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Short Description
MariaDB 10.1 SQL database server
Full Description

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.

Variable name Description
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.

Variable name Description Default
MYSQL_LOWER_CASE_TABLE_NAMES Sets how the table names are stored and compared 0
MYSQL_MAX_CONNECTIONS The maximum permitted number of simultaneous client connections 151
MYSQL_MAX_ALLOWED_PACKET The maximum size of one packet or any generated/intermediate string 200M
MYSQL_FT_MIN_WORD_LEN The minimum length of the word to be included in a FULLTEXT index 4
MYSQL_FT_MAX_WORD_LEN The maximum length of the word to be included in a FULLTEXT index 20
MYSQL_AIO Controls the innodb_use_native_aio setting value in case the native AIO is broken. See http://help.directadmin.com/item.php?id=529 1
MYSQL_TABLE_OPEN_CACHE The number of open tables for all threads 400
MYSQL_KEY_BUFFER_SIZE The size of the buffer used for index blocks 32M (or 10% of available memory)
MYSQL_SORT_BUFFER_SIZE The size of the buffer used for sorting 256K
MYSQL_READ_BUFFER_SIZE The size of the buffer used for a sequential scan 8M (or 5% of available memory)
MYSQL_INNODB_BUFFER_POOL_SIZE The size of the buffer pool where InnoDB caches table and index data 32M (or 50% of available memory)
MYSQL_INNODB_LOG_FILE_SIZE The size of each log file in a log group 8M (or 15% of available available)
MYSQL_INNODB_LOG_BUFFER_SIZE The size of the buffer that InnoDB uses to write to the log files on disk 8M (or 15% of available memory)
MYSQL_DEFAULTS_FILE Point to an alternative configuration file /etc/my.cnf
MYSQL_BINLOG_FORMAT Set sets the binlog format, supported values are row and statement statement

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

Volume mount point Description
/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.

Variable name Configuration parameter Relative value
MYSQL_KEY_BUFFER_SIZE key_buffer_size 10%
MYSQL_READ_BUFFER_SIZE read_buffer_size 5%
MYSQL_INNODB_BUFFER_POOL_SIZE innodb_buffer_pool_size 50%
MYSQL_INNODB_LOG_FILE_SIZE innodb_log_file_size 15%
MYSQL_INNODB_LOG_BUFFER_SIZE innodb_log_buffer_size 15%

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.

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.

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