Now we're consuming this API with http_client (synchronously) and as there's no way to speed up the API (pipeline executions, delays on external api's etc etc) we're hitting a limit where all children become busy waiting for the API to answer.

So i decided to move to http_async_client and started working on it on the lab with this first and base concept to test.

request_route {


#for testing purposes only
if(is_method("ACK")){
exit;
}
    $http_req(all) = $null;
    $http_req(suspend) = 1;
    $http_req(timeout) = 500;
    $http_req(method) = "POST";
    $http_req(hdr) = "Content-Type: application/json";
    jansson_set("string", "event", "sip-routing", "$var(cre_query)");
    xlog("L_INFO","API ASYNC ROUTING REQUEST: $var(cre_query)\n");
    $http_req(body) = $var(cre_query);
    t_newtran();
    http_async_query("http://192.168.86.128:8000/", "CRE_RESPONSE");
}

http://192.168.86.128:8000/ receives the POST, randomly creates a delay between 0.5 and 1 second and responds (simulating the real api with an excess delay to probe the concept)

Then

route[CRE_RESPONSE] {
    if ($http_ok && $http_rs == 200) {
        xlog("L_INFO","CRE RESPONSE: $http_rb\n");
# for testing purpose, Contact content will be replaced from the received api response
append_to_reply("Contact: <sip:1234@google.com>\r\n");
    send_reply(302,"Moved Temporarily");
exit;
    }
    send_reply(500, "Internal error");
    exit;
}

INVITE is received and processed, API is called, after API response, 302 is replied and then an ACK (ignored by now).

Situation is that the 302 retransmitted

   37 1519.846253067 192.168.86.34 → 192.168.86.128 SIP/SDP 585 Request: INVITE sip:service@192.168.86.128:5060 |
   38 1519.848100380 192.168.86.128 → 192.168.86.34 SIP 318 Status: 100 Trying |
   39 1520.094997642 192.168.86.128 → 192.168.86.34 SIP 407 Status: 302 Moved Temporarily |
   40 1520.102323728 192.168.86.34 → 192.168.86.128 SIP 453 Request: ACK sip:service@192.168.86.128:5060 |
   41 1520.591300933 192.168.86.128 → 192.168.86.34 SIP 407 Status: 302 Moved Temporarily |
   42 1521.591061065 192.168.86.128 → 192.168.86.34 SIP 407 Status: 302 Moved Temporarily |
   43 1523.591227956 192.168.86.128 → 192.168.86.34 SIP 407 Status: 302 Moved Temporarily |

18(24) DEBUG: tm [t_reply.c:1703]: t_retransmit_reply(): reply retransmitted. buf=0x7f6d79745dc0: SIP/2.0 3..., shmem=0x7f6d75187fd8: SIP/2.0 3
18(24) DEBUG: tm [t_reply.c:1703]: t_retransmit_reply(): reply retransmitted. buf=0x7f6d79745dc0: SIP/2.0 3..., shmem=0x7f6d75187fd8: SIP/2.0 3
18(24) DEBUG: tm [t_reply.c:1703]: t_retransmit_reply(): reply retransmitted. buf=0x7f6d79745dc0: SIP/2.0 3..., shmem=0x7f6d75187fd8: SIP/2.0 3
18(24) DEBUG: tm [timer.c:634]: wait_handler(): finished transaction: 0x7f6d75184cc8 (p:0x7f6d74f600c8/n:0x7f6d74f600c8)
18(24) DEBUG: tm [h_table.c:132]: free_cell_helper(): freeing transaction 0x7f6d75184cc8 from timer.c:643

Any help to avoid the retransmission and make the transaction just finish right after the 302 will be appreciated.

regards