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 >= 2.0 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