[reSIProcate] dum shutdown issues (IMPORTANT)

[Jason Fischl]

Someof the changes I've made to dum as part of my shutdown-related changes:

added a pure virtual BaseUsage::end() so the HandleManager can end any 
usages that are still kicking around. Note that end() is now void and 
does not return the SipMessage&. This necessitated a number of changes 
to the derived Usage code. It will also require some minor changes to 
application code.

Jason



Jason Fischl wrote:

> Hi all,
>
> After fighting with shutdown for an entire day, I'd like to propose 
> some changes. Here are the current issues:
>
> Shutting down a useragent requires us to:
> - async end all active usages
> - async shutdown call to DialogUsageManager
> - async shutdown call to SipStack
> - async end the StackThread (if we are using one)
>
> The application is required to somehow coordinate all of these 
> requests to shutdown and wait for appropriate callbacks before moving 
> on to the next one.
>
> There is no way to request dum to shutdown all usages. The order of 
> usage termination may be important for some applications. For 
> instance, some applications may require the registrations to be ended 
> last since they may have GRUUs bound to them. In other cases, the 
> order of unPUBLISH vs unSUBSCRIBE may also be important.
>
> In the current implementation, if the application calls shutdown and 
> there are active usages, dum will wait for those usages to all end and 
> will then call the handler onDumCanBeDeleted. However, if there are 
> active ClientSubscriptions and dum never receives  NOTIFY messages 
> with SubscriptionState == Terminated, dum will never exit. This can 
> happen if the presence server crashes.
>
> Proposed changes:
> - SipStack should be owned by DialogUsageManager. Is there really any 
> case where the application would want to reuse a SipStack object after 
> shutting down the dum?
> - Application should be able to shutdown without having to explicitly 
> end all active Usages. Either dum should end the usages or it should 
> be able to shutdown without ending them. Either way, it should not 
> leak memory.
>
> Current Interface:
>
> void
> DialogUsageManager::shutdown(DumShutdownHandler* handler);
>
> virtual void
> DumShutdownHandler::onDumCanBeDeleted()=0;
>
>
> Proposed Interface:
>
> // In all cases, no leaks (obviously :)
>
> // End usages in the following order:  ServerInviteSession, 
> ServerSubscription,  ClientInviteSession, ClientSubscription,
> // ClientPagerMessage, ClientPublication, ClientRegistration
> // call DumShutdownHandler::onDumCanBeDeleted when all usages are 
> ended, SipStack is ended and StackThread is shutdown
> // After giveUpSeconds, exit regardless. If giveUpSeconds == 0,  wait 
> indefinitely
> void DialogUsageManager::shutdown(DumShutdownHandler* handler, 
> unsigned long giveUpSeconds=0);
>
> // call DumShutdownHandler::onDumCanBeDeleted when all usages are 
> ended, SipStack is ended and StackThread is shutdown
> // After giveUpSeconds, exit regardless. If giveUpSeconds == 0,  wait 
> indefinitely
> void DialogUsageManager::shutdownIfNoUsages(DumShutdownHandler* 
> handler, unsigned long giveUpSeconds=0);
>
> // Shutdown immediately - ignore existing usages.
> // call DumShutdownHandler::onDumCanBeDeleted when all usages are 
> ended, SipStack is ended and StackThread is shutdown
> void DialogUsageManager::forceShutdown(DumShutdownHandler* handler);