com.netflix.curator.test.KillSession.java Source code

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Here is the source code for com.netflix.curator.test.KillSession.java

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/*
 *
 *  Copyright 2011 Netflix, Inc.
 *
 *     Licensed 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 com.netflix.curator.test;

import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.ZooKeeper;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.TimeUnit;

/**
 * <p>
 *     Utility to simulate a ZK session dying. See: <a href="http://wiki.apache.org/hadoop/ZooKeeper/FAQ#A4">ZooKeeper FAQ</a>
 * </p>
 *
 * <blockquote>
 *     In the case of testing we want to cause a problem, so to explicitly expire a session an
 *     application connects to ZooKeeper, saves the session id and password, creates another
 *     ZooKeeper handle with that id and password, and then closes the new handle. Since both
 *     handles reference the same session, the close on second handle will invalidate the session
 *     causing a SESSION_EXPIRED on the first handle.
 * </blockquote>
 */
public class KillSession {
    /**
     * Kill the given ZK session
     *
     * @param client the client to kill
     * @param connectString server connection string
     * @throws Exception errors
     */
    public static void kill(ZooKeeper client, String connectString) throws Exception {
        kill(client, connectString, new Timing().forWaiting().milliseconds());
    }

    /**
     * Kill the given ZK session
     *
     * @param client the client to kill
     * @param connectString server connection string
     * @param maxMs max time ms to wait for kill
     * @throws Exception errors
     */
    public static void kill(ZooKeeper client, String connectString, int maxMs) throws Exception {
        long startTicks = System.currentTimeMillis();

        final CountDownLatch sessionLostLatch = new CountDownLatch(1);
        Watcher sessionLostWatch = new Watcher() {
            @Override
            public void process(WatchedEvent event) {
                sessionLostLatch.countDown();
            }
        };
        client.exists("/___CURATOR_KILL_SESSION___" + System.nanoTime(), sessionLostWatch);

        final CountDownLatch connectionLatch = new CountDownLatch(1);
        Watcher connectionWatcher = new Watcher() {
            @Override
            public void process(WatchedEvent event) {
                if (event.getState() == Event.KeeperState.SyncConnected) {
                    connectionLatch.countDown();
                }
            }
        };
        ZooKeeper zk = new ZooKeeper(connectString, maxMs, connectionWatcher, client.getSessionId(),
                client.getSessionPasswd());
        try {
            if (!connectionLatch.await(maxMs, TimeUnit.MILLISECONDS)) {
                throw new Exception("KillSession could not establish duplicate session");
            }
            try {
                zk.close();
            } finally {
                zk = null;
            }

            while (client.getState().isConnected() && !sessionLostLatch.await(100, TimeUnit.MILLISECONDS)) {
                long elapsed = System.currentTimeMillis() - startTicks;
                if (elapsed > maxMs) {
                    throw new Exception("KillSession timed out waiting for session to expire");
                }
            }
        } finally {
            if (zk != null) {
                zk.close();
            }
        }
    }
}