[sr-dev] Distinguish between local 408 generated after "fr_inv_timer" and "fr_timer"

[Andrei Pelinescu-Onciul]

On Mar 25, 2010 at 13:44, I??aki Baz Castillo <ibc at aliax.net> wrote:
> Hi, this is a common issue reported by other users. Imagine I do
> failover between two gateways based on request timeout:
> 
> ------------------------------
> failure_route[FAILURE_ROUTE_OUT] {
> 
>   # Locally generated 408 due to transaction timeout:
>   if (t_local_replied("last") && $T_reply_code==408) {
>     xlog("L_ERROR", "_ERROR_ $T_reply_code local replied => failover\n");
>     ... do failover ...
>   }
> 
> }
> ------------------------------
> 
> 
> The above code runs when the gateway-1 doesn't reply at all so
> "fr_timer" expires (let's say 5 seconds).
> 
> The problem is that such code also runs when no final response at all
> is received from gateway-1 in "fr_inv_timer" (let's say 150 seconds).
> This is, 408 is locallly generated even if the proxy has received
> provisional responses for such transaction.

Try t_any_replied()
(http://sip-router.org/docbook/sip-router/branch/master/modules/tm/tm.html#t_any_replied)

E.g.: 
 if (t_check_status("408"){
    if (!t_any_replied()) {
        t_reply(503, "Try again later, busy gws");
        exit;
    }
 }

> 
> Main problem this originates is the fact that the list of gateways
> could end without any of them giving a final reply, and when no more
> gateways are available it's common to reply 500/503 to the client.
> 
> Two workarounds:
> 
> a) When no more gateways are available inspect if $T_reply_code==408
> and then reply 408 rather than 500/503.
> I don't like it as if no one gateways has replied a provisional
> response in "fr_timer" then I have a *real* problem and I should reply
> 500/503.
> 
> b) Enable a flag(PROVISIONAL_RECEIVED) when a provisional response is
> received and then reply 408/480 when no more gateways are available.
> 
> 
> Anyhow, there should be (IMHO) a in-built way to determine if the 408
> occurs after "fr_timer" or "fr_inv_timer". Do I miss something? do you
> consider this a real need?

I don't consider this a real need, however it already can be done easily :-)

Andrei