asterisk users - Jan 2010 - AGI perl script set timeout within script?

Hi All,

I'm running an AGI, calling a perl script the does number lookups to a
remote server.  I would like to put a timeout in the script.  The
problem I'm running into is if the DNS server is not responding, the
script hangs and waits for 30 seconds before returning to the Asterisk
dialplan.  I would like a timeout of 1 second, then return.

Here is my clean script:

***********************************************************
#!/usr/bin/perl
$|=1;
#####################    Modules to Use       ###############
use Asterisk::AGI;
$AGI = new Asterisk::AGI;
my %input = $AGI->ReadParse();
# Set variables according to supplied arguments
$number = $ARGV[0];
$AGI->exec("agi","agi://agi.server.com/script.agi?user=username&number=$number");
***********************************************************

Any assistance will be appreciated.

Thanks.

JR
-- 
JR Richardson
Engineering for the Masses

On Thu, 7 Jan 2010, JR Richardson wrote:
> I'm running an AGI, calling a perl script the does number lookups to a 
> remote server.  I would like to put a timeout in the script.  The 
> problem I'm running into is if the DNS server is not responding, the 
> script hangs and waits for 30 seconds before returning to the Asterisk 
> dialplan.  I would like a timeout of 1 second, then return.
I'm a C weenie, so I can't provide Perl code. But it should look
something
like this:

// handle the alarm
static	void				lookup_failed
 	(
 	  void
 	)
 	{
 	exit(EXIT_FAILURE);
 	}

int					main
 	(
 	)

 	...

// set a signal alarm handler
 	signal(SIGALRM, (void (*)(int))(int)lookup_failed);

// set the alarm to go off in 1 second
 	alarm(1);

// lookup my number
 	do_lookup(dnis);

// cancel the alarm
 	alarm(0);

 	...

Of course, solving the real issue (DNS lookups), or masking it with a 
local caching server or even a /etc/hosts file are viable alternatives.

-- 
Thanks in advance,
-------------------------------------------------------------------------
Steve Edwards       sedwards at sedwards.com      Voice: +1-760-468-3867 PST
Newline                                              Fax: +1-760-731-3000

On Thu, Jan 7, 2010 at 6:27 PM, JR Richardson <jmr.richardson at
gmail.com> wrote:
> problem I'm running into is if the DNS server is not responding, the
> script hangs and waits for 30 seconds before returning to the Asterisk
> dialplan. ?I would like a timeout of 1 second, then return.
A few things...

* stop using DNS? Problem solved.
* put nagios monitoring on your DNS server?
* put in a second DNS server, and tune your DNS timeout to a very low
value in /etc/resolv.conf (read the man page) before jumping to next
server?

Or you could use the Perl language feature, which is called 'alarm'.
Google around for some code samples.

None of these are actually specific to asterisk, as it turns out. I
don't know of any explicit asterisk method to force a timeout.

> >> On Thu, Jan 7, 2010 at 6:27 PM, JR Richardson
> <jmr.richardson at gmail.com>
> > wrote:
> >>> problem I'm running into is if the DNS server is not
responding, the
> >>> script hangs and waits for 30 seconds before returning to the
Asterisk
> >>> dialplan. ?I would like a timeout of 1 second, then return.
> >>
> > On Thursday 07 January 2010 18:59:24 David Backeberg wrote:
> >>
> >> * stop using DNS? Problem solved. * put nagios monitoring on your
DNS
> >> server? * put in a second DNS server, and tune your DNS timeout to
a
> >> very low value in /etc/resolv.conf (read the man page) before
jumping
> >> to next server?
> >>
> >> Or you could use the Perl language feature, which is called
'alarm'.
> >> Google around for some code samples.
> 
> On Thu, 7 Jan 2010, Tilghman Lesher wrote:
> 
> > Ah, but Perl isn't actually doing the DNS lookup.  If you examine
his
> > script, he's merely passing back a name to the Asterisk process,
which
> > is then calling inet_aton(), which is the reason why he cannot control
> > it from within the script.  What he'd actually need to do is to
start
> > using Net::DNS to do the resolution on that name, first, perhaps even
> > going as far as to connect to the server himself, and relay the
channel
> > between the AGI interface and the remote TCP interface.
> >
> > Then, he could use alarm() or the Time::Hires module to ensure his own
> > timeouts override the builtins.  But as it stands now, it's all
> > Asterisk.
> 
> If the DNS lookup is being done by Asterisk to resolve the FastAGI server
> name. If the DNS lookup is for the (assumed) database server in his script
> then the suggestions to use alarm() would do the trick.
> 
> I guess we need clarification from the OP.
I tend to agree with Tilghman on this. I tried the perl script eval, alarm,
$SIG{ALRM} functions till I was blue in the face from cussing at the screen.
It does not appear that the perl script is doing the DNS query, otherwise
the eval alarm would timeout and pass control back to asterisk.  Another
indication is that '#define MAX_AGI_CONNECT 2000' in res_agi is not
being
invoked because the timeout is around 30 seconds.  Is that 30 second timeout
built into Asterisk?  Can I put an absolute timeout on an agi script from
the dialplan prior to calling the agi application?  Maybe I'll fork a macro
with a timeout, yea, that's it, let start forking, something new to cuss at.

Thanks for your input guys.

JR

> What about:
>
> 1) Fixing the slow responding DNS server?
>
> 2) Tweaking /etc/resolv.conf options?
>
> 3) Setting up a caching name server on your Asterisk host?
>
> 4) Adding the AGI server host name and IP address to /etc/hosts?
>
> 5) Using the IP address of the AGI server in your dialplan?
>
Ok, I went with #4 for a bit, then resolved to #5 (pardon the pun), works fine.

Thanks.

JR
-- 
JR Richardson
Engineering for the Masses