[mythtv-users] ExternalRecorder - Errno 11

[Marc Rawji]

On Tue, Nov 21, 2017 at 11:11 PM, Stephen Worthington <
stephen_agent at jsw.gen.nz> wrote:

> On Wed, 22 Nov 2017 06:03:31 +0000, you wrote:
>
> >Hi Everyone,
> >
> >I've been working on an external recorder for a while. It works most of
> the
> >time, but recently i've been getting new errors.
> >
> <snip>
> >My problem below is that I am getting a "Resource temporarily unavailable
> >(11)" when mythtv is trying to read from the stdin (the stdout of my
> >program with the video stream)
> >
> >This seems to happen from this call:
> >https://github.com/MythTV/mythtv/blob/master/mythtv/
> libs/libmythtv/recorders/ExternalStreamHandler.cpp#L125
> >
> >The STDIN stream is configured to be non blocking, so the errno 11 isn't
> >unexpected:
> >https://github.com/MythTV/mythtv/blob/master/mythtv/
> libs/libmythtv/recorders/ExternalStreamHandler.cpp#L343
> >
> >I am not sure what to change to keep this from happening.... it fails
> about
> >50% of the time, which is annoying.
> >
> >I am looking for advice on a fix, or how to troubleshoot. I am running
> 0.29
> >on Ubuntu 16.04.
> >
> >Thanks!
> >Marc
> >
> <snip>
>
> If I am reading the ExternalStreamHandler.cpp.ExternIO::Read function
> correctly, then the only way that can happen is if your stdout stream
> indicates that it has data buffered and available to be read (the
> poll() call from the Ready() call says there is data there), but then
> your stdout fails to provide that data when it is called from read().
> The most obvious reason I can think of for that would be if your code
> was slow in responding to the read(), due to some unforeseen
> circumstance such as garbage collection or being swapped out at the
> time.  But I would have thought that your stdout buffer would have
> been there waiting to be read, rather than any higher code needing to
> be run to provide the data.  Are you using buffered I/O on your
> stdout?
>
>
Thanks for the quick reply Stephen. I am going to very quickly expose my
ignorance on how these FDs work. (just setting expectations)

Yes, I am using buffered output, specifically a BufferedWriter in Python (
https://docs.python.org/2/library/io.html#io.BufferedWriter). I added
explicit "flush" commands after the 'write' command, but it didn't help.

I'll try dropping the buffered output tonight and see what happens. I
didn't think that using a buffered writer would affect how data is present
in the stream.

Thanks,
Marc
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mythtv.org/pipermail/mythtv-users/attachments/20171122/d987c60f/attachment.html>