Unrecognized requests in the Horizon Console XML API log

The Horizon Console dashboard shows a warning about unrecognized requests on the XML API protocol connection. These warnings normally have no direct effect on user sessions.

A typical log entry on the Horizon Connection Server looks like this:
[ConnectionServerHandler] Incrementing the warning count : Reason : unrecognized request detected

Worth knowing

• On Horizon 2209 and 2212 these warnings are usually false positives.
• From 2303 onwards they are worth looking into, to keep the user experience consistent.

If session problems such as dropped connections do occur on older versions like 2209 or 2212, it is often a problem with the load balancer persistence settings. Requests then get sent to the wrong connection server.

Cause

These warnings appear when a user tries to connect to the connection server with an expired session cookie.

Solution

1. The Horizon feature “View Unrecognized Session Count”
   Introduced in Horizon 2209, it shows harmless warnings on the dashboard. It lets administrators investigate dropped connections caused by unrecognized requests.
2. Improvements in Horizon 2303 and later
   From Horizon 2303 the error handling was extended. A typical log entry reads:
   [EventLogger] Error_Event:[BROKER_DETECTED_UNRECOGNIZED_SESSIONS] "ConnectionServer MyBroker detected 2 unrecognized requests for XMLApi protocol connection

That means network traffic is not reaching the connection server it should.

1. Investigating the load balancer
   • Disable the load balancer temporarily to identify where the problem comes from.
   • For the recommended persistence settings, see Monitoring health of Horizon Connection Server using Load Balancer, timeout, Load Balancer persistence settings in Horizon 7.x and 8 (56636).
   • Working with the load balancer vendor is worthwhile too.
2. The client IP address changing
   If the Horizon Client’s incoming IP address changes during an authenticated session, that may be logged as an unrecognized request.

Conclusion

These warnings are often harmless, but if sessions drop repeatedly or behave unexpectedly, check the network traffic and the load balancer configuration. Horizon 2303 brings additional tooling for finding and fixing the cause.