We have a FO setup with hostname, and we aren't able to access the low code app from certain servers, using the defined hostname. On the servers where it doesn't work, performing a nslookup to the hostname, the first address that is returned is from the offline/backup agent:
On the servers where it works, performing a nslookup, the online agent is listed first, and I'm able to connect to the low code app.
What can I do to resolve this constraint?
Not sure if you are facing the same issue as we had, but we had issues in the past with the URL rewrite rules in IIS.
Normally when DM is offline it should rewrite all traffic to the other agent (except for the EndPoints.txt and ConnectionSettings.txt). This is configured in IIS under the 'Default Web Site' => 'URL Rewrite' (under Features view). There you should see the 'dataminer-failover-reverseproxy-rule' which should be enabled on the FO agent and Disabled on the main agent. If the rule is not enabled on the FO, then it might not correctly point to the main once the nslookup resolves to the FO address.
Maybe have a look if these rules are correctly set?