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Lost connection to MySQL server at, 'reading authorization packet', system error: 104 (or 0)


Hi all,

I'm very inexperienced mariadb/mysql/sql user/admin, but not totally clueless, been maintaining a tiny mysql DB for postfixadmin for years, then converted it to mariadb.

We recently started using SOGo (groupware). I hired the SOGo guys to help with the install/config, and have been using it trouble-free for a few months now (love it for the most part), until now.

Everything seems to be working fine, but since the upgrade to SOGo 2.2.4 on 6/12, which I am told increases the number of connections it uses to the DB, I have been getting very occasional errors like this (the system error is always either 104 or 0):

2014-06-12 03:30:15.530 sogo-tool[31674] ERROR: could not open MySQL4
connection to database 'sogo': Lost connection to MySQL server at
'reading authorization packet', system error: 104
<0x0x236c140[GCSChannelManager]> could not open channel
<MySQL4Channel[0x0x22241b0] connection=0x(null)> for URL:
<0x0x236c140[GCSChannelManager]>   will prevent opening of this channel
5 seconds after 2014-06-12 03:30:01 -0400
2014-06-12 03:30:15.531 sogo-tool[31674] Can't aquire channel

But it only happened once per day after the upgrade, then once it happened twice (about 12 hours apart), and it happened at times when the load would be the lowest (ie, 3:30am for the one above).

Googling reveals a lot of reports about this error over the years, some seemingly to be bugs, others DB tuning issues.

Should I be looking at tuning:

max_user_connections ?

If not, does anyone know where I should start looking? Is there some kind of extra logging I could enable that wouldn't cause serious performance problems?

Or... maybe this is simply not something I should be worried about?

Thanks for any help/suggestions...

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