Create a ZooKeeper ensemble

This section describes the creation of a ZooKeeper ensemble with servers located on different hosts. The following example shows an ensemble comprised of three instances, follow these instructions:

• Launch as much ZooKeeper instances as nodes you want to have in the ensemble. (In this example, three instances).

• Check that the value of the /opt/bitnami/zookeeper/data/myid file is equal to 1.

• Edit the /opt/bitnami/zookeeper/conf/zoo.cfg file to add the following content. Remember to replace IP_ADDRESS with the corresponding IP address of each instance.

    server.1=IP_ADDRESS_SERVER1:2888:3888
    server.2=IP_ADDRESS_SERVER2:2888:3888
    server.3=IP_ADDRESS_SERVER3:2888:3888
  

• Restart ZooKeeper services:

    $ sudo /opt/bitnami/ctlscript.sh restart zookeeper
  

Configuring the second ZooKeeper instance

• Edit the /opt/bitnami/zookeeper/data/myid file and change the value 1 to 2.

• Edit the /opt/bitnami/zookeeper/conf/zoo.cfg file to add the following content. Remember to replace IP_ADDRESS with the corresponding IP address of each instance.

    server.1=IP_ADDRESS_SERVER1:2888:3888
    server.2=IP_ADDRESS_SERVER2:2888:3888
    server.3=IP_ADDRESS_SERVER3:2888:3888
  

• Restart ZooKeeper services:

    $ sudo /opt/bitnami/ctlscript.sh restart zookeeper
  

Configuring the third ZooKeeper instance

• Edit the /opt/bitnami/zookeeper/data/myid file and change the value 1 to 3.

• Edit the /opt/bitnami/zookeeper/conf/zoo.cfg file to add the following content. Remember to replace IP_ADDRESS with the corresponding IP address of each instance.

    server.1=IP_ADDRESS_SERVER1:2888:3888
    server.2=IP_ADDRESS_SERVER2:2888:3888
    server.3=IP_ADDRESS_SERVER3:2888:3888
  

• Restart ZooKeeper services:

    $ sudo /opt/bitnami/ctlscript.sh restart zookeeper
  

Testing the ensemble

To check if the replication is working correctly in the cluster, let’s try the following:

• In the server 1, connect to ZooKeeper by executing the following:

    $ zkCli.sh
  

• Create a new directory named ensemble with a string named test using the create / command. This creates a new znode and associates the string test with the node. You should see:

    $ create /ensemble test
    Created /ensemble
  

• Use the list command again to see how the directory looks like now:

    $ ls /
    [zookeeper, ensemble]
  

• Go to the server 2 and connect to ZooKeeper using the zkCli.sh command.

• Use the ls / command to check that you have the same data in both instances. You should see the same output you have obtained in the server 1 when executing that command:

    $ ls /
    [zookeeper, ensemble]
  

Congratulations! You now have a ZooKeeper ensemble running and ready to replicate the data through all the instances/nodes.