[SR-Users] DMQ problems

[Charles Chance]

Hi Aleksandar,


On 1 July 2018 at 07:08, Aleksandar Sosic <alex.sosic at evosip.cloud> wrote:

> Hi everyone,
>
> so adding some xlogs We've managed to find out what's happening.
> The request route was using:
> ```
>   if(is_method("KDMQ")){
> ```
> but this if was never triggered(!?)
> We changed that to
> ```
>   if($rm == "KDMQ"){
> ```
> And now it's working.
>
> So why is that? In the documentation there's an example with is_method:
> https://kamailio.org/docs/modules/5.2.x/modules/dmq.
> html#dmq.f.dmq_handle_message
> and I can recall it working a month ago.
>
>
Either way should work - there should be no difference between them. We are
using is_method everywhere and it works just fine.

Everything is working except for this message:
> ```25(42) ERROR: dmq [notification_peer.c:596]:
> notification_resp_callback_f(): deleting server sip:127.0.0.1:5060
> because of failed request```
> And that's because of the notification address on the kamailio node we
> use as DMQ server
>
>
I suspect setting localhost as the notification address is causing you some
problems - it's certainly not supported and although I've not tested it, it
wouldn't surprise me if this has something to do with your earlier issue.

You do not, in fact, need to maintain a dedicated node who's only role is
"DMQ server" as you have described it. I would recommend removing it
completely and allowing your other nodes to discover/communicate between
themselves.


> This portion of DMQ documentation says that `Default value is "NULL".`
> for the notification_address:
> https://kamailio.org/docs/modules/5.2.x/modules/dmq.
> html#dmq.p.notification_address
> But with NULL or NOT specifying a value kamailio does not start.
> Am I misunderstanding the documentation? Could this be a feature
> request or it's a bug?
>

Omitting the notification address should not cause an issue - what error do
you see in your log when it fails to start? If you get rid of the "DMQ
server' node as suggested above, though, this should be a none-issue.


> In a situation like our where kamailio nodes start and stop on demand
> without any prior defined topology or IP addresses defined it's hard
> to use DMQ module like that. That's why we introduced a DMQ server
> with a fixed IP address that it's handling only those packets (but
> it's a workaround).
>
> So my next question is:
> Do you guys have an idea on how could we handle DMQ on a very
> mutational infrastructure?


> Example: I have 2 kamailio nodes in the begining (no fixed IPs - using
> DHCP), then when there's demand the infrastructure starts another 2
> nodes, now I have 4 of them, then 3, one of the nodes randomly is
> stopped.
> And I want to use DMQ on these node to propagate information without
> using a DB. How could we do that?
>

Use multi_notify -
https://www.kamailio.org/docs/modules/stable/modules/dmq.html#dmq.p.multi_notify

If nodes are being added/removed dynamically then you'll probably also want
to employ some kind of service discovery mechanism, e.g. consul.


> Also another thing that we noticed is that the last node to be added
> is the one with no prior information regarding usrloc for example, it
> has only the changes happening from when it starts on. Could there be
> a method or modparam flag to force dmq sync of all the information
> upon the startup of another node (another possible feature request)?
>
>
See sync parameter -
https://www.kamailio.org/docs/modules/stable/modules/dmq_usrloc.html#usrloc_dmq.p.sync

Cheers,

Charles

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