[kamailio/kamailio] nats module subscriber issue when connected to more "nats_urls" (Issue #2916)
### Description, Troubleshooting, Reproduction
I have 3 go nats servers running and the following kamailio config for nats: ``` modparam("nats", "nats_url", "nats://127.0.0.1:4222") modparam("nats", "nats_url", "nats://127.0.0.2:4222") modparam("nats", "nats_url", "nats://127.0.0.3:4222")
modparam("nats", "subject_queue_group", "foo:2020") ...
event_route[nats:foo] { xlog("L_ERR", "==============> received $natsData"); } ``` I try to publish using some nats publisher (e.g. nats.c example/libuv-pub.c), and nothing gets printed in event route: ``` ./pub -s nats://127.0.0.1:4222 -txt "aaaaaaaaaaaa" -count 1 // event route log NOT printed ./pub -s nats://127.0.0.2:4222 -txt "aaaaaaaaaaaa" -count 1 // event route log NOT printed ```
However, if I try to publish on the last server "127.0.0.3", log *is* printed: ``` ./pub -s nats://127.0.0.3:4222 -txt "aaaaaaaaaaaa" -count 1 // event route log IS printed ```
I expected to see 1 log message for each of the above publish(es). Found this while implementing and testing #2915
Thanks, Stefan
Found in nats.h file, from nats.c git repo: ``` * By default, #natsConnection_Connect() attempts to connect to a server * specified in provided list of servers. If it cannot connect and the list has been * fully tried, the function returns an error. ``` So the lib behavior is to connect to **a single server** from the list, not to all servers in the list.
Closing this, as it is expected lib behavior. Will document this in "nats_url" modparam.
Thanks, Stefan
Closed #2916.
This sounds like a nice improvement, I submitted a PR to move the connection handling into a new struct. We can extend it into a linked-list by doing something like this: 
I think we should leave the default behavior of relying on libnats to do connection failover based on the server list it is given, and define a "name" on the connection to create simultaneous connections. perhaps using something similar to htable like ``` modparam("nats", "nats_url", "nats://127.0.0.1:4222;name=connection1") modparam("nats", "nats_url", "nats://127.0.0.1:5222;name=connection1") modparam("nats", "nats_url", "nats://127.0.0.1:6222;name=connection2") ```
This would create two sets of connections. "connection1" would contain server list of `nats://127.0.0.1:4222` and `nats://127.0.0.1:5222` "connection2" would contain server list of `nats://127.0.0.1:6222` We could then reference the connections by name in other modparams or functions.
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Emmanuel Schmidbauer -
Stefan Mititelu