[sr-dev] [tracker] Task opened: Dispatcher Round Robin Logic not Working with Dispatcher Table with FQDNs

[sip-router]

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A new Flyspray task has been opened.  Details are below. 

User who did this - Ed James (erj01) 

Attached to Project - sip-router
Summary - Dispatcher Round Robin Logic not Working with Dispatcher Table with FQDNs
Task Type - Bug Report
Category - Core
Status - Unconfirmed
Assigned To - 
Operating System - Linux
Severity - High
Priority - Normal
Reported Version - 4.0
Due in Version - Undecided
Due Date - Undecided
Details - I'm using the dispatcher module (Linux Kamailio v4.0 server) to load balance between two media servers and have two records in the dispatcher table as follows:

id, setid, destination, flags, priority, description
50, 40, sip:192.168.2.111:5066;transport=tcp, 0, 0, SomeDescription
51, 40, sip:10.1.0.119:5060, 0, 0, SomeDescription

If I call ds_select_dst("40", "4") then it works perfectly and calls are sent alternately to 10.1.0.119 and 192.168.2.111 - that's all OK.

The issue arises when I use the FQDNs for these two machines in the dispatcher records so I've got:

id, setid, destination, flags, priority, description
50, 41, sip:LYNCMESLOADBAL1.RedwoodLync.com:5066;transport=tcp, 0, 0, SomeDescription
51, 41, sip:LYNCMESLOADBAL2.RedwoodLync.com:5060, 0, 0, SomeDescription

I've then got Host(A) records on the DNS server (192.168.2.1) as follows:
LYNCMESLOADBAL1.RedwoodLync.com --> 192.168.2.111
LYNCMESLOADBAL2.RedwoodLync.com --> 10.1.0.119

On the Linux box System-->Admin-->Network-->Network Configuration-->DNS I've got Primary DNS as 192.168.2.1. If I do nslookup on either of the FQDNs they work fine do I think the DNS is working.

If I call ds_select_dst("41", "4") then it sends the first call to 10.1.0.119 and then all subsequent calls to 192.168.2.111 and doesn't round robin between the two records.

So the issue is that the round robin doesn't seem to work when the dispatcher table contains FQDNs for machines for which DNS lookup does work and for which round robin does work with ip addresses.

I've tried the following to switch off any dns caching but still have the issue:
use_dns_cache=off
dns_cache_init=off 
  
Anyone seen this before or have any suggestions ?

Thanks in advance for your help - much appreciated.

More information can be found at the following URL:
http://sip-router.org/tracker/index.php?do=details&task_id=459

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