[mythtv-users] recording not starting on time - one cause

Chris Isip cmisipster at gmail.com
Sun Dec 16 21:38:41 UTC 2007


On Dec 16, 2007 4:22 PM, John Drescher <drescherjm at gmail.com> wrote:

> On Dec 16, 2007 4:09 PM, Chris Isip <cmisipster at gmail.com> wrote:
> > In my effort to get rid of the ivtv buffers full errors in dmesg, I have
> > made a couple of conclusions.  Running optimize_mythdb.pl and backing up
> the
> > mythtv database will result in this error.   Furthermore, backing up the
> > myth database with mysqldump causes the server to be unresponsive for
> the
> > duration of the backup which means no playback possible on any frontends
> and
> > no recording will start.  The backend does not actually crash.  It seems
> any
> > playback or recording is "queued" and starts immediately after mysqldump
> > finnishes.  Hence the missing 8 minutes at the beginning of my
> recordings at
> > 1 AM.  Just thought I'd let the list know, in case somebody else is
> having
> > these problems.
> >
>
> Why not schedule this at 3:00AM or some other time that you know you
> will not be recording? The other way around this is to have the
> database on a second machine or even a different hard drive than the
> controller. Both of these database operations are very hard drive and
> interrupt intensive (because they end up causing a lot of hard drive
> thrashing) and the problem with that is that it ends up the you
> filesystem is not able to keep up with the datarate that ivtv needs.
>
> John
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I am actually testing a script right now that checks if there are any active
recordings  or playback  as well as any active jobs that mythshutdown is
able to monitor.   If there are none, then  do the  backup.  I time it to
happen at 40 1,2,3,4,5 * * * in cron (five attempts in the wee hours of the
morning, when there is no one using livetv).  A successful backup is
recorded and the script will not backup  more than once in a 24 hour
period.  Since the backup lasts about 8 minutes or so, starting it at 40
minutes means it will finnish before the start of the next hour and so
should't interfere with any future recordings.  This is an offshoot of the
mysql restart script I had to write because of a memory leak in mysqld.  I
have a similar script for optimize_mythdb.pl and it is set at 20 1,2,3,4,5 *
* * in cron.  Hopefully, between these, I would completely eliminate the
ivtv errors as well as the dropped minutes in recording.
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