Deploy a Galera Cluster Node with MariaDB Community Server 10.4 on Ubuntu 20.04 LTS
These instructions detail the deployment of MariaDB Community Server 10.4 on Ubuntu 20.04 LTS in a Galera Cluster Node configuration.
These instructions detail how to deploy a Galera Cluster node, which is suited for a transactional or OLTP workload that requires high availability (HA).
MariaDB Platform Components
These instructions detail the deployment of the following MariaDB Platform components:
Component
Description
MariaDB Community Server 10.4
It is a 100% Open Source modern SQL database.
MariaDB Galera Cluster
It combines MariaDB Community Server 10.4 and Galera Cluster.
MariaDB Community Server Components
These instructions detail the deployment of the following MariaDB Community Server components:
Component
Description
InnoDB
It is a general purpose storage engine.
It is ACID-compliant.
It is performant.
It is the transactional component of MariaDB's single stack Hybrid Transactional/Analytical Processing (HTAP) solution.
Galera Cluster
It provides virtually synchronous multi-primary replication for multiple MariaDB Community Servers.
It allows any node to handle reads and writes.
It replicates writes to every node in the cluster.
Term Definitions
Term
Definition
row database
A database where all columns of each row are stored together.
Best suited for transactional and OLTP workloads.
Also known as a "row-oriented database".
Installation
MariaDB Corporation provides a APT package repository for Ubuntu 20.04 LTS.
MariaDB Galera Cluster requires that you install an additional package for Galera Cluster to use the Server as a Cluster Node. Galera Cluster 4 is available for MariaDB Community Server 10.5 and 10.4. Galera Cluster 3 is available for MariaDB Community Server 10.3 and 10.2.
Install via APT (Debian/Ubuntu)
Configure the APT package repository.
To configure APT package repositories:
$ sudo apt install wget
$ wget https://downloads.mariadb.com/MariaDB/mariadb_repo_setup
$ echo "6528c910e9b5a6ecd3b54b50f419504ee382e4bdc87fa333a0b0fcd46ca77338 mariadb_repo_setup"
| sha256sum -c -
$ chmod +x mariadb_repo_setup
$ sudo ./mariadb_repo_setup
--mariadb-server-version="mariadb-10.4"
$ sudo apt update
Install MariaDB Community Server and package dependencies:
$ sudo apt install mariadb-server mariadb-backup
Install Galera.
To install MariaDB Galera Cluster for MariaDB Community Server 10.4, install Galera Cluster 4:
$ sudo apt install galera-4
Configure MariaDB.
Installation only loads MariaDB Community Server to the system. MariaDB Community Server requires configuration before the database server is ready for use.
Configuration
MariaDB Community Server can be configured in the following ways:
System variables and options can be set in a configuration file (such as /etc/my.cnf). MariaDB Community Server must be restarted to apply changes made to the configuration file.
System variables and options can be set on the command-line.
If a system variable supports dynamic changes, then it can be set on-the-fly using the SET statement.
Configuration Files
MariaDB's packages include several bundled configuration files. It is also possible to create custom configuration files.
On Debian and Ubuntu, MariaDB's packages bundle the following configuration files:
/etc/mysql/my.cnf
/etc/mysql/mariadb.cnf
/etc/mysql/mariadb.conf.d/50-client.cnf
/etc/mysql/mariadb.conf.d/50-mysql-clients.cnf
/etc/mysql/mariadb.conf.d/50-mysqld_safe.cnf
/etc/mysql/mariadb.conf.d/50-server.cnf
/etc/mysql/mariadb.conf.d/60-galera.cnf
And on Debian and Ubuntu, custom configuration files from the following directories are read by default:
/etc/mysql/conf.d/
/etc/mysql/mariadb.conf.d/
Configuring MariaDB
Determine which system variables and options you need to configure.
Mandatory system variables and options for MariaDB Galera Cluster include:
System Variable/Option
Description
wsrep_provider
Sets the path to the wsrep Provider. This is the path to the libgalera_smm.so file.
wsrep_cluster_address
Sets the Group Communications back-end (usually gcomm://), followed by a comma-separated list of IP addresses or domain names for each Cluster Node. It is best practice to include all Cluster Nodes in this list.
wsrep_cluster_name
Sets the logical name for the cluster. Must be the same on all Cluster Nodes.
binlog_format
Set to ROW, MariaDB Galera Cluster does not support other Binary Log formats.
innodb_autoinc_lock_mode
Set to 2, MariaDB Galera Cluster does not support other auto-increment lock modes.
wsrep_on
Set to ON to enable MariaDB Galera Cluster.
