mysqld_multi

mysqld_multi is designed to manage several mysqld processes that listen for connections on different Unix socket files and TCP/IP ports. It can start or stop servers, or report their current status.

mysqld_multi searches for groups named [mysqldN] in my.cnf (or in the file named by the --config-file option). N can be any positive integer. This number is referred to in the following discussion as the option group number, or GNR. Group numbers distinguish option groups from one another and are used as arguments to mysqld_multi to specify which servers you want to start, stop, or obtain a status report for. Options listed in these groups are the same that you would use in the [mysqld] group used for starting mysqld. However, when using multiple servers, it is necessary that each one use its own value for options such as the Unix socket file and TCP/IP port number.

To invoke mysqld_multi, use the following syntax:

mysqld_multi [options] {start|stop|report} [GNR[,GNR] ...]

start, stop, and report indicate which operation to perform. You can perform the designated operation for a single server or multiple servers, depending on the GNR list that follows the option name. If there is no list, mysqld_multi performs the operation for all servers in the option file.

Each GNR value represents an option group number or range of group numbers. The value should be the number at the end of the group name in the option file. For example, the GNR for a group named [mysqld17] is 17. To specify a range of numbers, separate the first and last numbers by a dash. The GNR value 10-13 represents groups [mysqld10] through [mysqld13]. Multiple groups or group ranges can be specified on the command line, separated by commas. There must be no whitespace characters (spaces or tabs) in the GNR list; anything after a whitespace character is ignored.

This command starts a single server using option group [mysqld17]:

mysqld_multi start 17

This command stops several servers, using option groups [mysqld8] and [mysqld10] through [mysqld13]:

mysqld_multi stop 8,10-13

For an example of how you might set up an option file, use this command:

mysqld_multi --example

mysqld_multi searches for option files as follows:

• With --no-defaults, no option files are read.
• With --defaults-file=file_name, only the named file is read.
• Otherwise, option files in the standard list of locations are read, including any file named by the --defaults-extra-file=file_nameoption, if one is given. (If the option is given multiple times, the last value is used.)

Option files read are searched for [mysqld_multi] and [mysqldN] option groups. The [mysqld_multi] group can be used for options to mysqld_multi itself. [mysqldN] groups can be used for options passed to specific mysqld instances.

The [mysqld] or [mysqld_safe] groups can be used for common options read by all instances of mysqld or mysqld_safe. You can specify a --defaults-file=file_name option to use a different configuration file for that instance, in which case the [mysqld] or [mysqld_safe] groups from that file will be used for that instance.

mysqld_multi Options

mysqld_multi supports the following options:

Make sure that the MariaDB account used for stopping the mysqld servers (with the mysqladmin program) has the same user name and password for each server. Also, make sure that the account has the SHUTDOWN privilege. If the servers that you want to manage have different user names or passwords for the administrative accounts, you might want to create an account on each server that has the same user name and password. For example, you might set up a common multi_admin account by executing the following commands for each server:

shell> mysql -u root -S /tmp/mysql.sock -p
Enter password:
mysql> GRANT SHUTDOWN ON *.*
 -> TO ´multi_admin´@´localhost´ IDENTIFIED BY ´multipass´;

Change the connection parameters appropriately when connecting to each one. Note that the host name part of the account name must allow you to connect as multi_admin from the host where you want to run mysqld_multi.

The Unix socket file and the TCP/IP port number must be different for every mysqld. (Alternatively, if the host has multiple network addresses, you can use --bind-address to cause different servers to listen to different interfaces.)

The --pid-file option is very important if you are using mysqld_safe to start mysqld (for example, --mysqld=mysqld_safe) Every mysqld should have its own process ID file. The advantage of using mysqld_safe instead of mysqld is that mysqld_safe monitors its mysqld process and restarts it if the process terminates due to a signal sent using kill -9 or for other reasons, such as a segmentation fault. Please note that the mysqld_safe script might require that you start it from a certain place. This means that you might have to change location to a certain directory before running mysqld_multi. If you have problems starting, please see the mysqld_safe script. Check especially the lines:

               ----------------------------------------------------------------
               MY_PWD=`pwd`
               # Check if we are starting this relative (for the binary release)
               if test -d $MY_PWD/data/mysql -a \
                  -f ./share/mysql/english/errmsg.sys -a \
                  -x ./bin/mysqld
               ----------------------------------------------------------------

The test performed by these lines should be successful, or you might encounter problems. See mysqld_safe.

You might want to use the --user option for mysqld, but to do this you need to run the mysqld_multi script as the Unix root user. Having the option in the option file doesn´t matter; you just get a warning if you are not the superuser and the mysqld processes are started under your own Unix account.

The following example shows how you might set up an option file for use with mysqld_multi. The order in which the mysqld programs are started or stopped depends on the order in which they appear in the option file. Group numbers need not form an unbroken sequence. The first and fifth [mysqldN] groups were intentionally omitted from the example to illustrate that you can have “gaps” in the option file. This gives you more flexibility.

           # This file should probably be in your home dir (~/.my.cnf)
           # or /etc/my.cnf
           # Version 2.1 by Jani Tolonen
           [mysqld_multi]
           mysqld     = /usr/local/bin/mysqld_safe
           mysqladmin = /usr/local/bin/mysqladmin
           user       = multi_admin
           password   = multipass
           [mysqld2]
           socket     = /tmp/mysql.sock2
           port       = 3307
           pid-file   = /usr/local/mysql/var2/hostname.pid2
           datadir    = /usr/local/mysql/var2
           language   = /usr/local/share/mysql/english
           user       = john
           [mysqld3]
           socket     = /tmp/mysql.sock3
           port       = 3308
           pid-file   = /usr/local/mysql/var3/hostname.pid3
           datadir    = /usr/local/mysql/var3
           language   = /usr/local/share/mysql/swedish
           user       = monty
           [mysqld4]
           socket     = /tmp/mysql.sock4
           port       = 3309
           pid-file   = /usr/local/mysql/var4/hostname.pid4
           datadir    = /usr/local/mysql/var4
           language   = /usr/local/share/mysql/estonia
           user       = tonu
           [mysqld6]
           socket     = /tmp/mysql.sock6
           port       = 3311
           pid-file   = /usr/local/mysql/var6/hostname.pid6
           datadir    = /usr/local/mysql/var6
           language   = /usr/local/share/mysql/japanese
           user       = jani