[mythtv-users] Guide updates for CBS and TNT this evening

[Michael T. Dean]

On 11/17/2015 02:55 PM, Robert Eden wrote:
> On 11/17/2015 1:38 PM, R. G. Newbury wrote:
>> The grabber time settings are on the last (eighth) sub-page of the 
>> GENERAL pages of mythtv-setup. The user enters the name of the 
>> grabber program or script, and can either set the start and end times 
>> for the grabber 'window', or select to let the system use the time 
>> suggested by mythtv.
>>
>> A screen-shot is annexed, but I think it will get stripped from the 
>> list publication.
>
> Geoff, I saw your pic.. it made it to the list.
>
> What happens if the suggested time is outside the 1 hour window you 
> have configured?

If "Run guide data program at time suggested by the grabber" is enabled, 
MythTV completely ignores the specified "Guide data program execution 
start" and "Guide data program execution end" (run window).  Ideally in 
the setup screen, the start/end window options would be grayed out or 
hidden when suggested time is enabled, but setup hasn't gotten much love 
for years.

> The MythTV "bug" occurs when the download doesn't occur normally. The 
> nightly cleanup code (at 2am) says "hey I haven't downloaded data 
> recently" and does it. *Everyone* has 2:00am for the nightly cleanup job.

The MythTV "housekeeper" is started immediately upon mythbackend startup 
and checks every 5 minutes whether jobs (including a run of 
mythfilldatabase) should be executed.  The mythfilldatabase run is set 
as a daily task (for the master backend, only), so if--at the time the 
check is performed--it has been at least 24 hours since the last 
successful run of the job, the housekeeper will run the job (if there 
was an unsuccessful attempt to run it, it's identical to it not having 
been run, however the housekeeper will not run the job again if the 
"unsuccessful--or not yet successful--job is still running--meaning if 
it takes longer than 5mins, MythTV won't start it again).  There is no 
code in MythTV for a 2am nightly cleanup job.  The closest thing is 
probably the fact that a daily job will be forced to run within 30 
minutes before midnight if it has not yet run that day.

Even a brand new install of MythTV with all default values should 
randomize mythfilldatabase runs sufficiently.  MythTV, by default, is 
set to automatically update program listings at the time suggested by 
the grabber.  Even if a user disables the option to run at the time 
suggested by the grabber, the default values for the guide data program 
execution start/end are 0/23 (meaning it is allowed to occur at any time 
during the day).  So, to get a 2am spike, the user would have to 
explicitly disable running at the time suggested by the grabber and 
explicitly set an execution window starting at 2--but even then, the 
spike wouldn't be exactly at 2:00, but would be "spread out" within a 
5-minute window of 2:00-2:05. However, if the user disabled the option 
to automatically update program listings (i.e. disabled mythbackend's 
running mythfilldatabase), they could run it at whatever time they chose.

So, I would say that the 2am spike is due to people/distros 
misconfiguring systems and disabling "Automatically update program 
listings" and scheduling a cron job to run at 2am.  I don't know if some 
(or most? or all?) distros tend to set up their crontabs so that 
/etc/cron.daily/ jobs are run at 2am, but if so, perhaps some distro(s) 
is throwing a script to run mythfilldatabase (or to run it if the script 
thinks it hasn't been run recently--meaning that the distro doesn't 
trust mythbackend to do the job right) in /etc/cron.daily/.  Regardless, 
since there's no magic 2am time in any of MythTV, whatever causes the 
spike is outside of MythTV--at least outside of 
https://github.com/MythTV/mythtv/tree/master/mythtv (meaning some 
distros may be putting in some 2am hard-coded time in a patch, but I 
don't know of any, and don't see any in 
https://github.com/MythTV/packaging ).

Mike