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MySQL doesn't shutdown cleanly sometimes

Hi all,

I have a fresh install of Ubuntu 16.04 LTS Server x64 in a VirtualBox
VM with its provided MySQL, without any additional databases
currently. Sometimes the shutdown of MySQL itself fails with the logs
looking like the following:

> 2016-05-20T12:59:28.924585Z 0 [Note] InnoDB: FTS optimize thread exiting.
> 2016-05-20T12:59:28.924752Z 0 [Note] InnoDB: Starting shutdown...
> 2016-05-20T12:59:29.026037Z 0 [Note] InnoDB: Dumping buffer pool(s) to /var/lib/mysql/ib_buffer_pool
> 2016-05-20T12:59:29.026394Z 0 [Note] InnoDB: Buffer pool(s) dump completed at 160520 14:59:29
> 2016-05-20T13:00:29.872168Z 0 [Note] InnoDB: Waiting for page_cleaner to finish flushing of buffer pool

The last line is repeated all over again, but nothing seems to happen
anymore. If the shutdown of MySQL is initiated using SystemD, the
process is killed after 10 minutes, without SystemD e.g. using
mysqladmin it just hangs and seem to wait forever, at least a lot
longer than 10 minutes and the last sentence above is repeated all
over. One line per minute.

I've already googled regarding this message but couldn't find anything
that would resolve my problem: We didn't change any passwords from
their defaults in SystemD, we didn't "optimize" threading, we have no
I/O performance issue, there's exactly no load at all and MySQL itself
says that there are no dirty pages, and the problem doesn't occur
always, only pretty often. I guess around 1/3 of the time, in all
other cases the shutdown is fast and successful.

The problem occurred with an earlier installation of 16.04 beta release
and some databases loaded as well, so we decided to make a clean
install with the release sources and no databases to rule out as much
as possible. But now we have a somewhat default installation, the
problem still occurs and none of the tips on the web helps.

Additionally I had a hard time finding some more detailed information
about which files exactly are written and maybe even how, regarding
threading, flushing, problems with underlying I/O (SAS vs. SCSI vs.
SATA etc.).

Do you have any idea what else could be the problem or where I could
have a look at?

Our only workaround currently is killing the process after giving it
some time to flush, just like SystemD does, only that we don't
want/need to wait 10 minutes.


Mit freundlichen Grüßen,

Thorsten Schöning

Thorsten Schöning       E-Mail: Thorsten.Schoening@xxxxxxxxxx
AM-SoFT IT-Systeme      http://www.AM-SoFT.de/

Telefon...........05151-  9468- 55
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