[Asterisk-Users] Multiple AGI Issues

[Douglas Garstang]

Freddi,

I started out this morning try to proof the concept of having Asterisk call an AGI script, set several variables, and then return control to the dialplan where it would execute the command. I wanted to set a number of variables in the AGI for each number to dial. The first variable would be the command to execute, for example "Dial" or "Macro". The format of this variable name would be NUM1_CMD, NUM2_CMD, ..., NUM5_CMD.

Every single time I try to do anything even remotely complex in the Asterisk dial plan I hit a brick wall. This is one of the major reasons I wanted to put EVERYTHING into an AGI script. It seems to have some serious limitations that make it unusable except for the most trivial tasks. Take the variables above for example, I wanted to loop through these...

exten => s,1,Set(mainLoop=1)
exten => s,2,While($[${mainLoop} < 6])

exten => s,3,GotoIf($[ "${NUM$mainLoop_CMD}" = "Dial" ]?5:7)
exten => s,4,Macro(CommandDial)
exten => s,5,Goto(20)
...

Take a look at priority 3. You'll notice I was trying to 'construct' the variable name from the loop variable. This would even work in a shell script, but it doesn't in Asterisk. Seems I have to not use a loop, and reproduce the same code each time, once for each number in the findme/followme. It sounds like you've done a lot with Asterisk.... didn't you hit brick walls every time you tried to do anything remotely complex with it?

Douglas.


-----Original Message-----
From: Freddi Hansen [mailto:fh at danovation.dk]
Sent: Tuesday, February 14, 2006 4:36 PM
To: asterisk-users at lists.digium.com
Subject: re:[Asterisk-Users] Multiple AGI Issues


>
>
>
>
> To:
> "Asterisk Users Mailing List - Non-Commercial Discussion" 
> <asterisk-users at lists.digium.com>
>
>
> I've got several issues with AGI/FastAGI
>
> 1. When an AGI script sends a command to Asterisk via stdin, why does Asterisk block and not return a result until the command is complete? Specifically, the dial command. If I send a Dial command to Asterisk, I don't get a return result until AFTER the call is HUNG UP. Not when it's ringing, not when the call is connected, but when it's DISCONNECTED. Why is that? How are you supposed to use commands like CHANNEL STATUS if you have to wait until the call is hung up, to check it's status?
>
> 2. Why do AGI scripts stay in memory until a call is complete? Is there any way to have the script terminate when a call is connected? With this scenario, you have a script for every single call in place, and that's really bad from a system resource perspective.
>
> 3. Seems that no scripting language is up to the task of FastAGI. Perl's threads aren't thread-safe with DBI and Python's aren't completely thread safe either. Don't know about Ruby, and I ain't no C programmer. What have people implemented? I also don't like the threading approach, because if something goes wrong with the script/server, you lose the ability to place ANY calls.
>
> Doug
>
>   
Hi,
If you want to have a speedy system that doesn't steal to many system 
resources then you have to use FastAGI. That being said you have to 
program your FastAGI server so it's completely event driven. The way to 
deal with f.ex. the dial command can be to let the FastAGI set a 
dialplan variable and then send the control back to the dialplan which 
then can execute the dial command that your FastAGI did prepare. I 
prefer to use perl for most AGI/FastAGI solutions, the servers are 
started out of inittab so no forking overhead during call handling. I do 
normally build FastAGI servers around 'select' so the process is either 
working or waiting on requests. I know you will say that means that no 
FastAGI request are served while I wait for database responses. The 
workaround is to start more than one copy of your FastAGI server on 
different ports. Create a global variable in your dialplan ,  increment  
on each call  - do a mod(4)  if you have  4 servers  so you can 
interleave the FastAGI requests between the servers.  If you need 
persistent data for you 'after call' process then use you DB system.
Let your FastAGI server write a dialplan status variable so you can 
retry another FastAGI server in case first one fails.
It's not difficult to get 100+ call setups per second with this approach.
b.r.
Freddi

   

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