Examples of org.apache.zookeeper.ZooKeeper

org.apache.zookeeper.ZooKeeper
This is the main class of ZooKeeper client library. To use a ZooKeeper service, an application must first instantiate an object of ZooKeeper class. All the iterations will be done by calling the methods of ZooKeeper class.
Once a connection to a server is established, a session ID is assigned to the client. The client will send heart beats to the server periodically to keep the session valid.
The application can call ZooKeeper APIs through a client as long as the session ID of the client remains valid.
If for some reason, the client fails to send heart beats to the server for a prolonged period of time (exceeding the sessionTimeout value, for instance), the server will expire the session, and the session ID will become invalid. The client object will no longer be usable. To make ZooKeeper API calls, the application must create a new client object.
If the ZooKeeper server the client currently connects to fails or otherwise does not respond, the client will automatically try to connect to another server before its session ID expires. If successful, the application can continue to use the client.
Some successful ZooKeeper API calls can leave watches on the "data nodes" in the ZooKeeper server. Other successful ZooKeeper API calls can trigger those watches. Once a watch is triggered, an event will be delivered to the client which left the watch at the first place. Each watch can be triggered only once. Thus, up to one event will be delivered to a client for every watch it leaves.
A client needs an object of a class implementing Watcher interface for processing the events delivered to the client. When a client drops current connection and re-connects to a server, all the existing watches are considered as being triggered but the undelivered events are lost. To emulate this, the client will generate a special event to tell the event handler a connection has been dropped. This special event has type EventNone and state sKeeperStateDisconnected.

            // the removed server
            // while others are invoked by a client connected to some other
            // server.
            // when we're removing the leader, zk1 will be the client connected
            // to removed server
            ZooKeeper zk1 = (changingIndex == leaderIndex) ? zkArr[leaderIndex]
                    : zkArr[(leaderIndex % qu.ALL) + 1];


            // exactly as it is now, except for role change
            joiningServers.add("server."
                    + changingIndex

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            Thread.sleep(1000);
            zkArr[observerIndex].setData("/test", "teststr".getBytes(), -1);
          }
          Assert.fail("client port didn't change");
        } catch (KeeperException.ConnectionLossException e) {
            zkArr[observerIndex] = new ZooKeeper("127.0.0.1:"
                    + qu.getPeer(observerIndex).peer.getClientPort(),
                    ClientBase.CONNECTION_TIMEOUT, new Watcher() {
                        public void process(WatchedEvent event) {}});
        }

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        String remotePeerBean3 = CommonNames.DOMAIN
                + ":name0=ReplicatedServer_id" + replica3 + ",name1=replica."
                + leavingIndex;
        assertRemotePeerMXBeanAttributes(leavingQS3, remotePeerBean3);


        ZooKeeper zk = zkArr[leavingIndex];


        leavingServers.add(Integer.toString(leavingIndex));


        // remember this server so we can add it back later
        joiningServers.add("server." + leavingIndex + "=127.0.0.1:"

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                + changingIndex;
        assertRemotePeerMXBeanAttributes(changingQS3, remotePeerBean3);


        String newRole = "observer";


        ZooKeeper zk = zkArr[changingIndex];


        // exactly as it is now, except for role change
        joiningServers.add("server." + changingIndex + "=127.0.0.1:"
                + qu.getPeer(changingIndex).peer.getQuorumAddress().getPort()
                + ":"

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        Assert.assertTrue("waiting for server being up",
                ClientBase.waitForServerUp("127.0.0.1:" + CLIENT_PORT,
                        CONNECTION_TIMEOUT));




        ZooKeeper zk = new ZooKeeper("127.0.0.1:" + CLIENT_PORT,
                ClientBase.CONNECTION_TIMEOUT, this);


        zk.create("/foo", "foobar".getBytes(), Ids.OPEN_ACL_UNSAFE,
                CreateMode.PERSISTENT);
        Assert.assertEquals(new String(zk.getData("/foo", null, null)), "foobar");
        zk.close();


        main.shutdown();
        main.join();
        main.deleteDirs();

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        Assert.assertTrue("waiting for server being up",
                ClientBase.waitForServerUp("127.0.0.1:" + CLIENT_PORT,
                        CONNECTION_TIMEOUT));


        ZooKeeper zk = new ZooKeeper("127.0.0.1:" + CLIENT_PORT,
                ClientBase.CONNECTION_TIMEOUT, this);


        zk.create("/foo", "foobar".getBytes(), Ids.OPEN_ACL_UNSAFE,
                CreateMode.PERSISTENT);
        Assert.assertEquals(new String(zk.getData("/foo", null, null)),
                "foobar");
        zk.close();


        main.shutdown();
        main.join();
        main.deleteDirs();

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    private void verifySessionTimeOut(int sessionTimeout,
            int expectedSessionTimeout, String HOSTPORT) throws IOException,
            KeeperException, InterruptedException {
        clientConnected = new CountDownLatch(1);
        ZooKeeper zk = new ZooKeeper(HOSTPORT, sessionTimeout, this);
        Assert.assertTrue("Failed to establish zkclient connection!",
                clientConnected.await(sessionTimeout, TimeUnit.MILLISECONDS));
        Assert.assertEquals("Not able to configure the sessionTimeout values",
                expectedSessionTimeout, zk.getSessionTimeout());
        zk.close();
    }

