In this article, I will take you through Zookeeper Installation on Ubuntu 18.04. Zookeeper is an external software used to track information that must be synchronized across your cluster. In a Real world Distributed System, Cluster might get into any kind of Failures like individual nodes went down, time drift between the nodes, network go down etc. To handle these kind of situations Zookeeper is the perfect tool which sits off your side and manage all this overhead for you.

In this article, you will learn about following topics:-

• Zookeeper Architecture
• What is Zookeeper
• How Zookeeper Leader Election Works
• Zookeeper Requirements
• Zookeeper Hostname Set Up
• Apache Zookeeper Download
• Create Server Id for Zookeeper Cluster
• Start Zookeeper Software
• Verify Zookeeper Configuration

Zookeeper Architecture 

Before going through above, let’s go through few Zookeeper Software Terminologies:-

Node: It could be any Ubuntu system running under Zookeeper cluster.

Master: A node which will be elected to perform Leader operations like assign tasks to worker nodes, recover from any partial failures etc.

Worker: A nodes which will follow the leader and will perform all the tasks given by the Leader.

Server: A node in Zookeeper ensemble which provides services to the client along with the acknowledgement that it is alive and running fine.

Client: A node in Zookeeper ensemble which connects with the Server and provides acknowledgement that it is up and running fine.

 

Install Apache Zookeeper

Before going through the steps to install Zookeeper, check Zookeeper requirements, perform Zookeeper download in all 3 nodes, setup Zookeeper configuration and start Zookeeper Cluster we first need to understand What is Zookeeper.

Also Read: How to install Perl on CentOS 7

What is Zookeeper

Zookeeper is a tool which applications can use to recover from partial failures. It keeps track of Master node, worker nodes, workers tasks and facilitate data synchronization across your cluster. It is an integral part of Applications like HBase, Kafka, Drill, Storm and many more.

How Zookeeper Leader Election Works

One node register itself as master and put a lock on it. Other nodes in the cluster cannot become master till this lock get released from the elected master. This lock also prevents to create multiple master within a Cluster.

Step 1: Zookeeper Requirements

a)You need to have 3 Ubuntu running Nodes.

b)Update your system

[root@znode1 ~]# apt-get update

c)Make sure java is installed

[root@znode1 ~]# java -version

d)You need to have an user with sudo access.

Step 2: Set up Hostname

You need to first set up your hostname in all the 3 nodes.

Node 1:-

root@znode1:~#hostnamectl set-hostname znode1
root@znode1:~#exec bash
root@znode1:~#vi /etc/hosts

192.168.0.106 znode1
192.168.0.105 znode2
192.168.0.110 znode3

Node 2:-

root@znode1:~#hostnamectl set-hostname znode2
root@znode1:~#exec bash
root@znode1:~#vi /etc/hosts

192.168.0.106 znode1
192.168.0.105 znode2
192.168.0.110 znode3

Node 3:-

root@znode1:~#hostnamectl set-hostname znode3
root@znode1:~#exec bash
root@znode1:~#vi /etc/hosts

192.168.0.106 znode1
192.168.0.105 znode2
192.168.0.110 znode3

Step 3: Apache Zookeeper Download

Download Apache Zookeeper using wget in all 3 nodes. At the time of writing, Zookeeper-3.5.6 is the Latest Release. You can choose the latest release from Zookeeper website as per your requirement.

Node 1:-

root@znode1:~# wget https://archive.apache.org/dist/zookeeper/zookeeper-3.5.6/apache-zookeeper-3.5.6.tar.gz
--2019-12-31 23:43:53-- https://archive.apache.org/dist/zookeeper/zookeeper-3.5.6/apache-zookeeper-3.5.6.tar.gz
Resolving archive.apache.org (archive.apache.org)... 163.172.17.199
Connecting to archive.apache.org (archive.apache.org)|163.172.17.199|:443... connected.
HTTP request sent, awaiting response... 200 OK
Length: 3132621 (3.0M) [application/x-gzip]
Saving to: ‘apache-zookeeper-3.5.6.tar.gz’

apache-zookeeper-3.5.6.tar.gz 100%[=====================================================================================>] 2.99M 333KB/s in 9.6s

2019-12-31 23:44:03 (318 KB/s) - ‘apache-zookeeper-3.5.6.tar.gz’ saved [3132621/3132621]

