mariadb-galera

A Docker build file to construct a container of a MariaDB-Galera cluster node.

Steps to get a working Galera cluster:

1. Build the image. Tag it something like maria-galera. While it builds, continue up to the "Start the first node" step.

   (Mind the dot at the end of the command)

    $ sudo docker build --rm --tag=maria-galera .
   

2. Prepare conf, data, and log directories for the first node.

    $ mkdir -p /path/to/node1/conf
    $ mkdir -p /path/to/node1/data
    $ mkdir -p /path/to/node1/log
   

3. Copy the cluster.cnf to the node's conf directory.

    $ cp conf/cluster.cnf /path/to/node1/conf
   

4. Edit the cluster.cnf file, set the root password you want to use in the wsrep_sst_auth property. Make sure wsrep_cluster_address is configured to gcomm://

    $ vi /path/to/node1/conf/cluster.cnf
   

5. Start the first node passing all directories and port mappings. Give it a proper name.

   Notice how WSREP ports are mapped to the same numbers outside the container, this is because there is no way (read: "I couldn't find a way") to make WSREP listen on one port but tell its clients to connect to another.

   WSREP ports are all the ports you'll find in the cluster.cnf file: A gmcast port and SST receive port. If you happen to configure anything else whatsoever in MariaDB requiring another port, you'll have to publish it here as well.

    $ sudo docker run \
        -v /path/to/node1/conf:/conf \
        -v /path/to/node1/data:/data \
        -v /path/to/node1/log:/log \
        -p 10011:3306 \
        -p 10012:10012 \
        -p 10014:10014 \
        -d -t --name=maria1 maria-galera
   

6. Connect to the node, change the root password to the same value you specified in cluster.cnf (initial password is 1234). Also check WSREP is active (look for wsrep_ready ON) and create some test database to verify later that replication worked.

    $ mysql -p -h <ip> --protocol=TCP -P 10011 -u root
    MariaDB [(none)]> set password for 'root'@'%' = password('whatever');
    MariaDB [(none)]> set password for 'root'@'localhost' = password('whatever');
    MariaDB [(none)]> show status like 'wsrep%';
    MariaDB [(none)]> create database test;
    MariaDB [(none)]> use test
    MariaDB [test]> create table test (a int, b varchar(200), primary key(a));
    MariaDB [test]> insert into test values (1, '1');
    MariaDB [test]> \q
   

7. Create the conf, data, and log directories for all remaining nodes.

8. Copy the cluster.cnf from the first node to the conf directory of all remaining nodes, changing the wsrep_cluster_address property to gcomm://<external-ip-of-the-first-node>:<sst-port>.

   For the sample first node created above, the property would be:

    gcomm://external_ip:10012
   

9. Start all remaining nodes.

10. Connect to the last node you started with the root password you configured in the first node and check that the test database is there.

11. Edit again all cluster.cnf files and set the wsrep_cluster_address property to list all nodes in the cluster except itself. This is necessary to allow any node other than the first one you created to be the donor in case a node goes out of sync.

    The value should read something like this:

     gcomm://<ext-ip-1>:<port-1>,<ext-ip-2>:<port-2>,...,<ext-ip-N>:<port-N>
    

12. Restart nodes one by one.

     $ sudo docker restart mariaX