[reSIProcate] asynchronous registration handling

[Justin Matthews]

Attached is the mod for asynchronous database handling.

There is a sequence/state diagram documented at
ServerRegistration::AsyncState.  

If there are no objections, I will add this to the main branch as it keeps
the existing logic intact.

Please have a look and send back any comments.

Thanks,

-justin


-----Original Message-----
From: Robert Backhouse [mailto:robertb at mxtelecom.com] 
Sent: Thursday, March 12, 2009 1:36 PM
To: Justin Matthews
Cc: 'resiprocate-devel'
Subject: Re: [reSIProcate] asynchronous registration handling

Hi Justin,

Thanks for your reply. I've still got a couple of questions (sorry if 
I'm missing something):

1. I presume you're suggesting that we reject the registration in 
RegistrationHandler::onXxx(). How does the information that the 
RegistrationPersistenceManager has failed reach the handler? The only 
way I can see is to keep a map from aor to status, provide a public 
interface to get at it, and cast the persistence manager to the 
appropriate subclass in order to decide whether to accept or reject the 
registration.

2. What happens if, say, there is a connection problem when we try to 
roll back to the previous registration details, or if we fail to take 
out the lock even (since the database is shared)?

It sounds as though your new implementation will make this a lot easier 
and clearer.

Thanks again,

Rob.


Justin Matthews wrote:
> Hi Rob,
> 
> Currently you would handle this by trapping all database failures in your
> persistence manager and then call ServerRegistration::reject().  All the
db
> operations are performance before the calls to
onRefresh,onRemove,onAdd,etc.
> If you reject() the registration, then ServerRegistration tries to roll
back
> the changes by removing the registration (via removeAor()) and then
> re-applying the original list that it saved (via addAor).
> 
> The implementation I am working on will allow more flexible error handling
> without blocking the DUM thread, will not require roll back if the
> registration is rejected and will require fewer DB calls.  I should have
> more details in a few days.
> 
> Thanks,
> 
> -justin
> 
> -----Original Message-----
> From: resiprocate-devel-bounces at resiprocate.org
> [mailto:resiprocate-devel-bounces at resiprocate.org] On Behalf Of Robert
> Backhouse
> Sent: Thursday, March 12, 2009 9:53 AM
> To: 'resiprocate-devel'
> Subject: Re: [reSIProcate] asynchronous registration handling
> 
> Hi,
> 
> I have a separate but related question. In the last few days I have also 
> been having trouble in this area while trying to implement a 
> database-based RegistrationPersistenceManager.
> 
> My problem is that there doesn't seem to be any mechanism to cope with 
> an action/query failing - if there is a problem with the database 
> connection, the SQL syntax, or just a random deadlock or transaction 
> timeout then I can't see a way to fail the registration.
> 
> I presume some people must have successfully written database backed 
> RegistrationPersistenceManager implementations - can anyone explain how 
> they dealt with SQL exceptions without a response to signify failure or 
> a suitable exception to throw?
> 
> Otherwise, if the ServerRegistration logic is being rewritten, do you 
> think this would be a sensible opportunity to support failures from the 
> RegistrationPersistenceManager in some way?
> 
> Thanks,
> 
> Rob.
> 
> 
>> 2009/3/9 Justin Matthews <jmatthewsr at gmail.com 
>> <mailto:jmatthewsr at gmail.com>>
>>
>> Hi,
>>
>> I am looking at adding asynchronous REGISTER handling in DUM. Has anyone 
>> thought about or actually implemented this?  There are some notes in 
>> DialogSet.cxx about moving REGISTER handling to DialogUsageManager, 
>> would these mean converting REGISTER handling to be a DumFeature?  Would 
>> this makes things easier to post back responses to a DUM feature as 
>> opposed to implementing some kind of postback to a ServerRegistration?

>>
>> Basically I need to send the DB queries off to another thread to avoid 
>> blocking.
>>
>> Also, is anyone else interested in this?
>>
>> Thanks,
>>
>> justin
> 


-- 
Robert Backhouse <robertb at mxtelecom.com>
Software Developer
Tel: +44 (0) 845 666 7778
Fax: +44 (0) 870 163 4694
http://www.mxtelecom.com
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