[mythtv-users] after update frontend hangs burning 100% of CPU

Michael T. Dean mtdean at thirdcontact.com
Mon Apr 1 11:38:57 UTC 2013


On 04/01/2013 12:11 AM, D. Hugh Redelmeier wrote:
> [This might or might not be related to "update failed now fe crashes".]
>
> I updated a mythbuntu system from MythTV 0.25 to 0.26.  The Ubuntu is
> 12.04 LTS.
>
> I've never done a MythTV update before, only a very few reinstalls.
>
> Procedure:
>
> 0) backup the myth database

> 7) the backend seemed to hang.  After a few minutes I rebooted.
>     Now I know that the backend wasn't hung, it was just changing the
>     databse to the new schema.  After the reboot, it seemed to
>     continue from where it left off.

If you ever have a "failure" (or stop/kill mythbackend) during a 
database schema upgrade, you should always restore the backup you made 
in step 0 (one at the old schema version that has never had an upgrade 
attempted), then start over and let the upgrade occur without 
interruption.  If you don't, you may have corruption in either the data 
or the schema.  So, I would recommend restoring the backup and re-doing 
the database upgrade.

Also, it's always recommended to run mythtv-setup first (with no other 
MythTV applications running) after doing an upgrade.  It will perform a 
database upgrade for you (and actually tells you its doing so--though it 
doesn't tell you anything more after it starts and just shows a blank 
screen while it's upgrading) and when the UI appears, you can then check 
to see if you need to change any of the new settings.

> 8) I started the frontend (normally I don't run it on this machine).
>     It seemed to hang.  The display was completely blank.
>
>     The backend was actually doing a database backup (why is
>     that the frontend's job?).

Frontend plugins do database updates for themselves--the backend has no 
idea what plugins you have, let alone how their database schemas work.

>     After finishing the backup, the frontend hung, with no display,
>     using 100% of one CPU core.
...
> 9) I repeated (8) a couple more times.  Results were the same, including
>     doing yet another database backup each time (wasn't the previous
>     one good enough?).

That means that something still hasn't finished doing a database update 
(the logs will tell you what).

I'm guessing you're cutting off some major database update for some 
plugin.  So, you need to go back to the step 0 pre-upgrade database and 
start the upgrade process over.

> Note: MythWeb seems to work from another machine.  New recordings are
> happening.  So lots of this system is working.

Which means that the backend database upgrade completed successfully.  
I'd still recommend that you go back to the pre-upgrade database and  
start the DB upgrade process over.  Unfortunately, you'd need to take 
the new recordings (which you can find with 
http://www.mythtv.org/wiki/Find_orphans.py ) and put them in Video 
Library to make them available to watch with the 
properly-upgraded-from-an-older-backup database.

Mike


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