New parser: my_print_defaults

Both MariaDB and MySQL provide my_print_defaults for displaying MariaDB / MySQL configuration.

They are not exactly the same, for example the MySQL version has a -s option and the MariaDB version doesn’t, but I don’t think the differences would matter for a jc parser.

Usage examples:

my_print_defaults -c /home/example/.my.cnf client
--user=example
--password=XXX
--socket=/run/mysqld/mysqld.sock

my_print_defaults -c /etc/mysql/mariadb.conf.d/50-server.cnf mysqld
--user=mysql
--pid-file=/var/run/mysqld/mysqld.pid
--socket=/var/run/mysqld/mysqld.sock
--port=3306
--basedir=/usr
--datadir=/var/lib/mysql
--tmpdir=/tmp
--lc-messages-dir=/usr/share/mysql
--skip-external-locking
--bind-address=127.0.0.1
--key_buffer_size=16M
--max_allowed_packet=64M
--thread_stack=192K
--thread_cache_size=8
--myisam_recover_options=BACKUP
--max_connections=80
--max_user_connections=0
--table_cache=64
--thread_concurrency=10
--open_files_limit=122880
--table_open_cache=6000
--tmp_table_size=32M
--join_buffer_size=8M
--max_heap_table_size=32M
--query_cache_type=0
--query_cache_limit=0
--query_cache_size=0
--log_error=/var/log/mysql/error.log
--expire_logs_days=10
--max_binlog_size=100M
--innodb_buffer_pool_size=1G
--innodb_log_file_size=256M
--character-set-server=utf8mb4
--collation-server=utf8mb4_general_ci

I think that producing JSON would be a matter of, for each line of results, removing the -- at the start, then splitting the string at the = sign.

Note that the use of - or _ in configuration options is interchangable, perhaps it would make sense to change all dashes in variable names into underscores for consistency?

[kellyjonbrazil]

Yeah I can fix that. I already do it for double quotes but didn’t think to do it for single quotes. You can use the -r or raw option to get the quotes back, if needed.

[chriscroome]

The mysqltuner Perl script has a --json output option available after libjson-perl has been installed and this together with my_print_defaults and the jc --kv parser results in so much JSON data that I think this issue can be closed! Thanks for considering it @kellyjonbrazil

Note however that some of the variables names have spaces in them so you might need to use something else to filter the results before they can easily be accessed by something like Ansible, for example:

mysqltuner --json | jq '."Adjust variables"'
[
  "query_cache_size (=0)",
  "query_cache_type (=0)",
  "tmp_table_size (> 16M)",
  "max_heap_table_size (> 16M)",
  "performance_schema = ON enable PFS",
  "innodb_buffer_pool_size (>= 960.2M) if possible.",
  "innodb_log_file_size should be (=64M) if possible, so InnoDB total log files size equals to 25% of buffer pool size."
]