[asterisk-dev] application errors

[Tilghman Lesher]

On Monday 29 October 2007 20:25:05 Moises Silva wrote:
> On 10/29/07, Dmitry Andrianov <dimas at dataart.com> wrote:
> > Need an advice or something regarding the issue 10815 -
> > SendFAX/ReceiveFAX applications. Much like as their ancestors
> > (txfax/rxfax), these applications return -1 in case of any problem with
> > the channel. As I understand negative result immediately aborts dialplan
> > execution. However, people are asking to add FAXSTATUS channel variable
> > set by the application which will indicate if transmission was successful
> > or not. But again, in case of any error, application returns -1 so there
> > is no sense in setting any variable because no one will be able to review
> > it.
> >
> > At the same time I understand people who may want to know if fax was sent
> > or not. The only way to satisfy them I see is to ALWAYS return zero from
> > the application to let dialplan execute (and setting FAXSTATUS with
> > something indicating error). The problem is that I haven't seen any
> > application in the Asterisk which returns zero always - even in the case
> > of channel hangup etc, reporting failures by means of channel variables.
> > So creation of such application can be considered a bad practice.
> >
> > So the question is - what is the best (or recommended) approach here?
>
> I don't see any problem with returning 0 and setting FAXSTATUS. I have
> not checked for other applications *ALWAYS* returning 0. However I
> don't think it matters that much. If sending a fax fails, it is
> understandable that people want to do something else in the dial plan,
> so aborting dial plan execution is not the way to go. Set FAXSTATUS
> and move on :)
>
> As I understand returning -1 is reserved for calling the application
> without the proper arguments or stuff like that. Note that Asterisk
> parser does not check for applications being called with the proper
> arguments (given arguments complexity), so, checking inside and
> returning -1 is the way we have to indicate a flawed dial plan.

Returning -1 is a method of ensuring the channel gets ended properly.
In the case of receiving a fax, there usually isn't a person on the line who
can continue the call in any meaningful way, so returning -1 ensures that
the channel hangs up.

However, I would recommend that the FAXSTATUS variable still be set,
as it can be checked in the "h" extension.

-- 
Tilghman