MariaDB 10.1 SQL Database Server Docker image

This container image includes MariaDB 10.1 SQL database server for OpenShift and general usage. Users can choose between RHEL and CentOS based images. The RHEL image is available in the Red Hat Container Catalog as registry.access.redhat.com/rhscl/mariadb-101-rhel7. The CentOS image is then available on Docker Hub as centos/mariadb-101-centos7.

Description

This container image provides a containerized packaging of the MariaDB mysqld daemon and client application. The mysqld server daemon accepts connections from clients and provides access to content from MySQL databases on behalf of the clients. You can find more information on the MariaDB project from the project Web site (https://mariadb.org/).

Usage

For this, we will assume that you are using the MariaDB 10.1 container image from the Red Hat Container Catalog called rhscl/mariadb-101-rhel7. If you want to set only the mandatory environment variables and not store the database in a host directory, execute the following command:

$ docker run -d --name mariadb_database -e MYSQL_USER=user -e MYSQL_PASSWORD=pass -e MYSQL_DATABASE=db -p 3306:3306 rhscl/mariadb-101-rhel7

This will create a container named mariadb_database running MySQL with database db and user with credentials user:pass. Port 3306 will be exposed and mapped to the host. If you want your database to be persistent across container executions, also add a -v /host/db/path:/var/lib/mysql/data argument. This will be the MySQL data directory.

If the database directory is not initialized, the entrypoint script will first run mysql_install_db and setup necessary database users and passwords. After the database is initialized, or if it was already present, mysqld is executed and will run as PID 1. You can stop the detached container by running docker stop mariadb_database.

Environment variables and volumes

The image recognizes the following environment variables that you can set during initialization by passing -e VAR=VALUE to the Docker run command.

MYSQL_USER
User name for MySQL account to be created

MYSQL_PASSWORD
Password for the user account

MYSQL_DATABASE
Database name

MYSQL_ROOT_PASSWORD
Password for the root user (optional)

The following environment variables influence the MySQL configuration file. They are all optional.

MYSQL_LOWER_CASE_TABLE_NAMES (default: 0)
Sets how the table names are stored and compared

MYSQL_MAX_CONNECTIONS (default: 151)
The maximum permitted number of simultaneous client connections

MYSQL_MAX_ALLOWED_PACKET (default: 200M)
The maximum size of one packet or any generated/intermediate string

MYSQL_FT_MIN_WORD_LEN (default: 4)
The minimum length of the word to be included in a FULLTEXT index

MYSQL_FT_MAX_WORD_LEN (default: 20)
The maximum length of the word to be included in a FULLTEXT index

MYSQL_AIO (default: 1)
Controls the innodb_use_native_aio setting value in case the native AIO is broken. See http://help.directadmin.com/item.php?id=529

MYSQL_TABLE_OPEN_CACHE (default: 400)
The number of open tables for all threads

MYSQL_KEY_BUFFER_SIZE (default: 32M or 10% of available memory)
The size of the buffer used for index blocks

MYSQL_SORT_BUFFER_SIZE (default: 256K)
The size of the buffer used for sorting

MYSQL_READ_BUFFER_SIZE (default: 8M or 5% of available memory)
The size of the buffer used for a sequential scan

MYSQL_INNODB_BUFFER_POOL_SIZE (default: 32M or 50% of available memory)
The size of the buffer pool where InnoDB caches table and index data

MYSQL_INNODB_LOG_FILE_SIZE (default: 8M or 15% of available available)
The size of each log file in a log group

MYSQL_INNODB_LOG_BUFFER_SIZE (default: 8M or 15% of available memory)
The size of the buffer that InnoDB uses to write to the log files on disk

MYSQL_DEFAULTS_FILE (default: /etc/my.cnf)
Point to an alternative configuration file

MYSQL_BINLOG_FORMAT (default: statement)
Set sets the binlog format, supported values are row and statement

MYSQL_LOG_QUERIES_ENABLED (default: 0)
To enable query logging set this to 1

You can also set the following mount points by passing the -v /host:/container flag to Docker.

