImpl's internal PathChildrenCache listener to get called which will
            // clear the dataBytes
            assertTrue(timing.awaitLatch(cacheChangedLatch));

            cacheWaitLatch.countDown();

            assertTrue(timing.awaitLatch(startCompletedLatch));
        } finally {
            Collections.reverse(closeables);
            for (Closeable c : closeables) {
                CloseableUtils.closeQuietly(c);
            }
        }
    }
}
