Access to XMLHttpRequest at 'https://events.launchdarkly.com/events/bulk/6374af9a71e138110cdb10cd' from origin 'https://localhost:5001' has been blocked by CORS policy: Request header field request-context is not allowed by Access-Control-Allow-Headers in preflight response.

[ptldanielthompson]

Access to XMLHttpRequest at 'https://events.launchdarkly.com/events/bulk/6374af9a71e138110cdb10cd' from origin 'https://localhost:5001' has been blocked by CORS policy: Request header field request-context is not allowed by Access-Control-Allow-Headers in preflight response.

[kinyoklion]

Hello @ptldanielthompson,

This is going to affect the analytics and other features in the UI of LaunchDarkly. Information like context attributes, or data for experimentation, are delivered through this mechanism.

It soulds like something is adding a "request-context" header to the event payloads. This isn't something that the LaunchDarkly SDK does, and isn't a header that our endpoints accept.

I am not familiar with ApplicationInsights, but if its usage involves an SDK, then it may be that it is modifying requests to incorporate this header (from some searching it seems like it may be related to a cross origin correlations feature). Things like this sometimes happen with various APM tools.

So, first I would see if the issue goes away if you don't use ApplicationInsights locally. If it does, then you can work from that to determine how to prevent ApplicationInsights from modifying LaunchDarkly requests.

Thank you,
Ryan