The reliability of python threads

[Carl J. Van Arsdall]

Aahz wrote:
> [snip]
>
> My response is that you're asking the wrong questions here.  Our database
> server locked up hard Sunday morning, and we still have no idea why (the
> machine itself, not just the database app).  I think it's more important
> to focus on whether you have done all that is reasonable to make your
> application reliable -- and then put your efforts into making your app
> recoverable.
>   
Well, I assume that I have done all I can to make it reliable.  This 
list is usually my last resort, or a place where I come hoping to find 
ideas that aren't coming to me naturally.  The only other thing I 
thought to come up with was that there might be network errors.  But 
i've gone back and forth on that, because TCP should handle that for me 
and I shouldn't have to deal with it directly in pyro, although I've 
added (and continue to add) checks in places that appear appropriate 
(and in some cases, checks because I prefer to be paranoid about errors).


> I'm particularly making this comment in the context of your later point
> about the bug showing up only every three or four months.
>
> Side note: without knowing what error messages you're getting, there's
> not much anybody can say about your programs or the reliability of
> threads for your application.
>   
Right, I wasn't coming here to get someone to debug my app, I'm just 
looking for ideas.  I constantly am trying to find new ways to improve 
my software and new ways to reduce bugs, and when i get really stuck, 
new ways to track bugs down.  The exception won't mean much, but I can 
say that the error appears to me as bad data.  I do checks prior to 
performing actions on any data, if the data doesn't look like what it 
should look like, then the system flags an exception.

The problem I'm having is determining how the data went bad.  In 
tracking down the problem a couple guys mentioned that problems like 
that usually are a race condition.  From here I examined my code, 
checked out all the locking stuff, made sure it was good, and wasn't 
able to find anything.  Being that there's one lock and the critical 
sections are well defined, I'm having difficulty.  One idea I have to 
try and get a better understanding might be to check data before its 
stored.  Again, I still don't know how it would get messed up nor can I 
reproduce the error on my own. 

Do any of you think that would be a good practice for trying to track 
this down? (Check the data after reading it, check the data before 
saving it)



-- 

Carl J. Van Arsdall
cvanarsdall at mvista.com
Build and Release
MontaVista Software