/var/lib/mysql/data
MySQL data directory

Notice: When mouting a directory from the host into the container, ensure that the mounted directory has the appropriate permissions and that the owner and group of the directory matches the user UID or name which is running inside the container.

MariaDB auto-tuning

When the MySQL image is run with the --memory parameter set and you didn't specify value for some parameters, their values will be automatically calculated based on the available memory.

MYSQL_KEY_BUFFER_SIZE (default: 10%)
key_buffer_size

MYSQL_READ_BUFFER_SIZE (default: 5%)
read_buffer_size

MYSQL_INNODB_BUFFER_POOL_SIZE (default: 50%)
innodb_buffer_pool_size

MYSQL_INNODB_LOG_FILE_SIZE (default: 15%)
innodb_log_file_size

MYSQL_INNODB_LOG_BUFFER_SIZE (default: 15%)
innodb_log_buffer_size

MySQL root user

The root user has no password set by default, only allowing local connections. You can set it by setting the MYSQL_ROOT_PASSWORD environment variable. This will allow you to login to the root account remotely. Local connections will still not require a password.

To disable remote root access, simply unset MYSQL_ROOT_PASSWORD and restart the container.

Changing passwords

Since passwords are part of the image configuration, the only supported method to change passwords for the database user (MYSQL_USER) and root user is by changing the environment variables MYSQL_PASSWORD and MYSQL_ROOT_PASSWORD, respectively.

Changing database passwords through SQL statements or any way other than through the environment variables aforementioned will cause a mismatch between the values stored in the variables and the actual passwords. Whenever a database container starts it will reset the passwords to the values stored in the environment variables.

Default my.cnf file

With environment variables we are able to customize a lot of different parameters or configurations for the mysql bootstrap configurations. If you'd prefer to use your own configuration file, you can override the MYSQL_DEFAULTS_FILE env variable with the full path of the file you wish to use. For example, the default location is /etc/my.cnf but you can change it to /etc/mysql/my.cnf by setting MYSQL_DEFAULTS_FILE=/etc/mysql/my.cnf

Extending image

This image can be extended using source-to-image.

For example, to build a customized MariaDB database image my-mariadb-rhel7 with a configuration in ~/image-configuration/ run:

$ s2i build ~/image-configuration/ rhscl/mariadb-101-rhel7 my-mariadb-rhel7

The directory passed to s2i build can contain these directories:

mysql-cfg/ When starting the container, files from this directory will be used as a configuration for the mysqld daemon. envsubst command is run on this file to still allow customization of the image using environmental variables

mysql-pre-init/ Shell scripts (*.sh) available in this directory are sourced before mysqld daemon is started.

mysql-init/ Shell scripts (*.sh) available in this directory are sourced when mysqld daemon is started locally. In this phase, use ${mysql_flags} to connect to the locally running daemon, for example mysql $mysql_flags < dump.sql

Variables that can be used in the scripts provided to s2i:

$mysql_flags arguments for the mysql tool that will connect to the locally running mysqld during initialization

$MYSQL_RUNNING_AS_MASTER variable defined when the container is run with run-mysqld-master command

$MYSQL_RUNNING_AS_SLAVE variable defined when the container is run with run-mysqld-slave command

$MYSQL_DATADIR_FIRST_INIT variable defined when the container was initialized from the empty data dir

During s2i build all provided files are copied into /opt/app-root/src directory into the resulting image. If some configuration files are present in the destination directory, files with the same name are overwritten. Also only one file with the same name can be used for customization and user provided files are preferred over default files in /usr/share/container-scripts/mysql/- so it is possible to overwrite them.

Same configuration directory structure can be used to customize the image every time the image is started using docker run. The directory has to be mounted into /opt/app-root/src/ in the image (-v ./image-configuration/:/opt/app-root/src/). This overwrites customization built into the image.