Node 2:-

root@znode1:~# wget https://archive.apache.org/dist/zookeeper/zookeeper-3.5.6/apache-zookeeper-3.5.6.tar.gz
--2019-12-31 23:43:53-- https://archive.apache.org/dist/zookeeper/zookeeper-3.5.6/apache-zookeeper-3.5.6.tar.gz
Resolving archive.apache.org (archive.apache.org)... 163.172.17.199
Connecting to archive.apache.org (archive.apache.org)|163.172.17.199|:443... connected.
HTTP request sent, awaiting response... 200 OK
Length: 3132621 (3.0M) [application/x-gzip]
Saving to: ‘apache-zookeeper-3.5.6.tar.gz’

apache-zookeeper-3.5.6.tar.gz 100%[=====================================================================================>] 2.99M 333KB/s in 9.6s

2019-12-31 23:44:03 (318 KB/s) - ‘apache-zookeeper-3.5.6.tar.gz’ saved [3132621/3132621]

Node 3:-

root@znode1:~# wget https://archive.apache.org/dist/zookeeper/zookeeper-3.5.6/apache-zookeeper-3.5.6.tar.gz
--2019-12-31 23:43:53-- https://archive.apache.org/dist/zookeeper/zookeeper-3.5.6/apache-zookeeper-3.5.6.tar.gz
Resolving archive.apache.org (archive.apache.org)... 163.172.17.199
Connecting to archive.apache.org (archive.apache.org)|163.172.17.199|:443... connected.
HTTP request sent, awaiting response... 200 OK
Length: 3132621 (3.0M) [application/x-gzip]
Saving to: ‘apache-zookeeper-3.5.6.tar.gz’

apache-zookeeper-3.5.6.tar.gz 100%[=====================================================================================>] 2.99M 333KB/s in 9.6s

2019-12-31 23:44:03 (318 KB/s) - ‘apache-zookeeper-3.5.6.tar.gz’ saved [3132621/3132621]

Step 4: Create an User

You need to create an user first to run all zookeeper commands.

Node 1:-

root@znode1:~# useradd -m zookeeper

Node 2:-

root@znode2:~# useradd -m zookeeper

Node 3:-

root@znode3:~# useradd -m zookeeper

Step 5: Extract Tar Files

Once downloaded, Go to /home/zookeeper directory and extract tar files in all the 3 nodes.

Node 1:-

root@znode1:~# cd /home/zookeeper/
root@znode1:~#chown zookeeper:zookeeper apache-zookeeper-3.5.6.tar.gz
zookeeper@znode1:~$ tar -xvf apache-zookeeper-3.5.6.tar.gz

Node 2:-

root@znode2:~# cd /home/zookeeper/
root@znode2:~#chown zookeeper:zookeeper apache-zookeeper-3.5.6.tar.gz
zookeeper@znode2:~$ tar -xvf apache-zookeeper-3.5.6.tar.gz

Node 3:-

root@znode3:~# cd /home/zookeeper/
root@znode3:~#chown zookeeper:zookeeper apache-zookeeper-3.5.6.tar.gz
zookeeper@znode3:~$ tar -xvf apache-zookeeper-3.5.6.tar.gz

Step 6: Create Data Directory for Zookeeper Software

Node 1:-

[zookeeper@znode1 zookeeper]#mkdir /var/lib/zookeeper;mkdir /var/log/zookeeper

Node 2:-

[zookeeper@znode2 zookeeper]#mkdir /var/lib/zookeeper;mkdir /var/log/zookeeper

Node 3:-

[zookeeper@znode3 zookeeper]#mkdir /var/lib/zookeeper;mkdir /var/log/zookeeper

Step 7: Create Server Id for Zookeeper Cluster

Here you need to create Server Id for Zookeeper cluster nodes. It could be any number between 1 and 255.

Node 1:-

zookeeper@znode1:/home/zookeeper$ echo '1' > /var/lib/zookeeper/myid

Node 2:-

zookeeper@znode2:/home/zookeeper$ echo '2' > /var/lib/zookeeper/myid

Node 3:-

zookeeper@znode3:/home/zookeeper$ echo '3' > /var/lib/zookeeper/myid

Step 8: Apache Zookeeper Configuration

Node 1:-

You will find zoo_sample.cfg configuration file under conf/ directory. You need to copy this configuration in zoo.cfg and do the necessary changes as given below:-

zookeeper@znode1:/home/zookeeper$ cd /home/zookeeper/apache-zookeeper-3.5.6/conf/
zookeeper@znode1:/home/zookeeper/apache-zookeeper-3.5.6/conf$ cp zoo_sample.cfg zoo.cfg
zookeeper@znode1:/home/zookeeper/apache-zookeeper-3.5.6/conf$vi zoo.cfg

dataDir=/var/lib/zookeeper
server.1=znode1:2888:3888
server.2=znode2:2888:3888
server.3=znode3:2888:3888

