@futureweb opened this Issue on November 15th 2018 Contributor

Hey there,
since a few weeks (not 100% sure if it started when we updated to 3.6.1 but it seems like?!) my "core:archive" Cronjob is giving me a nightly" [Zend_Db_Statement_Mysqli_Exception] Mysqli prepare error: MySQL server has gone away" ...

  • Cron is set to run hourly.
  • MariaDB isn't restarted or something (and no Errors)
  • no problems with Stats logging

From what I saw - it seems like sometimes the Cron is running into another long running "core:archive" Job which is causing troubles.

When this happens I see 2 long running SQL Threads doing:
OPTIMIZE TABLE piwik_archive_numeric_2012_01,piwik_archive_numeric_2012_02,piwik_archive_num...

Both waiting for "getting table lock" ... guess they stand out against each other ...
For now I try to extend Cron Times to 1.5 Hours and see if it helps ...

But woud it be possible to implement an "Archive Job already running" LOCK or something like that? Guess this should also help with such problems?

thx, bye from Austria
Andreas Schnederle-Wagner

@tsteur commented on November 15th 2018 Member

We have various locks to not archive the same site while another is in progress. This lock may not always work so we have another lock to not start archiving the same period/segment again while another archive is in progress (since Matomo 3.5 or so).

I don't know whether we have an Optimize Table lock but this could be actually quite helpful to prevent issues like this 👍

@tsteur commented on November 15th 2018 Member

A workaround be to disable optimize table in Matomo by setting [General] enable_sql_optimize_queries = 0 in the config/config.php and then running for example the command ./console database:optimize-archive-tables for example monthly. This is I reckon better in general anyway as it shouldn't be needed to optimize tables all that often.

@futureweb commented on November 16th 2018 Contributor

Hey @tsteur,
thank you for your fast answer!

Tonight it happened again:

Will disable optimize as advised by you and do it manually once a month - should be plenty enogh as you say! ;-)

Thank you, bye from sunny Austria

ps) I'm a bit puzzled that both OPTIMIZE Queries are running the exact same amount of time - it seems 1 Job triggered them both the same time?!? (got definitely only 1 archive cron on server)

@tsteur commented on November 22nd 2018 Member
@futureweb commented on November 22nd 2018 Contributor

sorry for not getting back on this ... disabling OPTIMIZE immediately helped on my issue - everything working as expected again! ;-)
Problem was definitely 2 OPTIMIZE TABLE Threads which somehow locked each other out ...
(which also prevented MySQL Backups - as they were not able to lock the Tables which were already locked by OPTIMIZE)

thx, bye from Austria

@tsteur commented on November 22nd 2018 Member

@futureweb I'll reopen the issue as we need to ideally add a lock there to not run this twice at the same time.

@otheus commented on February 4th 2021

As I wrote on the FAQ/feedback page:

We need to fix Matomo1 so that it sets the wait_timeout per connection. Setting the server variable is an ugly ugly hack that does not 'play well with others'. Moving from mysqli to pdo/mysql makes it even worse, since old mysqi at least allowed auto-reconnection. (Forums tell me, however, this feature has been deprecated). Further, the pdo-mysql driver does not allow (or is not documented to allow) config/connection parameters to be set via the DSN. Perhaps it is allowed, but it is not documented. The solution can be found here: https://stackoverflow.com/a/21403360/3849157 . The wait_timeout setting should either be as given above (28800) or better yet, configurizable in config.ini.

@Findus23 commented on February 4th 2021 Member

You could try adding the option here:

and report back if it changes anything. If it fixes the issue for you, it would be great if you could create a PR for this.

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