[SR-Users] SIP Trunks

[Klaus Darilion]

On 14.10.2013 14:57, Keith wrote:
> Hi,
>
> Klaus, thank you for pointing me in the right direction with SIP trunks,
> got it working so thanks! Basically I did exactly what you said:
>
> - Dialled number
> - Match that number to a registered user (had to create a new table for
> that)
> - Lookup user
> - Replace dialled s@ with original number dialled
>
> Works like a charm, however, I have a question over speed and
> performance. As this is a SQL query and not held in memory is this SQL
> lookup doing to cause me problems? It's not a big query at the moment,
> but it could get quite big as I will need to map each number to a
> registered trunk.

It depends on your database. If the database is fast, this is usually 
not a problem. Many Kamailio users e.g. use the usrloc module without 
caching, thus every lookup() call requires a DB lookup. Also 
authentication is usually not cached, and requires a DB lookup for every 
SIP request (INVITE, REGISTER).

Thus, if the DB is fast, you are fine.

If the DB is slow or unreliable, then Kamailio is slow too. But usually 
you anyway need the DB for accounting and authentication - thus if the 
DB is not available quite often you do not want any calls to proceed (as 
you can not bill them).

Anyway, if you are afraid of DB performance, or you have quite slow 
queries which usually return the same result, you can use caching using 
the htable module. See the readme. But a simple example (untested): e.g. 
you want to cache the DID-to-user mapping for 1 hour.

modparam("htable", "htable", "dids=>size=10;autoexpire=3600;")

route {

   ....
   # incoming did is in $rU
   # use the DID as hash key
   $var(mapping) = $sht(a=>$rU);
   if ( $var(mapping) ) {
     xlog("Using cached mapping: $rU -> $var(mapping)");
     $rU = $var(mapping);
   } else {
     # your code to load the mapping from DB into $var(mapping)
     .....
     xlog("Loaded mapping from DB: $rU -> $var(mapping)");
     $rU = $var(mapping);
     # put the mapping into the hash table
     $sht(a=>$rU) = $var(mapping);
   }
   lookup(...);



regards
Klaus