PQM silent branch lossage

[John Arbash Meinel]

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Barry Warsaw wrote:
> Hi Robert and friends,
> 
> As you know, we rely on PQM for Launchpad development, and for a while
> now it's been the case that branches can get silently dropped.  There's
> a lot of speculation about why this happens, and there's this open bug
> on PQM:
> 
> https://bugs.edge.launchpad.net/pqm/+bug/246660
> Silently drops branches in unknown formats
> 
> I've heard rumors that PQM can also silently drop branches due to
> autopacking bugs, but I really don't know much about the details of
> this.  I'm sure there is more than one reason for silent branch loss.
> 
> The purpose of this thread is to try to gather all known information
> about why branches get silently dropped.  Ideally, this should never
> happen, and the submitter should always get a success or failure message.
> 
> If you know (or think you know) a reason for merges getting silently
> dropped, please follow up to this message.  I'll be happy to submit bug
> reports for known issues, if you don't beat me to it.
> 
> Thanks,
> -Barry
> 

Well, the man to ask, of course, is Robert and now Daniel who is poking at the
code. And just look at all the places where PQM can error out before getting
to the point of saying you are a failure... :)

I think it can be as easy as doing something like (pseudocode):

try:
  handle_request()
except:
  exc_info = sys.exc_info()
  send_email('failed because of exception: %s' % (exc_info))

The idea is to just wrap a big catch-all-and-send-a-failure-message safety net.

Note that stuff like "accepting merge directives" makes it less likely to hit
this sort of thing, but it still seems like good practice to do this.

Then again, you can't *quite* do this, because until you've processed some of
the request, you don't have enough info to know who to send to. That, and I
think by design he wanted invalid (by gpg, or whatever) to just get ignored,
rather than having someone spam the PQM with invalid requests cause a DOS.

John
=:->
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