Do not log certain 404s as "Unknown route"

When an endpoint returns 404, the transaction name in APM is logged as “<METHOD> Unknown route”. In some cases this is desired behavior, however it doesn’t really play well with REST. If, for example, the endpoint /api/customers/{id} returns 404 because the route exists but the customer with that id doesn’t, then we’d like to see this logged under endpoint name in APM instead of “Unknown route”.

Is your feature request related to a problem? Please describe. I guess this is related to: https://github.com/elastic/apm-agent-dotnet/pull/953/files

Describe the solution you’d like We’d like to be able to mark some endpoints in any way, so that their 404 response logs with correct transaction name

[gregkalapos]

I think we can adjust this. This part of the spec says how it should work:

This would normally also apply to requests to unknown endpoints, e.g. the transaction for the request GET /this/path/does/not/exist would be named GET unknown route, whereas the transaction for the request GET /users/123 would still be named GET /users/{id} even if the id 123 did not match any known user and the request resulted in a 404.

So based on this, the agent isn’t aligned with the spec. By looking a bit into this, I think this check here needs to be refined. If it matches a route, we should still take it as a transaction name, even if it returns 404.

@skuc-fp just in case you don’t know - you’ll still have the full url, it’s just not in the transaction name, so you can figure out which ids returned 404, but indeed you need to dig into every single transaction (see screenshot:)

We’ll discuss this, but to me it seems in the specific case with existing routes we should adapt the agent and always report those with the route as the transaction name.

[gregkalapos]

I opened https://github.com/elastic/apm-agent-dotnet/pull/1715 which addresses this issue.