Useful system variables and options for MariaDB Community Server include:
System Variable/Option
Description
datadir
Sets the path to the data directory. MariaDB Community Server writes data files to this directory, including tablespaces, logs, and schemas. Change it to use a non-standard location or to start the Server on a different data directory for testing.
bind_address
Sets the local TCP/IP address on which MariaDB Community Server listens for incoming connections. Bind to 0.0.0.0 to make the Server accessible through any network interface.
port
Sets the port MariaDB Community Server listens on. Use this system variable to use a non-standard port or when running multiple Servers on the same host for testing.
max_connections
Sets the maximum number of simultaneous connections MariaDB Community Server allows.
thread_handling
Sets how MariaDB Community Server handles threads for client connections.
log_error
Sets the file name for the error log.
innodb_buffer_pool_size
Sets the amount of memory InnoDB reserves for the Buffer Pool.
innodb_log_file_size
Sets the size for each Redo Log file and innodb_log_files_in_group sets the number of Redo Log files used by InnoDB.
innodb_io_capacity
Sets the maximum number of I/O operations per second that InnoDB can use.
Useful system variables and options for MariaDB Galera Cluster include:
System Variable/Option
Description
wsrep_provider_options
Use to set wsrep Provider Options, which are passed to the Galera Replication plugin, allowing you to fine tune replication performance.
wsrep_slave_threads
Sets the number of threads the Cluster Node uses to apply replication events.
wsrep_sst_method
Sets the script the Cluster Node uses to perform State Snapshot Transfers (SST). Set to mariabackup to use MariaDB Backup.
wsrep_sst_auth
Sets the user name and password the Cluster Node uses to authenticate itself when connecting to a donor node for a State Snapshot Transfer (SST).
Choose a configuration file in which to configure your system variables and options.
It not recommended to make custom changes to one of the bundled configuration files. Instead, it is recommended to create a custom configuration file in one of the included directories. Configuration files in included directories are read in alphabetical order. If you want your custom configuration file to override the bundled configuration files, then it is a good idea to prefix the custom configuration file's name with a string that will be sorted last, such as z-.
On Debian and Ubuntu, a good custom configuration get more info file would be: /etc/mysql/mariadb.conf.d/z-custom-my.cnf
Set your system variables and options in the configuration file.
They need to be set in a group that will be read by mariadbd, such as [mariadb] or [server].
For example:
[mariadb]
# Server Configuration
log_error = mariadbd.err
innodb_buffer_pool_size = 1G
# Cluster Configuration
wsrep_provider = /usr/lib64/galera-4/libgalera_smm.so
wsrep_cluster_address = gcomm://192.0.2.1,192.0.2.2,192.0.2.3
wsrep_cluster_name = TestCluster
wsrep_on = ON
binlog_format = ROW
innodb_autoinc_lock_mode = 2
MariaDB Replication Configuration
MariaDB Replication can be used along with MariaDB Galera Cluster. For example, you may want to replicate between two MariaDB Galera Clusters in different data centers.
Options and system variables to consider when using MariaDB Replication with MariaDB Galera Cluster:
System Variable/Option
Description
log_bin
Set this option to enable the Binary Log, allowing the Cluster Node to operate as a Primary Server.
log_slave_updates
Sets a Cluster node to write all replicated transactions to the Binary Log, so that they can be replicated by any Replica Servers.
server_id
Sets a numeric identifier for the Server, must be unique across all Servers being used in MariaDB Replication.
wsrep_gtid_mode
Sets the Cluster Node to automatically update the joiner node's wsrep_gtid_domain_id value as the gtid_domain_id.
wsrep_gtid_domain_id
Sets the domain identifier to use in Galera transactions.
gtid_domain_id
Sets the domain identifier to use in non-Galera transactions.
gtid_strict_mode
Sets MariaDB Community Server to enforce global ordering for Global Transaction ID's.
