sadpdtchr / mariadb-ansible-galera-cluster

Automated installation of MariaDB Galera Cluster using Ansible

configuration management for MariaDB Galera cluster

These roles allow you to automatically setup a MariaDB Galera cluster with sane default settings.

These roles are currently only tested for RHEL/CentOS 7, but most tasks can be reused for Debian or SUSE based distributions.

Prerequisites

The machine from which the playbook is being run needs to have Ansible >= 2.5 installed. For detailed information how to obtain current packages for your distribution of choice have a look at the Ansible documentation.

As we're accessing information from a group of hosts within these playbooks we need to have fact caching enabled in Ansible. To, for example, cache using json files in you homedirectory you would add the following lines to /etc/ansible/ansible.cfg:

[defaults]
gathering = smart
fact_caching = jsonfile
fact_caching_connection = ~/.ansible/cache

For more information about other cache mechanisms have a look at the Ansible documentation regarding fact-caching.

Installing requirements

To install the required packages and configure SELinux and the firewall you can run only the tasks tagged with setup

ansible-playbook -i galera.hosts galera.yml --tags setup

Configure MariaDB Galera cluster

To run all further tasks to configure MariaDB Galera cluster and add the required user for the State Snapshot Transfer (SST) either skip the tasks tagged setup or run the tags config or auth directly.

ansible-playbook -i galera.hosts galera.yml --skip-tags setup

Bootstrapping MariaDB Galera cluster

Bootstrapping the cluster can be done using a playbook dedicated for bootstrapping the MariaDB Galera cluster called galera_bootstrap.yml

ansible-playbook -i galera.hosts galera_bootstrap.yml

It uses the first node in the group galera_cluster to bootstrap the cluster.

Rolling MariaDB Galera cluster updates

The role galera_conf is set up to allow rolling updates of the configuration of the Galera cluster. When the variable bootstrapped is set to yes the mariadb service is restarted after a change of the configuration. It is important to note that the playbook contains the keyword serial: 1, meaning that the configuration is applied one node at a time so that the will never lose quorum in the process of applying the new configuration.

ansible-playbook -i galera.hosts galera_rolling_update.yml

Vagrant support

For the live demo during the presentation I've been using Vagrant and with the following instructions you can use the Vagrantfile to perform those steps.

Prerequisites

As we need support for Vagrant private_network we need Guest Additions installed in the guest OS. The vagrant-vbguest plugins automatically takes care of this.

vagrant plugin install vagrant-vbguest

Vagrant setup

By running vagrant up all Ansible tasks in the galera.yml playbook will be run. To bootstrap the cluster afterwards a separate run of the galera_bootstrap.yml playbook is required.

PYTHONUNBUFFERED=1 ANSIBLE_FORCE_COLOR=true ANSIBLE_HOST_KEY_CHECKING=false ANSIBLE_SSH_ARGS='-o UserKnownHostsFile=/dev/null -o IdentitiesOnly=yes -o ControlMaster=auto -o ControlPersist=60s' ansible-playbook --connection=ssh --inventory-file=.vagrant/provisioners/ansible/inventory --sudo galera_bootstrap.yml