[mythtv-users] mythbackend not responding - and even more weirdness

Bill Arlofski waa-mythtv at revpol.com
Sun Dec 17 15:41:03 UTC 2006


brian wrote:
> Bill --
> 
>    I saw a similar situation here (running current SVN) a week or so
> ago.  mythweb, mythfrontend, and mythwelcome couldn't connect to the
> backend and all complained it may not be running.  Meanwhile, any
> scheduled recordings (and associated jobs such as commercial flagging)
> continued on as usual (more or less).  

Well, I guess I misspoke initially. In my case recordings don't take
place when the backend is not responding, but I do see commflagging jobs
come and go - or at least the database queries and mythbackend logs show
them checking to start - but since no new recordings have taken place,
no commflagging jobs need to run. :)

>    When I ran `top` via ssh on the myth server, I found that the
> mythbackend process was consuming 98+ % of the CPU, even when it should
> be "doing nothing".  I would shutdown/restart the machine and all would
> be well, for a while (maybe a day or so).

I had also seen that, but only ONE time. And since it was after a lot of
software updates on this box, I chalked that one up to the updates.
After the reboot, it has never done that since, so I am going to ignore
that in my case. :)


>    One of the guys in the #mythtv-users channel (GreyFoxx) suggested it
> may be related to a upnp issue, and that I try invoking mythbackend with
> the '--noupnp' parameter.  In my situation, this seems to have cleared
> up the issue -- I've not had that problem recur over the past week or
> so.

That is interesting, and something I am going to look into. The only
advice I got was from someone I can not remember telling me to "follow
instructions" and that "there are issues with mythtv .20 and MySQL 5" so
I dutifully exported my "mythconverg" and "mysql" databases, downgraded
MySQL to a 4.x version and imported the databases, and also had to
recompile PHP and qt against the downgraded MySQL.

Now I have been recently told that there really are no issues with
MythTV .20 and MySQL 5.x.   :-/

In any case, the database just keeps chugging along through all of this.

Thanks for the suggestion, Brian.



> On Sat, 2006-12-16 at 14:14 -0500, Bill Arlofski wrote:
>> Hello everyone. I just joined the list and I apologize for such a long
>> first post, but I am seeing such a strange set of issues so I will try
>> to include as much info right up front. Please bear with me. :)
>>
>>
>> Lemme try to explain:
>>
>> Everything works fine for a while, then randomly the mythbackend stops
>> responding to the frontend (and the Mythweb interface). But, mythbackend
>> is not 'hung'. It continues to query the MySQL database, and continues
>> to log to its own mythbackend.log. (nothing interesting jumps out at me
>> in that log though)
>>
>> The frontend will timeout and complain that the backend is gone, and of
>> course the "Watch Recordings" page and "Scheduled recordings" pages are
>> blank.
>>
>> But... here is the strange part: If I run strace without the -f (follow
>> child processes) I get this:
>>
>> # strace -s0 -p 26534
>> Process 26534 attached - interrupt to quit
>> futex(0x654618, FUTEX_WAIT, 2, NULL
>>
>> And it just sits there... and nothing changes in the frontend (which is
>> running in a window for easy monitoring).
>>
>> BUT if I run that same strace with the -f parameter, all of a sudden the
>> mythfrontend comes alive and is able to communicate with the backend and
>> the "Watch recordings" page is automatically populated and I can choose
>> a recording to watch and it works fine.
>>
>> When the strace -f process is killed, the mythfrontend again can no
>> longer communicate with the backend... Restart the strace -f and the
>> mythfrontend comes back to life and works perfectly again.
>>
>> Meanwhile, whenever the backend is not responding to the frontend, no
>> scheduled recordings take place, and the mythfrontend logs:
>>
>> 2006-12-16 13:48:24.328 Connecting to backend server: 192.168.254.4:6543
>> (try 1 of 5)
>> 2006-12-16 13:48:31.332 MythSocket(2aaab1cf1f50:34): readStringList:
>> Error, timeout (quick).
>> 2006-12-16 13:48:31.332 Unexpected response to MYTH_PROTO_VERSION:
>> 2006-12-16 13:48:31.332 ProgramList::FromScheduler(): Error querying master.
>>
>>
>> I know. This is very strange. I was just running strace to see what
>> mythbackend was trying to do when it was not responding to the frontend.
>> No idea why or how strace could affect how the backend process acts.
>>
>> Here are the system details:
>>
>> - Gentoo Linux
>> - AMD Athlon64 X2
>> - 2GB RAM
>> - # free
>>              total       used       free
>> Mem:       2059492    2035936      23556
>> -/+ buffers/cache:    1384692     674800
>> Swap:      1028000     436108     591892
>>
>> - Hauppauge Wintv-PVR500 dual tuner card
>> - ivtv version 0.8.1 (tagged release) loading
>> - Kernel Linux version: 2.6.18 SMP preempt mod_unload gcc-3.4
>> (I just noticed the preempt above. I thought I read somewhere NOT to use
>> that kernel option with MythTV... Could that be it?)
>>
>> - /mnt/store is an NFS mount with the following mount options:
>> remote_server:/mnt/store on /mnt/store type nfs
>> (rw,rsize=8192,wsize=8192,hard,intr,nfsvers=3,actimeo=0,addr=192.168.254.3)
>>
>> - Filesystem on remote server is jfs
>> - MySQL database is v4.1.22
>> - mythbackend --version reports:
>> Library API version: 0.20.20060828-3
>> Source code version: exported
>> Options compiled in:
>>  linux release using_lmsensors using_v4l using_oss using_alsa using_ivtv
>> using_firewire using_x11 using_xv using_xrandr using_opengl_vsync
>> using_opengl using_frontend using_backend using_bindings_perl
>>
>> - $ mythfrontend --version reports:
>> 2006-12-16 13:40:20.588 Using runtime prefix = /usr
>> 2006-12-16 13:40:20.597 DPMS is disabled.
>> 2006-12-16 13:40:20.629 New DB connection, total: 1
>> 2006-12-16 13:40:20.637 Connected to database 'mythconverg' at host:
>> localhost
>> 2006-12-16 13:40:20.639 Total desktop dim: 1680x1050, with 1 screen[s].
>> 2006-12-16 13:40:20.644 Using screen 0, 1680x1050 at 0,0
>> Library API version: 0.20.20060828-3
>> Source code version: exported
>> Options compiled in:
>>  linux release using_lmsensors using_v4l using_oss using_alsa using_ivtv
>> using_firewire using_x11 using_xv using_xrandr using_opengl_vsync
>> using_opengl using_frontend using_backend using_bindings_perl
>>
>> Neither processor ever has more than a 20% utilization - both fluctuate
>> anywhere between 0 and 20 and this is with other apps opened and
>> running. Also system load sits around 0.6 so there are no system loading
>> issues. :-/
>>
>>
>> ANY and ALL thoughts are appreciated. I would be willing to provide any
>> additional information to help resolve this issue.
>>
>> BTW, from what I have seen so far MythTV is pretty awesome. Nice job
>> devs!  :)
>>
>> --
>> Bill Arlofski
>> Reverse Polarity
>> waa-mythtv at revpol.com



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