Starting the Cluster
MariaDB Galera Cluster is composed of a series of MariaDB Community Servers configured to connect to one another and form a Primary Component.
If the cluster is not running, bootstrap the Primary Component on a single Cluster Node, then start the other MariaDB Community Servers normally. If the cluster is already running, start the Cluster Node as you would a normal MariaDB Community Server.
Bootstrapping the Primary Component
Cluster Nodes start as non-operational components. When they start, they attempt to connect to other MariaDB Community Servers listed in the wsrep_cluster_address system variable. When the Node finds the Primary Component, it requests a state transfer to update its local database and then becomes operational.
If the Cluster Node never finds the Primary Component, it remains non-operational and fails.
If the cluster is not running, you need to bootstrap the Primary Component on the first node you start.
Note, this is only done on the first node you start. Use the normal process management system to start all other nodes in the cluster.
When using systemd (most supported OSes), bootstrap the Primary Component using the sudo galera_new_cluster script:
$ sudo galera_new_cluster
Starting the Server
MariaDB Community Server includes configuration to start, stop, restart, enable/disable on boot, and check the status of the Server using the operating system default process management system.
Note that when the cluster is not running, you need to bootstrap the first Server.
Ubuntu 20.04 LTS uses systemd. You can manage the Server process using the systemctl command:
Operation
Command
Start
sudo systemctl start mariadb
Stop
sudo systemctl stop mariadb
Restart
sudo systemctl restart mariadb
Enable during startup
sudo systemctl enable mariadb
Disable during startup
sudo systemctl disable mariadb
Status
sudo systemctl status mariadb
Bootstrap a cluster node
sudo galera_new_cluster
Recover a cluster node's position
sudo galera_recovery
Testing
When you have the Primary Component bootstrapped on the first Cluster and all the other Cluster Nodes started, you should test to ensure that they are working correctly and that there aren't any issues with the cluster.
Checking Cluster
Connect to any Cluster Node using MariaDB Client:
$ sudo mariadb
Welcome to the MariaDB monitor. Commands end with ; or g.
Your MariaDB connection id is 38
Server version: 10.4.17-MariaDB MariaDB Server
Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.
Type 'help;' or 'h' for help. Type 'c' to clear the current input statement.
MariaDB [(none)]>
Check the wsrep_cluster_size status variable using the SHOW GLOBAL STATUS statement:
SHOW GLOBAL STATUS LIKE 'wsrep_cluster_size';
+--------------------+-------+
| Variable_name | Value |
+--------------------+-------+
| wsrep_cluster_size | 3 |
+--------------------+-------+
The size of the cluster should equal the current number of Cluster Nodes. If it is lower than expected, one or more of the Cluster Nodes either did not start correctly or are unable to connect to the Primary Component.
Testing Replication
Connect to a Cluster Node and start MariaDB Client:
user@cluster-node1$ sudo mariadb
Create a database with the CREATE DATABASE statement:
CREATE DATABASE IF NOT EXISTS test;
Create a table with the CREATE TABLE statement:
CREATE TABLE test.names (
id INT PRIMARY KEY AUTO_INCREMENT,
name VARCHAR(255));
Insert some data with the INSERT statement:
INSERT INTO test.names(name) VALUES
("Walker Percy"), ("Kate Chopin"), ("William Faulkner"), ("Jane Austen");
Confirm that the data was inserted properly with the SELECT statement:
SELECT * FROM test.names;
+----+------------------+
| id | name |
+----+------------------+
| 1 | Walker Percy |
| 2 | Kate Chopin |
| 3 | William Faulkner |
| 4 | Jane Austen |
+----+------------------+
Connect to different Cluster Node and start MariaDB Client:
user@cluster-node2$ sudo mariadb
Confirm that the data was replicated properly with the SELECT statement:
SELECT * FROM test.names;
+----+------------------+
| id | name |
+----+------------------+
| 1 | Walker Percy |
| 2 | Kate Chopin |
| 3 | William Faulkner |
| 4 | Jane Austen |
+----+------------------+
We can confirm that the DDL and DML were replicated from the other Cluster Node, allowing all Servers in the cluster to return the same data.
Next steps:
Deploy MaxScale with Galera Monitor and Read/Write Split Router
Deploy MaxScale with Galera Monitor and Read Connection Router