Re: Very slow reconnection to medm after IOC reboot

[Andrew Johnson <anj@aps.anl.gov>]

On Friday 23 January 2009 16:40:22 Jeff Hill wrote:
> But perhaps this would work just as well (with very fast reconnect times)
>
> O rebuild the application
> O reboot the IOC

Unfortunately on Windows this is not possible; installing a new version of 
a .DLL or .EXE is not permitted by the OS until all programs using it have 
quit, thus one has to stop the IOC before the rebuild can be started.

> Nevertheless, if by chance one ends up with the first scenario, restarting
> the MEDM screen isn't, from my perspective, exactly heavy lifting -
> considering that we are presumably waiting at the edge of the seat for the
> channel's to reconnect. Synchronization might be the primary aggravation,
> but perhaps it will even be successful the first try if one waits
> approximately long enough for the IOC to finish rebooting before restarting
> the medm screen.

For the moment that does appear to be Mark's only alternative to waiting the 4 
minutes, but this is not an acceptable long-term solution (and contrary to 
what you say below, this needs to be fixed in R3.14 since it got broken in 
R3.14).  I'd like to have a discussion (on core-talk or at the codeathon) 
about other reconnection algorithms that could be used to fix this while 
still protecting the network from the UDP storms that we used to get.

> I am busy with other projects at the moment, but perhaps you might consider
> creating a mantis entry (we want to minimize changes to R3.14 so this would
> be against R3.15) describing the problem (and including a copy of this mail
> exchange), and perhaps some improvements can be made (within the
> constraints of reliable operation of course).

I have filed Mantis bug #330 which refers to this tech-talk discussion thread 
for the details.

- Andrew
-- 
The best FOSS code is written to be read by other humans -- Harold Welte