4 Feb
2006
4 Feb
'06
5:15 p.m.
Greg,
this is the happy case where parallel forking is involved. The serial
forking works by keeping in AVPs the next uris to be tried (in case of
negative replies). But the AVPs are per transaction and you cannot say
on which specific branch to be used (in case of parallel forking).
Also, from performance reasons, the best approach will be to try to
perform the sequential queries only if the previous tried failed...
I will try to put tougher a plan about how to have failover in the resolver.
regards and nice weekend to you also,
bogdan
Greg Fausak wrote:
Bogdan,
Thanks for the reply.
Will this work:
here are some examples of how to uses this new functionality:
1) enum doing serial forking:
{
.....
enum_query("e164.arpa.","voice");
serialize_branches(1);
if (!next_branches()) {
sl_send_reply(...no enum found...);
exit;
}
t_on_failure("1");
t_relay();
}
failure_route[1] {
if (next_branches()) {
t_relay();
}
}
I haven't tried it yet. But I think it is an example
of serial forking using naptrs.
Have a great weekend!
---greg
On Feb 4, 2006, at 4:01 AM, Bogdan-Andrei Iancu wrote:
Hi Greg,
at the moment there is no retry support for neither NAPTR nor SRV.
The resolver loops through all NAPTR/SRV records and looks for the
first NAPTR|SRV|A pair of records that can be successfully resolved
to IP address.
The biggest problem with having retry support for the resolve is the
combination between parallel and serial forking. Lets supposed the
following scenario:
uriA parallel forks to uriX and uriY
both uriX and uriY leads to distinctive sets of NAPTR/SRV records.
in such a case, even if it's a single transaction, you have to keep
the state of the resolver for each branch to be able to do serial
forking independently on each of them.
Another problem is detecting the failures. According to "4.3 Details
of RFC 2782 Process" specifies usage on ICMP for UDP failures...and
ICMP support is not reliable (depends on OS) and tricky to implement.
Do not get me wrong, I am not saying it's impossible, but it will
take some time to get to it... :)
regards,
Bogdan
Greg Fausak wrote:
Bogdan,
This is great news! Thank you! I've got
a questions about retries.
I'm curious if retries are built in, or do I employ t_on_failure?
What I mean is...
How do I get the t_relay() to try subsequent naptrs and/or srvs in the
event the current one fails? Is all of that automatic, or do I need
a t_on_failure?
I think I understand that you skip ones that don't resolve, but,
what if
they resolve but the transaction times out either on the naptr or
on the srv?
Best,
-g
--
Greg Fausak
greg(a)thursday.com