#11: Use conf.d directory instead of changing my.cnf (fixes #9)

Remove default values from template, use default values
maintained by distribution instead. Include only values we want to override in the charm
provided config file.

hooks/config-changed

@@ -214,149 +214,18 @@ template="""
 #
 #
 ######################################
-#
-# The MySQL database server configuration file.
-#
-# You can copy this to one of:
-# - "/etc/mysql/my.cnf" to set global options,
-# - "~/.my.cnf" to set user-specific options.
-#
-# One can use all long options that the program supports.
-# Run program with --help to get a list of available options and with
-# --print-defaults to see which it would actually understand and use.
-#
-# For explanations see
-# http://dev.mysql.com/doc/mysql/en/server-system-variables.html
-
-# This will be passed to all mysql clients
-# It has been reported that passwords should be enclosed with ticks/quotes
-# escpecially if they contain "#" chars...
-# Remember to edit /etc/mysql/debian.cnf when changing the socket location.
-[client]
-port		= 3306
-socket		= /var/run/mysqld/mysqld.sock
-
-# Here is entries for some specific programs
-# The following values assume you have at least 32M ram
-
-# This was formally known as [safe_mysqld]. Both versions are currently parsed.
-[mysqld_safe]
-socket		= /var/run/mysqld/mysqld.sock
-nice		= 0
-
 [mysqld]
-#
-# * Basic Settings
-#
-
-#
-# * IMPORTANT
-#   If you make changes to these settings and your system uses apparmor, you may
-#   also need to also adjust /etc/apparmor.d/usr.sbin.mysqld.
-#
-
-user		= mysql
-socket		= /var/run/mysqld/mysqld.sock
-port		= 3306
-basedir		= /usr
-datadir		= /var/lib/mysql
-tmpdir		= /tmp
-skip-external-locking
-#
-# Instead of skip-networking the default is now to listen only on
-# localhost which is more compatible and is not less secure.
 bind-address		= %(bind-address)s
-#
-# * Fine Tuning
-#
 key_buffer_size		= %(key-buffer)s
-max_allowed_packet	= 16M
-# This replaces the startup script and checks MyISAM tables if needed
-# the first time they are touched
-myisam-recover         = BACKUP
 %(max-connections)s
 %(wait-timeout)s
-#table_cache            = 64
-#thread_concurrency     = 10
-#
-# * Query Cache Configuration
-#
-query_cache_limit = 1M
 query_cache_size = %(query-cache-size)s
 query_cache_type = %(query-cache-type)s
-#
-# * Logging and Replication
-#
-# Both location gets rotated by the cronjob.
-# Be aware that this log type is a performance killer.
-# As of 5.1 you can enable the log at runtime!
-#general_log_file        = /var/log/mysql/mysql.log
-#general_log             = 1
-
-log_error                = /var/log/mysql/error.log
-
-# Here you can see queries with especially long duration
-#log_slow_queries	= /var/log/mysql/mysql-slow.log
-#long_query_time = 2
-#log-queries-not-using-indexes
-#
-# The following can be used as easy to replay backup logs or for replication.
-# note: if you are setting up a replication slave, see README.Debian about
-#       other settings you may need to change.
-#server-id		= 1
-#log_bin			= /var/log/mysql/mysql-bin.log
-expire_logs_days	= 10
-max_binlog_size         = 100M
-#binlog_do_db		= include_database_name
-#binlog_ignore_db	= include_database_name
-#
-# * InnoDB
-#
-# InnoDB is enabled by default with a 10MB datafile in /var/lib/mysql/.
-# We also set innodb_file_per_table to avoid having ibdata1 fill the disk.
-# Read the manual for more InnoDB related options. There are many!
-#
-innodb_file_per_table
+
 innodb_buffer_pool_size = %(innodb-buffer-pool-size)s
 innodb_flush_log_at_trx_commit = %(innodb-flush-log-at-trx-commit)s
 sync_binlog = %(sync-binlog)s
 default_storage_engine = %(default-storage-engine)s
-skip-name-resolve
-# * Security Features
-#
-# Read the manual, too, if you want chroot!
-# chroot = /var/lib/mysql/
-#
-# For generating SSL certificates I recommend the OpenSSL GUI "tinyca".
-#
-# ssl-ca=/etc/mysql/cacert.pem
-# ssl-cert=/etc/mysql/server-cert.pem
-# ssl-key=/etc/mysql/server-key.pem
-
-#
-# * Encoding
-#
-# Set all the tables to utf8 by default.
-collation-server = utf8_general_ci
-init-connect='SET NAMES utf8'
-character-set-server = utf8
-
-[mysqldump]
-quick
-quote-names
-max_allowed_packet	= 16M
-
-[mysql]
-#no-auto-rehash	# faster start of mysql but no tab completition
-
-[isamchk]
-key_buffer_size		= 16M
-
-#
-# * IMPORTANT: Additional settings that can override those from this file!
-#   The files must end with '.cnf', otherwise they'll be ignored.
-#
-!includedir /etc/mysql/conf.d/
 """
 
 i_am_a_slave = os.path.isfile('/var/lib/juju/i.am.a.slave')
@@ -378,8 +247,17 @@ binlog_format = %s
 
 mycnf=template % configs
 
-targets = {'/etc/mysql/conf.d/binlog.cnf': binlog_cnf,
-           '/etc/mysql/my.cnf': mycnf,
+target_prefix='/etc/mysql/conf.d'
+if os.path.exists('/etc/mysql/mysql.conf.d'):
+    # configuration files in this directory have precedence
+    target_prefix='/etc/mysql/mysql.conf.d'
+
+# Naming of config files is crucial. The values read from the last file loaded
+# will take precedence. On Xenial and newer there is a complete MySQL
+# configuration file in /etc/mysql/mysql.conf.d/mysqld.cnf. Naming our file
+# 'mysqld_settings_charm.cnf' will make it load after that.
+targets = {os.path.join(target_prefix, 'binlog.cnf'): binlog_cnf,
+           os.path.join(target_prefix, 'mysqld_settings_charm.cnf'): mycnf,
            }
 
 need_restart = False
@@ -404,6 +282,7 @@ for target,content in targets.iteritems():
                     need_restart = True
         else:
             need_restart = True
+        os.chmod(t.name, 0o644)
         os.rename(t.name, target)
 
 if need_restart: