[asterisk-app-dev] ARI ApplicationActivated event?

[Joshua Colp]

Ben Merrills wrote:
>> Kevin Harwell wrote:
>>
>> <snip>
>>
>>> So then there are for sure cases where full state is not
>>> recoverable and a missed message(s) playback mechanism would be
>>> ideal. I guess the questions go back then to how useful is it and
>>> is it worth the effort?
>> I think, depending on the application, it's useful.
> [skrusty] I think the approach here is wrong. Asterisk shouldn't be
> buffering these messages or worrying messages have not been received
> (as such). When we reviewed (with some other community members)
> improving reliability and fault tolerance, the main strategy seems to
> be queue those messages and distribute them over multiple
> applications serving ARI.
>>> Right now Asterisk doesn't even notify an application that it is
>>> in a "reactivated" state.  So either applications currently built
>>> on ARI don't care about syncing state on reconnection, or they
>>> use the current commands available to do it (and that is
>>> sufficient).  Maybe having the proposed extra notification would
>>> not be so useful.
>> I think right now this hasn't been run into enough to really be a
>> substantial problem for people.
> [skrusty] True, it's not, but it has been considered. The idea of
> proxying those messages from a locally hosted service into a queue of
> some sorts seems to work best so far. This method solves issues
> dealing with high availability and failover.

This isn't trying to solve high availability and failover. As you've 
said there are ways to do that. This is "I have a standalone 
application. It crashes and restarts. I had channels in it. How do I 
recover?". As it is those channels are lost to the application but still 
remaining up, unless the application maintains its own state. That's a 
bad spot to be in. IMO saying to deploy an external message bus with a 
proxy and to persist state in an outside mechanism is not a very good 
answer to that for people who are trying to do simple things.

Maybe the solution is that upon reconnection if any channels remain in 
the application you get an event with their ids. This reduces how much 
the application has to do (and in fact if they don't want to store state 
they can hang them all up and start fresh). It's also information we 
already have.

-- 
Joshua Colp
Digium, Inc. | Senior Software Developer
445 Jan Davis Drive NW - Huntsville, AL 35806 - US
Check us out at: www.digium.com & www.asterisk.org