[asterisk-app-dev] ARI Early Bridge Development: Call Forwarding

[Mark Michelson]

Hi folks,

You may recall that I sent an e-mail [1] out about a month ago saying 
that I was working on implementing some new ARI methods for Asterisk 14 
that would allow for bridging calls early, the idea being that this 
would allow for situations like allowing early media to be bridged to 
callers. What I have created so far are two new ARI methods: one that 
creates a new channel, and a second that dials that channel. You are 
free to place the newly created channel into a bridge and then dial it, 
or you can create the channel, dial it, and then add it to the bridge 
based on some channel state change (like if it starts ringing). I've got 
basic operations working really well right now, and now I'm 
investigating the more interesting corners of the feature.

This has led me to an issue regarding call forwarding. In the interest 
of brevity, I'll just say that call forwarding does not play well with 
ARI's threading when it comes to bridged channels. I fear that 
attempting to handle call forwards automatically within Asterisk will 
require jumping through some hoops resulting in the potential for errors 
to occur.

I would like to propose a solution to this. Instead of having Asterisk 
automatically handle call forwards when performing an ARI dial, raise an 
event stating "Outbound channel X wants to forward the call to Y". This 
way, the ARI application writer can act on this event as desired. You 
can ignore the call forward attempt altogether. You can look up who Y is 
and forward the call manually. You can check some presence database and 
forward to Y's voicemail instead of Y. You can say "screw you X" and 
forward the call to Z instead.

The upsides to this are that
1) It places the ARI author in complete control of the destination of 
the call. Automatic behavior from Asterisk is limited, and there will be 
no surprises.
2) By always dialing outbound calls from the ARI application, we can 
assure that channels are being tracked as expected and there are no 
hoops that we have to jump through internally to ensure that everything 
is set up properly.

The big downside I can think of is that the current ARI originate 
command does automatically perform call forwards. This would introduce 
an inconsistency in the behaviors of the two methods of making outbound 
calls.

What is the list's opinion on the proposal for handling call forwards in 
the new ARI dial command?

Thank you very much,
Mark Michelson

[1] 
http://lists.digium.com/pipermail/asterisk-app-dev/2016-March/000769.html