4 Feb
2014
4 Feb
'14
1:12 p.m.
P.S. There is a dispatcher-oriented example config in the package that
can help get you started:
http://git.sip-router.org/cgi-bin/gitweb.cgi?p=kamailio;a=blob;f=modules/di…
But the central idea is really quite simple:
1. Load the 'dispatcher' module:
loadmodule "dispatcher"
2. Configure 'dispatcher' to load a list of hosts, either from a
database (db_url), or else from a flat text file:
modparam("dispatcher", "db_url",
"DB_DRIVER://DB_USER:DB_PASSWORD@DB_HOST/DB_NAME")
modparam("dispatcher", "table_name", "dispatcher")
modparam("dispatcher", "force_dst", 1)
modparam("dispatcher", "flags", 2)
modparam("dispatcher", "dst_avp", "$avp(s:d_dst_set)")
modparam("dispatcher", "grp_avp", "$avp(s:d_grp_set)")
modparam("dispatcher", "cnt_avp", "$avp(s:d_cnt_avp)")
modparam("dispatcher", "ds_probing_mode", 0)
3. In your initial request route, pick a host from the dispatcher set,
based on the round-robin strategy (algorithm #4):
if(!ds_select_domain("1", "4")) {
# This should only happen if the route set is empty.
sl_send_reply("503", "Out of Gateways");
xlog("L_ERR", "[R-DISPATCHER-INITIAL:$ci] !> "
"No gateways available!\n");
exit;
}
xlog("L_INFO", "[R-DISPATCHER-INITIAL:$ci] -> "
"Selected gateway: $rd:$rp\n");
t_on_failure("DISPATCHER_ROLLOVER");
4. If that gateway should fail to respond or to accept the call, catch
that event in a failure_route and pick the next gateway from the set:
failure_route[DISPATCHER_ROLLOVER] {
if(t_is_expired() || t_is_canceled())
exit;
if(!ds_next_domain()) {
# This should happen when we are out of gateways/have tried
# the last one in the route set.
xlog("L_ERR", "[R-DISPATCHER-ROLLOVER:$ci] !> "
"No more gateways in route set\n");
t_reply("503", "Out of gateways");
exit;
}
xlog("L_INFO", "[R-DISPATCHER-ROLLOVER:$ci] -> "
"Attempting relay to new gateway: $rd:$rp\n");
t_on_failure("DISPATCHER_ROLLOVER");
t_relay();
}
And repeat recursively until you run out of gateways.
5. The timeouts due to non-response of the gateway are regulated by the
transaction state module (TM):
modparam("tm", "fr_timer", 3000) # 3 seconds
modparam("tm", "fr_inv_timer", 90000) # 1.5 minutes.
You can read more about these values here:
http://kamailio.org/docs/modules/4.1.x/modules/tm.html#fr_timer
http://kamailio.org/docs/modules/4.1.x/modules/tm.html#fr_inv_timer
-- Alex
--
Alex Balashov - Principal
Evariste Systems LLC
235 E Ponce de Leon Ave
Suite 106
Decatur, GA 30030
United States
Tel: +1-678-954-0670
Web: http://www.evaristesys.com/, http://www.alexbalashov.com/