Ansible role for installing and configuring Apache ZooKeeper

This role can be used to install and cluster multiple ZooKeeper nodes, this uses all hosts defined for the "zookeeper-nodes" group in the inventory file by default. All servers are added to the zoo.cfg file along with the leader and election ports.

• Debian 10.x
• RedHat 7
• RedHat 8
• Ubuntu 18.04.x
• Ubuntu 20.04.x

Java: Java 8 / 11

Ansible 2.9.16 or 2.10.4 are the minimum required versions to workaround an issue with certain kernels that have broken the systemd status check. The error message "Service is in unknown state" will be output when attempting to start the service via the Ansible role and the task will fail. The service will start as expected if the systemctl start command is run on the physical host. See ansible/ansible#71528 for more information.

• The ZooKeeper service can be started via: systemctl start zookeeper
• The ZooKeeper service can be stopped via: systemctl stop zookeeper

ZooKeeper can use commands based on four letter words, see https://zookeeper.apache.org/doc/current/zookeeperAdmin.html#sc_4lw

The below example uses the stat command to find out which instance is the leader :

for i in 1 2 3 ; do
  echo "zookeeper0$i is a "$(echo stat | nc zookeeper0$i 2181 | grep ^Mode | awk '{print $2}');
done

No dependencies

- hosts: zookeeper-nodes
  roles:
    - sleighzy.zookeeper

Linting should be done using ansible-lint

pip3 install ansible-lint --user

This module uses the Ansible Molecule testing framework. This test suite creates a ZooKeeper cluster consisting of three nodes running within Docker containers. Each container runs a different OS to test the supported platforms for this Ansible role.

As per the [Molecule Installation guide] this should be done using a virtual environment. The commands below will create a Python virtual environment and install Molecule including the Docker driver.

Note: Due to a breaking change in Molecule 3.1.1 the Docker driver for Molecule has been removed and the molecule-driver module must be installed separately.

$ python3 -m venv molecule-venv
$ source molecule-venv/bin/activate
(molecule-venv) $ python3 -m pip install ansible ansible-lint yamllint docker molecule-docker "molecule[docker,lint]"

Run playbook and tests. Linting errors need to be corrected before Molecule will execute any tests. This will run all tests and then destroy the Docker containers.

molecule test

The below command can be used to run the playbook without the tests. This can be run multiple times when making changes to the role, and ensuring that operations are idempotent.

molecule converge

The below commands can be used to just run the tests without tearing everything down. The command molecule verify can be repeated for each test run.

molecule create
molecule converge
molecule verify

Tear down Molecule tests and Docker containers.

molecule destroy