MySQL Bugs: #52688: confusion in STATUS CHECK COMMAND

Bug #52688	confusion in STATUS CHECK COMMAND
Submitted:	8 Apr 2010 12:11	Modified:	6 Feb 2013 18:53
Reporter:	Susanne Ebrecht	Email Updates:
Status:	Not a Bug	Impact on me:	None
Category:	MySQL Workbench: Administration	Severity:	S3 (Non-critical)
Version:		OS:	Any (Linux)
Assigned to:		CPU Architecture:	Any

Description:
Look into CREATE NEW SERVER INSTANCE PROFILE

You have a field there called STATUS CHECK COMMAND

per default there is given ps -C mysqld -o pid=

I just run this command in my shell:

$ ps -C mysqld -o pid=
22740
28985

As you can see I got two results.

It is because two servers are running.

Suggestion:

Better would be:

less /PATH_TO_MYSQL_DATA_DIR/<hostname>.pid

How to repeat:
Run two mysqld on same machine.

Run the given ps command.

Suggested fix:
See above

datadir of mysql is usually not world readable, so checking the pid file is not the best option.
Also we need reasonable defaults and datadir very often changes between installations, so the user would have to modify the default settings anyway, so the provided suggestion doesn't seem practical.

In case the user has more than one instance of MySQL running, it is expected the user is more or less knowledgeable and will take care to update the server instance profile accordingly, so that each profile 
matches the desired instance through whatever method they want.

If the user does have >1 instance of mysql running and the status check command is left in the default, there is no bad side effect, except for the fact that the status detection will be unreliable.

I'll mark it QA, but I think this should be marked Not a Bug

With KDEs default PIM application Akonadi now starting a "private" mysqld instance [1,2] the the theory that 

  In case the user has more than one instance of MySQL running, 
  it is expected the user is more or less knowledgeable and will 
  take care to update the server instance profile accordingly ...

no longer holds. A KDE user may easily end up with two running
mysqld instances (or even more on a multi user machine) without
even knowing that there are such extra instances.

[1] http://techbase.kde.org/Projects/PIM/Akonadi#Do_I_need_a_running_MySQL_server.3F
[2]  http://techbase.kde.org/Projects/PIM/Akonadi#Why_not_use_MySQL.2FEmbedded.3F

Bug #54027 is set as duplicate of this bug here.

Suggest changing default command in profile to:

ps u -C mysqld |grep datadir=/var/lib/mysql

This is about the same as the current setting, except the user can easily see that the datadir is being checked and hopefully realize they have to update it.

Marked bug #53788 as duplicate of this one