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

Bill Arlofski waa-mythtv at revpol.com
Sat Dec 16 19:14:38 UTC 2006


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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