Securing the connection with SSL

In order to secure the connection with SSL, use the extending feature described above. In particular, put the SSL certificates into a separate directory:

sslapp/mysql-certs/server-cert-selfsigned.pem
sslapp/mysql-certs/server-key.pem

And then put a separate configuration file into mysql-cfg:

$> cat sslapp/mysql-cfg/ssl.cnf
[mysqld]
ssl-key=${APP_DATA}/mysql-certs/server-key.pem
ssl-cert=${APP_DATA}/mysql-certs/server-cert-selfsigned.pem

Such a directory sslapp can then be mounted into the container with -v, or a new container image can be built using s2i.

Upgrading and data directory version checking

MySQL and MariaDB use versions that consist of three numbers X.Y.Z (e.g. 5.6.23). For version changes in Z part, the server's binary data format stays compatible and thus no special upgrade procedure is needed. For upgrades from X.Y to X.Y+1, consider doing manual steps as described at https://mariadb.com/kb/en/library/upgrading-from-mariadb-100-to-mariadb-101/

Skipping versions like from X.Y to X.Y+2 or downgrading to lower version is not supported; the only exception is ugrading from MariaDB 5.5 to MariaDB 10.0.

Important: Upgrading to a new version is always risky and users are expected to make a full back-up of all data before.

A safer solution to upgrade is to dump all data using mysqldump or mysqldbexport and then load the data using mysql or mysqldbimport into an empty (freshly initialized) database.

Another way of proceeding with the upgrade is starting the new version of the mysqld daemon and run mysql_upgrade right after the start. This so called in-place upgrade is generally faster for large data directory, but only possible if upgrading from the very previous version, so skipping versions is not supported.

This container detects whether the data needs to be upgraded using mysql_upgrade and we can control it by setting MYSQL_DATADIR_ACTION variable, which can have one or more of the following values:

• upgrade-warn -- If the data version can be determined and the data come from a different version of the daemon, a warning is printed but the container starts. This is the default value. Since historically the version file mysql_upgrade_info was not created, when using this option, the version file is created if not exist, but no mysql_upgrade will be called. However, this automatic creation will be removed after few months, since the version should be created on most deployments at that point.
• upgrade-auto -- mysql_upgrade is run at the beginning of the container start, when the local daemon is running, but only if the data version can be determined and the data come with the very previous version. A warning is printed if the data come from even older or newer version. This value effectively enables automatic upgrades, but it is always risky and users should still back-up all the data before starting the newer container. Set this option only if you have very good back-ups at any moment and you are fine to fail-over from the back-up.
• upgrade-force -- mysql_upgrade --force is run at the beginning of the container start, when the local daemon is running, no matter what version of the daemon the data come from. This is also the way to create the missing version file mysql_upgrade_info if not present in the root of the data directory; this file holds information about the version of the data.

There are also some other actions that you may want to run at the beginning of the container start, when the local daemon is running, no matter what version of the data is detected:

• optimize -- runs mysqlcheck --optimize. It optimizes all the tables.
• analyze -- runs mysqlcheck --analyze. It analyzes all the tables.
• disable -- nothing is done regarding data directory version.

Multiple values are separated by comma and run in-order, e.g. MYSQL_DATADIR_ACTION="optimize,analyze".

Changing the replication binlog_format

Some applications may wish to use row binlog_formats (for example, those built with change-data-capture in mind). The default replication/binlog format is statement but to change it you can set the MYSQL_BINLOG_FORMAT environment variable. For example MYSQL_BINLOG_FORMAT=row. Now when you run the database with master replication turned on (ie, set the Docker/container cmd to be run-mysqld-master) the binlog will emit the actual data for the rows that change as opposed to the statements (ie, DML like insert...) that caused the change.

Troubleshooting

The mysqld deamon in the container logs to the standard output, so the log is available in the container log. The log can be examined by running:

docker logs <container>

See also

Dockerfile and other sources for this container image are available on https://github.com/sclorg/mariadb-container. In that repository, Dockerfile for CentOS is called Dockerfile, Dockerfile for RHEL is called Dockerfile.rhel7.