Python BEConnection:backendCommand timeout too low and improper protocol implementation

[angela.schmid@…]

I use lossless_cut to export recordings to the video library which half of the time crashed:

CRITICAL - Export to MythVideo?, aborting script.

Error: invalid literal for int() with base 10:

The problem occurs only when the video disk had to spin up.

The root cause is a too low timeout of 10 seconds in the Python BEConnection class when calling QUERY_FILE_EXISTS.

I could identify the following problems:

lossless_cut 
which calls dataheap.py Video:open()
which calls mythproto.py ftopen(), can not provide a timeout, because the logic to use a backend is in the next method
which calls mythproto.py, path = FileOps(host, db=db).fileExists(filename, sgroup)
which calls mythproto.py backendCommand(), fileExists calls backendCommand and should provide a higher timeout.
which calls connections.py BEConnection:backendCommand(), with default timeout=10seconds

• A user application can not provide a higher timeout.
• fileExists calls backendCommand and should provide a higher timeout.
• BEConnection:backendCommand() should use a higher default timeout.

The exception is misleading and caused by *not* throwing a proper exception, when hit by a timeout:

BEConnection.backendCommand:
    if len(select([self.socket],[],[], timeout)[0]) == 0:
       # no data, return
       return u''

• The client application receives an empty string, instead of a response described in ​https://www.mythtv.org/wiki/QUERY_FILE_EXISTS_(Myth_Protocol) or an exception.
• "no data, return empty string", is there really such a response from the backend in the Myth protocol?

[Stuart Auchterlonie]

We have moved all bug tracking to github [1]

If you continue to have this issue, please open a new issue at github, referencing this ticket.

[1] - ​https://github.com/MythTV/mythtv/issues