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Re: mysqld_multi




Hello Matthew,

On 5/19/2017 12:19 PM, Matthew Black wrote:
I just installed MySQL Enterprise Edition 5.7 on RHEL 6.8 to replace an aging 5.1 system running on RHEL 5. We run mysqld_multi with multiple instances, each database on its own TCP Port 33xx. I'm having trouble creating a database on the new server in a multi environment.



Can anyone provide a simple example of how to edit /etc/my.cnf file and command line steps necessary for creating a new database running on, for example, port 3311?



Thanks in advance.



matthew


How to use mysql_multi is covered in the Manual. This includes a sample my.cnf file demonstrating how to define your separate instances.
https://dev.mysql.com/doc/refman/5.7/en/mysqld-multi.html

However, before you setup an instance to be managed by mysqld_multi, you will need to instantiate a set of datafiles for that 5.7 instance of the mysqld daemon to manage. You do that following the directions here (by hand) the first time.
https://dev.mysql.com/doc/refman/5.7/en/data-directory-initialization.html

This means you need to setup at least two folders (one for --datadir and one for --tmpdir) for each separate instance you want to create and assign ownership and privileges to those folders appropriate to the user your mysqld daemon will be executing as when it runs. There are other things you must also keep unique between instances when they share a common host machine. Those are described here:
https://dev.mysql.com/doc/refman/5.7/en/multiple-servers.html

An example of setting up the folders and assigning privileges to them is located in the instructions to installing a set of mysqld binaries using a .zip or .tar archive. Please note, you do not need a separate mysqld installation for each instance you want to create. Several daemons (each operating on their own port, socket, folders, data files,... ) can be started using just one set of binary files.
https://dev.mysql.com/doc/refman/5.7/en/binary-installation.html

So... the general process would look like this (presuming you have already installed mysqld and setup at least one instance)
==

1) Decide where you want a second (or later) instance to store its files. Choose port numbers and unix socket names for this new instance that are unique from any other instances that will be running on this host.

2) Setup any new folders you need to create (including assigning privileges)

3) Document those names and any other settings you want this additional instance to use in a configuration file specific for this instance

4) Use that special configuration file to bootstrap (initialize) the data files used to manage that instance (the --initialize instructions were linked to earlier in this reply)

5) Once you have this instance setup the way you want. Shut it down.

6) Copy the elements that are unique to this instance into an appropriately-named section of your common configuration file (the one that mysqld_multi will read)

7) Test that you can start/stop this new instance using mysqld_multi

As you can tell, it takes a bit of planning and effort to establish a non-default setup of hosting multiple MySQL instances on the same host machine. There is no simple one-line command to tell mysqld_multi to create a new instance as there are things it cannot do (like create folders in your file system).

Regards,
--
Shawn Green
MySQL Senior Principal Technical Support Engineer
Oracle USA, Inc. - Integrated Cloud Applications & Platform Services
Office: Blountville, TN

Become certified in MySQL! Visit https://www.mysql.com/certification/ for details.

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