Access-Control-Allow-Headers Error in EUM

[pclark]

Symptoms

You encounter an issue with the POST to /eumcollector/beacons.

JS error is "Request header field X-TS-AJAX-Request is not allowed by Access-Control-Allow-Headers".

Diagnosis

Research revealed that Access-Control-Allow-Headers is a CORS property.

1. For this scenario, there were two app environments: APP1 and APP2.
2. EUM data was being seen in APP1 but not in APP2.
3. Verified that the adrum.js and adrum-ext.[ver].js match except for app key.
4. Both apps were hitting the same load balancer, F5.
5. Only APP2 has SSO enabled via WebSphere + Active Directory.

Solution

Turns out that this was an F5 configuration error, even though "everything's the same for both environments" with regard to F5.

Customer was running the Application Security Manager module on F5. It's supposed to be transparent, not do anything. The F5 team disabled the ASM view on APP2 because it was disabled on APP1. This fixed the CORS problem affecting the call to /eumcollector/beacons.