Add encoding hints for mysql, mariadb, and percona

[yosifkit]

Needs docker-library/mysql#147, docker-library/percona#15, MariaDB/mariadb-docker#45 for end user clarity when using --help.

$ # new:
$ docker run -it --rm maridb --help
mysqld  Ver 10.1.11-MariaDB-1~jessie for debian-linux-gnu on x86_64 (mariadb.org binary distribution)
Copyright (c) 2000, 2015, Oracle, MariaDB Corporation Ab and others.

Starts the MariaDB database server.

Usage: mysqld [OPTIONS]

For more help options (several pages), use mysqld --verbose --help.
$ # old, one of the password options is required to get anywhere
$ docker run -it --rm -e MYSQL_ALLOW_EMPTY_PASSWORD=1 mariadb --help
...# tons of output creating the initial database

Database initialized
MySQL init process in progress...
mysqld  Ver 10.1.11-MariaDB-1~jessie for debian-linux-gnu on x86_64 (mariadb.org binary distribution)
Copyright (c) 2000, 2015, Oracle, MariaDB Corporation Ab and others.

Starts the MariaDB database server.

Usage: mysqld [OPTIONS]

For more help options (several pages), use mysqld --verbose --help.
MySQL init process in progress...
MySQL init process in progress...
MySQL init process in progress...
MySQL init process in progress...
MySQL init process in progress...
MySQL init process in progress...
MySQL init process in progress...
MySQL init process in progress...
MySQL init process in progress...
MySQL init process in progress...
MySQL init process in progress...
MySQL init process in progress...
MySQL init process in progress...
MySQL init process in progress...
MySQL init process in progress...
MySQL init process in progress...
MySQL init process in progress...
MySQL init process in progress...
MySQL init process in progress...
MySQL init process in progress...
MySQL init process in progress...
MySQL init process in progress...
MySQL init process in progress...
MySQL init process in progress...
MySQL init process in progress...
MySQL init process in progress...
MySQL init process in progress...
MySQL init process in progress...
MySQL init process in progress...
MySQL init process in progress...
MySQL init process failed.

Fixes docker-library/mysql#14
(replaces) Fixes #237

[yosifkit]

Example setting character set and collation for the server:

$ docker run -d --name mysql -e MYSQL_ALLOW_EMPTY_PASSWORD=1 -e MYSQL_DATABASE=testing mysql --character-set-server=utf8 --collation-server=utf8_unicode_ci
$ docker run -it --link mysql:mysql --rm mysql mysql -hmysql -uroot
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 5
Server version: 5.7.11 MySQL Community Server (GPL)

Copyright (c) 2000, 2016, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> SELECT schema_name, DEFAULT_CHARACTER_SET_NAME, DEFAULT_COLLATION_NAME FROM INFORMATION_SCHEMA.SCHEMATA;
+--------------------+----------------------------+------------------------+
| schema_name        | DEFAULT_CHARACTER_SET_NAME | DEFAULT_COLLATION_NAME |
+--------------------+----------------------------+------------------------+
| information_schema | utf8                       | utf8_general_ci        |
| mysql              | utf8                       | utf8_unicode_ci        |
| performance_schema | utf8                       | utf8_general_ci        |
| sys                | utf8                       | utf8_general_ci        |
| testing            | utf8                       | utf8_unicode_ci        |
+--------------------+----------------------------+------------------------+
5 rows in set (0.00 sec)

mysql> ^DBye

[tianon]

IMO we should change "utf8" to "UTF-8 (utf8mb4)" and update the example below so that we're recommending "real" UTF-8, not the broken 3-byte version 😄

[tianon]

LGTM otherwise, pending those --help PRs

[yosifkit]

Updated!

[tianon]

Now waiting on docker-library/official-images#1533 -- once that merges, we're good to go here.

[yosifkit]

docker-library/official-images#1533 merged; will merge once they are built and pushed to the hub.