Added documentation.

@cindex tools, mysqld_multi

@cindex scripts

@cindex multi mysqld

@cindex @code{mysqld_multi}

@node  mysqld_multi, mysql, safe_mysqld, Tools

@section mysqld_multi, program for managing multiple @code{MySQL} servers

@example

shell> mysql -u root -S /tmp/mysql.sock -proot_password -e

"GRANT SHUTDOWN ON *.* TO multi_admin@@localhost IDENTIFIED BY 'multipass'"

@xref{Privileges}.

@end example

You will have to do the above for each @code{mysqld} running in each

data directory, that you have (just change the socket, -S=...)

release) if test -d /data/mysql -a -f ./share/mysql/english/errmsg.sys

-a -x ./bin/mysqld

--------------------------------------------------------------------------

@xref{safe_mysqld}.

@end example

The above test should be successful, or you may encounter problems.

@item

performance in a threaded system!

@end itemize

@xref{Multiple servers}.

This is an example of the config file on behalf of @code{mysqld_multi}. 

@example

user       = jani

@end example

@xref{Option files}.

@cindex command line tool

@cindex tools, command line

@cindex scripts

If you want to run multiple servers, the easiest way is to compile the servers

with different TCP/IP ports and socket files so they are not

both listening to the same TCP/IP port or socket file.

both listening to the same TCP/IP port or socket file. @xref{mysqld_multi}.

Assume an existing server is configured for the default port number and

socket file.  Then configure the new server with a @code{configure} command

get a list of some of the most important configurable variables in

@strong{MySQL}, including the socket name.

You should also edit the initialization script for your machine (probably

@file{mysql.server}) to start and kill multiple @code{mysqld} servers.

You don't have to recompile a new @strong{MySQL} server just to start with

a different port and socket.  You can change the port and socket to be used

by specifying them at run time as options to @code{safe_mysqld}:

shell> /path/to/safe_mysqld --socket=file_name --port=port_number

@end example

@code{mysqld_multi} can also take @code{safe_mysqld} (or @code{mysqld})

as an argument and pass the options from a configuration file to

@code{safe_mysqld} and further to @code{mysqld}.

If you run the new server on the same database directory as another

server with logging enabled, you should also specify the name of the log

files to @code{safe_mysqld} with @code{--log}, @code{--log-update}, or

If you want to use another database directory for the second server, you

can use the @code{--datadir=path} option to @code{safe_mysqld}.

@strong{NOTE} also that starting several @strong{MySQL} servers

(@code{mysqlds}) in different machines and letting them access one data

directory over @code{NFS} is generally a @strong{BAD IDEA}! The problem

is that the @code{NFS} will become the bottleneck with the speed. It is

not meant for such use. And last but not least, you would still have to

come up with a solution how to make sure that two or more @code{mysqlds}

are not interfering with each other. At the moment there is no platform

that would 100% reliable do the file locking (@code{lockd} daemon

usually) in every situation. Yet there would be one more possible risk

with @code{NFS}; it would make the work even more complicated for

@code{lockd} daemon to handle. So make it easy for your self and forget

about the idea. The working solution is to have one computer with an

operating system that efficiently handles threads and have several CPUs

in it.

When you want to connect to a @strong{MySQL} server that is running with

a different port than the port that is compiled into your client, you

can use one of the following methods: