Solarmon,

Yes, that code is your issue. While it makes sense to mark the remote 
destination unreachable on some error responses possibly, or certainly on lack 
of response, this code is marking the destination unreachable on receipt of any 
5xx or 6xx response (or timeout), without regard to whether the response came 
directly from that node or from further upstream. This does not seem desirable.

The code is also performing failover using the dispatcher for any of these 
codes, which also does not account for the possibility that the error came from 
further upstream and trying another dispatcher node may not be warranted or 
helpful.

If you have control over the nodes that are the dispatcher targets, what we 
have done is to add a customer header to any error replies sent directly from 
that node. This allows the receiving node to know that the issue was local to 
the remote node and not relayed from further upstream and that ds_mark_dst and 
ds_next_dst are appropriate. We also still check for timeout too, of course. 
But there are other ways to do this as well.

Ben Newlin

From: Users <[email protected]> on behalf of solarmon 
<[email protected]>
Reply-To: OpenSIPS users mailling list <[email protected]>
Date: Monday, June 8, 2020 at 6:57 AM
To: OpenSIPS users mailling list <[email protected]>
Subject: Re: [OpenSIPS-Users] 502 Bad Gateway events leads to calls being 
rejected with 480 Temporarily Unavailable

Hi Diptesh ,

Thanks for your reply.

Apologies, I'm using the term 'blacklist' to generally mean that the endpoints 
are not available.

Also, the 502 Bad Gateway is response to an INVITE, not SIP OPTIONS, returned 
by the far end and the ITSP is just passing that back to us, because the call 
has failed. For such call failures, I'm not expecting for the dispatcher 
endpoints to be marked as unavailable for routing.

I am not using, or have not set, the 'ds_define_blacklist (str)' option in my 
dispatcher module config.

My probing mode is:

modparam("dispatcher", "ds_probing_mode", 1)

I'm not seeing anything in the logs regarding the dispatcher nodes going into 
Probing mode - should there be logs for that, or can it be enabled to be logged?

When I check the endpoints with ' opensipsctl dispatcher dump' they always seem 
to be 'Active' - so it is either they are like that, or they may have only been 
in 'Probing' mode very briefly. Again, I was hoping to see mode/state change in 
the historical logs.

In my opensips.cfg (which was created for me) I can see the following code, 
which looks like this is where it is introducing this behaviour in question:

failure_route[call_failover]
{
        xlog("[$ci] call failed to established with $T_reply_code code\n");

        rtpproxy_unforce("$avp(rtpp_set)");

        if (t_was_cancelled()) {
                t_reply("487","Request cancelled");
                exit;
        }

        # any failure indication ?
        if ( t_check_status("[56][0-9][0-9]")
        || (t_check_status("408") && t_local_replied("all"))
        ) {
                xlog("[$ci] destination $rd failed  with $T_reply_code -> 
retry\n ");

                ds_mark_dst("p");

                if ( ds_next_domain() ) {
                        xlog("[$ci] using new destination <$rd>\n ");

                        # send it out again
                        t_on_failure("call_failover");
                        t_relay();
                        exit;
                } else {
                        xlog("[$ci] no other destination to retry\n ");
                        t_reply("503","Service not available");
                        exit;
                }
        }

        # if call failure, allow the reply to propagate to caller
        exit;
}


Thank you for the tip about the  'modparam("dispatcher", "options_reply_codes", 
"502")' option. I will try that if it is not recommend to change the above code.

Thank you.


On Mon, 8 Jun 2020 at 10:47, Diptesh Patel 
<[email protected]<mailto:[email protected]>> wrote:
Hello Solarmon,

Need some clarification on term blacklisting, Are you using the blacklist for 
Probing Mode of destination? or Are you using the 'ds_define_blacklist (str)' 
parameter. If you are not using the blacklist parameter then below information 
help you. It is great if you share your script snippet and output of 
'opensipsctl dispatcher dump' which shows you the current status of your 
destinations.

If you are getting success(200 OK) response on OPTIONS then it is not possible 
that you got a negative response from a destination and it will not be 
blacklisted(probing mode) in dispatcher until you blacklist(probing mode) from 
the script using 'ds_mark_dst()' exported function. I doubt that you are also 
getting '502 Bad Gateway' on OPTIONS which is sending to the destination to 
check the availability.  If It is right and you want to add the 502 response as 
a good response for OPTIONS. you can add the 502 as 'modparam("dispatcher", 
"options_reply_codes", "502")'.

Thanks & Regards
Diptesh Patel
Software Developer
Ecosmob Technologies Ltd,
Ahmedabad
Mo:+919898962659


On Mon, Jun 8, 2020 at 2:24 PM solarmon 
<[email protected]<mailto:[email protected]>> wrote:
Hi,

I'm trying to understand whether this is the correct or expected behaviour.

We have two destinations configured in Dispatcher.

What I am noticing is that when we receive 502 Bad Gateway messages (logged as 
("call failed to established with 502 code") from both endpoints. After both 
endpoints have returned 502 Bad Gateway, opensips pass back 503 Service 
Unavailable back to the originating endpoint of the call. However, subsequent 
calls are being immediately rejected with 480 Temporarily Unavailable (logged 
as "failed to find an available destination, rejecting") for a period of time.

It seems that opensips is blacklisting the Dispatcher endpoints because of 
receiving the 502 Bad Gateway messages. Is this the correct/expected behaviour? 
I would have thought the blacklisting should be based on the SIP OPTIONS sent 
to the Dispatcher endpoints.

I do not currently see any issues with SIP OPTIONS to these endpoints so I'm 
confused as to why they are seemingly blacklisted.

If this is the correct/expected behaviour, can it be changed to only blacklist 
based on the SIP OPTIONs pings?

Thank you.
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