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        f.startup(zks);
        Assert.assertTrue("waiting for server being up ", ClientBase
                .waitForServerUp(HOSTPORT, CONNECTION_TIMEOUT));


        CountdownWatcher watcher = new CountdownWatcher();
        ZooKeeper zk = new ZooKeeper(HOSTPORT, CONNECTION_TIMEOUT, watcher);
        watcher.waitForConnected(CONNECTION_TIMEOUT);


        List<String> joiners = new ArrayList<String>();
        joiners.add("server.2=localhost:1234:1235;1236");
        // generate some transactions that will get logged
        try {
            zk.reconfig(joiners, null, null, -1, new Stat());
            Assert.fail("Reconfiguration in standalone should trigger " +
                        "UnimplementedException");
        } catch (KeeperException.UnimplementedException ex) {
            // expected
        }
        zk.close();


        zks.shutdown();
        f.shutdown();
        Assert.assertTrue("waiting for server being down ", ClientBase
                .waitForServerDown(HOSTPORT, CONNECTION_TIMEOUT));

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        // Both servers 0 and 1 will have the .next config file, which means
        // for them that a reconfiguration was in progress when they failed
        // and the leader will complete it
        MainThread mt[] = new MainThread[SERVER_COUNT];
        ZooKeeper zk[] = new ZooKeeper[SERVER_COUNT];
        for (int i = 0; i < SERVER_COUNT - 1; i++) {
            mt[i] = new MainThread(i, clientPorts[i], currentQuorumCfgSection);
            // note that we should run the server, shut it down and only then
            // simulate a reconfig in progress by writing the temp file, but here no
            // other server is competing with them in FLE, so we can skip this step
            // (server 2 is booted after FLE ends)
            mt[i].writeTempDynamicConfigFile(nextQuorumCfgSection);
            mt[i].start();
            zk[i] = new ZooKeeper("127.0.0.1:" + clientPorts[i],
                    ClientBase.CONNECTION_TIMEOUT, this);
        }


        Assert.assertTrue("waiting for server 0 being up", ClientBase
                .waitForServerUp("127.0.0.1:" + clientPorts[0],
                        CONNECTION_TIMEOUT));
        Assert.assertTrue("waiting for server 1 being up", ClientBase
                .waitForServerUp("127.0.0.1:" + clientPorts[1],
                        CONNECTION_TIMEOUT));


        int leader = mt[0].main.quorumPeer.leader == null ? 1 : 0;


        // the new server's config is going to include itself and the current leader
        sb = new StringBuilder();
        sb.append(allServers.get(leader) + "\n");
        sb.append(allServers.get(2) + "\n");


        // suppose that this new server never heard about the reconfig proposal
        String newServerInitialConfig = sb.toString();
        mt[2] = new MainThread(2, clientPorts[2], newServerInitialConfig);
        mt[2].start();
        zk[2] = new ZooKeeper("127.0.0.1:" + clientPorts[2],
                ClientBase.CONNECTION_TIMEOUT, this);


        Assert.assertTrue("waiting for server 2 being up", ClientBase
                .waitForServerUp("127.0.0.1:" + clientPorts[2],
                        CONNECTION_TIMEOUT));

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        }
        sb.append("version=200000000\n"); // version of current config is 100000000
        nextQuorumCfgSection = sb.toString();


        MainThread mt[] = new MainThread[SERVER_COUNT];
        ZooKeeper zk[] = new ZooKeeper[SERVER_COUNT];


        // run servers 0 and 1 normally
        for (int i = 0; i < 2; i++) {
            mt[i] = new MainThread(i, oldClientPorts[i],
                    currentQuorumCfgSection);
            mt[i].start();
            zk[i] = new ZooKeeper("127.0.0.1:" + oldClientPorts[i],
                    ClientBase.CONNECTION_TIMEOUT, this);
        }


        for (int i = 0; i < 2; i++) {
            Assert.assertTrue("waiting for server " + i + " being up",
                    ClientBase.waitForServerUp(
                            "127.0.0.1:" + oldClientPorts[i],
                            CONNECTION_TIMEOUT * 2));
        }


        ReconfigTest.testNormalOperation(zk[0], zk[1]);


        // shut them down and then simulate a reboot with a reconfig in progress
        for (int i = 0; i < 2; i++) {
            mt[i].shutdown();
            zk[i].close();
        }


        for (int i = 0; i < 2; i++) {
            Assert.assertTrue(
                    "waiting for server " + i + " being up",
                    ClientBase.waitForServerDown("127.0.0.1:"
                            + oldClientPorts[i], CONNECTION_TIMEOUT * 2));
        }


        for (int i = 0; i < 2; i++) {
            mt[i].writeTempDynamicConfigFile(nextQuorumCfgSection);
            mt[i].start();
            zk[i] = new ZooKeeper("127.0.0.1:" + clientPorts[i],
                    ClientBase.CONNECTION_TIMEOUT, this);
        }


        // new members are initialized with current config + the new server
        for (int i = 2; i < SERVER_COUNT; i++) {
            mt[i] = new MainThread(i, clientPorts[i], currentQuorumCfg
                    + allServersNext.get(i));
            mt[i].start();
            zk[i] = new ZooKeeper("127.0.0.1:" + clientPorts[i],
                    ClientBase.CONNECTION_TIMEOUT, this);
        }


        for (int i = 0; i < SERVER_COUNT; i++) {
            Assert.assertTrue("waiting for server " + i + " being up",

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