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Training Video Exercises

Installing a Galera Cluster on AWS

These exercises are part of the training video, Installing a Galera Cluster on AWS. They correspond to what is presented, and should be done after each section is viewed, unless otherwise noted.

Before starting these exercises, make sure you have all of the requirements and preparations in place.

Requirements & Preparation

  • AWS account with access to the EC2 console.

Student Materials

Before starting an exercise, read it fully and carefully. The headings for each set of exercises corresponds to the section with the same name in the training video. Make notes for yourself, after successfully performing each exercise, for when you have to do these tasks later for yourself.

Creating AWS Instances

Do these exercises after viewing the first three sections of the training video: Galera Cluster Overview, Encryption Key, and Creating AWS Instances. Don’t install any software or configure the nodes, yet.

  1. Generate an encryption key for accessing nodes. Then log into AWS and create three instances with a distribution of Linux you prefer.
  2. Create a security group to use with your instances. Add rules to allow traffic among them, using their internal IP addresses. Open TCP ports 22, 3306, 4444, 4567, and 4568 for each node. Also open UDP port 4567 for each.

Installing Software on Nodes

Do these exercises after viewing Installing Software on Nodes on the training video. Don’t configure the nodes until the next section.

  1. If you prefer to use MySQL, use a web browser to go to Codership’s web site (see links in margin) to get the URL’s for the latest wsrep-MySQL and the Galera Cluster packages. Use a text editor to create a repository file on each node and include the URLs you copied. See the margin for links to the Codership’s documentation page which shows how to construct a repository file. If you prefer to use MariaDB, go to The MariaDB Foundation page to construct a repository file based on the Linux distribution and version you’re using. Get at least version 10.4 of MariaDB.
  2. Install MySQL or MariaDB, and Galera on each node. When finished, start mysqld on each node—don’t bootstrap Galera. For MySQL, grep the MySQL log for root’s temporary password. For MariaDB, there is no password, initially. Run mysql_secure_install on each node and change the root password, as well as respond to the other questions it asks. Then try logging into MySQL or MariaDB with the mysql client as root with the new password. Exit and shutdown mysqld.

Configuring Nodes & Opening Ports

Do these exercises after viewing the two sections related to this combined title. MySQL or MariaB should be down on each node; don’t start mysqld again until the next section.

  1. Edit the database configuration file to include settings needed for Galera Cluster. There’s a link at the top under Student Materials for an example configuration file. Don’t start mysqld yet. Configure each node before proceeding to the next exercise.
  2. Configure either SELinux or Firewalld or both to open the following ports: TCP 22, TCP 3306. TCP 4444, TCP & UDP 4567, and TCP 4568. If you want to use only SELinux or only Firewalld, disable the one not used.

Starting Galera

This is the core of the training video. You may encounter problems as you do these exercises. Don’t let it frustrate you, but don’t stop trying to complete them. This is important. Keep at it until you’re able to do them.

  1. Choose a node to be the seed node—anyone will be fine. Start MySQL and Galera on the one node by using the mysqld_bootstrap script. If you’re using MariaDB, start it with Galera by using the galera_new_cluster script. If there are any errors, shutdown mysqld and read the full error messages, as well as look through the database log for clues. Resolve any problems and keep trying until you get it started. Then execute SHOW STATUS with the LIKE operator to see if Galera is running.
  2. Once you have the first node running MySQL or MariaDB, and Galera, start mysqld on one of the other nodes—don’t use the mysqld_bootstrap and galera_new_cluster scripts. If there are any errors, shutdown mysqld and resolve them until you get it started. Execute the SHOW STATUS statement with the LIKE operator to see the wsrep_cluster_size. It should have a value of 2.
  3. Download the dump file containing the company database (see link at the top under Student Materials) onto the first node. There’s one for MySQL and another for MariaDB: use the one that matches your database system. Both were created with mysqldump, so use the mysql client to load the data. When it’s finished, check the second node to see if it replicated the data.
  4. Start mysqld on the third node. After it has successfully joined the cluster, look to see if it has replicated the company database. Enter the CREATE DATABASE statement to create a database without tables. Check that the other nodes replicated it.
  5. Shut down all of the nodes and restart them, using mysqld_bootstrap to start only the first node, which should be the last one that was shutdown. If you have problems, check the grastate.dat file in the data directory to ensure the safe_to_bootstrap parameter is set to 1.

Note

If you struggled at any point in doing these exercises, especially in getting the Galera nodes started, you might want to do them again. Start with fresh installations of the servers, without MySQL or MariaDB or Galera Cluster. If you use the same servers, before doing the exercises again, uninstall the database software and Galera, and delete the data directory. Do the exercises multiple times until you’re able to install, configure, and start a Galera cluster without any problems.

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