You will find another file called log4j.properties under conf/ directory. Here you need to provide the log file path where zookeeper.log will be generated.

zookeeper@znode1:/home/zookeeper/apache-zookeeper-3.5.6/conf$vi log4j.properties

zookeeper.log.dir=/var/log/zookeeper

Node 2:-

In Node 2 also, you need to do the same thing as above.

zookeeper@znode1:/home/zookeeper$ cd /home/zookeeper/apache-zookeeper-3.5.6/conf/
zookeeper@znode1:/home/zookeeper/apache-zookeeper-3.5.6/conf$ cp zoo_sample.cfg zoo.cfg
zookeeper@znode1:/home/zookeeper/apache-zookeeper-3.5.6/conf$cat zoo.cfg

dataDir=/var/lib/zookeeper
server.1=znode1:2888:3888
server.2=znode2:2888:3888
server.3=znode3:2888:3888

Configure log4j.properties here also and point the log file directory to /var/log/zookeeper

zookeeper@znode1:/home/zookeeper/apache-zookeeper-3.5.6/conf$vi log4j.properties

zookeeper.log.dir=/var/log/zookeeper

Node 3:-

Similarly perform the same steps in Node 3 as well.

zookeeper@znode1:/home/zookeeper$ cd /home/zookeeper/apache-zookeeper-3.5.6/conf/
zookeeper@znode1:/home/zookeeper/apache-zookeeper-3.5.6/conf$ cp zoo_sample.cfg zoo.cfg
zookeeper@znode1:/home/zookeeper/apache-zookeeper-3.5.6/conf$cat zoo.cfg

dataDir=/var/lib/zookeeper
server.1=znode1:2888:3888
server.2=znode2:2888:3888
server.3=znode3:2888:3888

Also set the log file directory as set in above nodes.

zookeeper@znode1:/home/zookeeper/apache-zookeeper-3.5.6/conf$vi log4j.properties

zookeeper.log.dir=/var/log/zookeeper

Step 9: Start Apache Zookeeper 

Once configuration is completed, let’s start the Zookeeper service through zkServer.sh start command.

Node 1:-

[zookeeper@znode1 data]$ /home/zookeeper/apache-zookeeper-3.5.6/bin/zkServer.sh start
/usr/bin/java
ZooKeeper JMX enabled by default
Using config: /home/zookeeper/apache-zookeeper-3.5.6/bin/../conf/zoo.cfg
Starting zookeeper ... STARTED

Node 2:-

[zookeeper@znode2 data]$ /home/zookeeper/apache-zookeeper-3.5.6/bin/zkServer.sh start
/usr/bin/java
ZooKeeper JMX enabled by default
Using config: /home/zookeeper/apache-zookeeper-3.5.6/bin/../conf/zoo.cfg
Starting zookeeper ... STARTED

Node 3:-

[zookeeper@znode3 ~]$ /home/zookeeper/apache-zookeeper-3.5.6/bin/zkServer.sh start
/usr/bin/java
ZooKeeper JMX enabled by default
Using config: /home/zookeeper/apache-zookeeper-3.5.6/bin/../conf/zoo.cfg
Starting zookeeper ... STARTED

Step 10: Verify the configuration

Once you are done through the steps to install Zookeeper, you need to validate your zookeeper configuration in all the 3 nodes. You can verify the Zookeeper configuration by running /home/zookeeper/apache-zookeeper-3.5.6/bin/zkServer.sh start-foreground command. It is very important to verify if Zookeeper Cluster configuration is working as expected or not.

Node 1:-

[zookeeper@znode1 conf]$ /home/zookeeper/apache-zookeeper-3.5.6/bin/zkServer.sh status
/bin/java
ZooKeeper JMX enabled by default
Using config: /home/zookeeper/apache-zookeeper-3.5.6/bin/../conf/zoo.cfg
Mode: follower

Node 2:-

[zookeeper@znode2 conf]$ /home/zookeeper/apache-zookeeper-3.5.6/bin/zkServer.sh status
/bin/java
ZooKeeper JMX enabled by default
Using config: /home/zookeeper/apache-zookeeper-3.5.6/bin/../conf/zoo.cfg
Mode: leader

Node 3:-

[zookeeper@znode3 conf]$ /home/zookeeper/apache-zookeeper-3.5.6/bin/zkServer.sh status
/bin/java
ZooKeeper JMX enabled by default
Using config: /home/zookeeper/apache-zookeeper-3.5.6/bin/../conf/zoo.cfg
Mode: follower

References: How to disable Transparent Huge Page