> On Dec 23, 2024, at 10:56 am, Ben Kaufman via sr-users
> <[email protected]> wrote:
>
> This came off a bit more harsh than I intended. I think I understand the
> advantage of EVAPI in that it can initiate a command to Kamailio (thus
> Kamailio doesn't need to hold the thread, possibly it doesn't need to store
> the message even), but it would still be nice to have a higher level overview
> of how this would be achieved. Not even example code, but more a base
> architecture explanation / diagram of the flow.
It's probably not complicated enough to warrant a diagram.
1) EVAPI server is initialised:
loadmodule "evapi"
modparam("evapi", "workers", 3)
modparam("evapi", "bind_addr", "xxx:10399")
2) TCP client connects to this socket when it becomes available;
2) Kamailio receives request and serialises it (e.g. JSON), embedding the
transaction ID and label in whatever serialisation structure is used, then
emits it on the EVAPI bus, e.g.
evapi_async_relay("invite_request:$T(id_index):$T(id_label):$(var(data){s.encode.base64})");
3) TCP client reads this package off the wire; the built-in netstring support
is ideal. It then processes it, generates a response, serialises it, and puts
it back on the wire. Vitally, the $T(id_index) and $T(id_label) are embedded in
the response, allowing Kamailio to resume the transaction:
4) Kamailio receives this message in $evapi(msg), in this event_route, and
resumes the transaction into route[RESUME]:
event_route[evapi:message-received] {
...
jansson_get("tm_trans.tm_index", "$evapi(msg)", "$var(t_index)");
jansson_get("tm_trans.tm_label", "$evapi(msg)", "$var(t_label)");
t_continue("$var(t_index)", "$var(t_label)", "RESUME");
...
}
5) In route[RESUME], INVITE processing continues as normal, enlightened by
anything else that was deserialised out of $evapi(msg).
EVAPI is my favourite Kamailio module, and the only way I interface with
outside services, when it's up to me.
-- Alex
--
Alex Balashov
Principal Consultant
Evariste Systems LLC
Web: https://evaristesys.com
Tel: +1-706-510-6800
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