[mythtv-users] ringbuffer errors?

[Rich West]

Of course, MythTV decides to act up last night.. to the point where watching
a recording of the ball dropping was just not possible (I heard a LOT of "I
think this is the year we move away from mythtv!" from my other half).

The story goes that we set up ~5hrs of recording of one particular channel
to make sure we were able to watch the entire evening's worth of events (we
decided not to use livetv since that is sketchy to start with).  I canceled
all other recordings from 8pm through to 3am, so the only thing the backend
had to do was record and stream.  I even killed off the real-time commercial
flagger.

The symptoms we saw were the "Please wait..." black screen for >90 seconds
before it would start playing.  Skipping forward to near real time would
cause the video/audio to stop playing, and mythfrontend would become
unresponsive for a LONG time, eventually exiting the stream with a complaint
about the video buffers.  Going through that same process again, but not
skipping to real time did work, but it would randomly barf out again with
the same problem

The logs on the backend were showing the following ONLY when the frontend
was attempting to access the video.  Google searches show up similar errors
with varying resolutions (someone re-cabled the video cables for their
settop boxes, another re-formatted their drives, and yet another replaced
their drives.. the 'solutions' seemed unusually random):
2014-01-01 00:00:11.686894 I [1149/2045] ProcessRequest ringbuffer.cpp:1098
(WaitForAvail) - RingBuf(/video/1006_20140101030000.mpg): Waited 0.2 seconds
for data
                        to become available... 239926 < 753664

CPU usage & network usage on both the frontend and backend systems were
extremely low.  From that standpoint, they were basically bored.  Disk I/O
seemed fine (of course sysstat wasn't installed, and there was essentially a
revolt, so I couldn't dig too deep with the debugging), no disk errors
reported, and generally the backend appeared healthy (I graph everything via
cacti, including tuner usage, jobs, errors, etc).  I've never had issues
like this in the past, and we essentially did the same thing around
Thanksgiving (family over likes the football games) with great success. 
Needless to say, it was very frustrating, and I'm not sure where to even
begin looking..

-Rich