Per-endpoint instrumentation doesn't show up with overlapping API endpoints.

[unr-srs]

Using lts-14.27.

The API type has overlapping endpoints plus a raw endpoint for Pandoc-generated API documentation. The application runs hoisted on a custom monad

type TheAPI = "try" :> "this" :> ...
                  :<|> "try" :> "that" :> ... 
                  :<|> "try" :> "those" :> ...
                  :<|> "lookup"
                  :<|> Raw

theAPI :: Proxy TheAPI
theAPI = Proxy

apiServer :: ServerT TheAPI CustomM
apiServer = ... :<|> ... etc

myApp config = serve theAPI $ hoistServer theAPI (nt cconfig) apiServer

where nt does the natural transformation via runReaderT and runLoggerT.

After a vanilla System.Remote.Monitoring.forkServer, I'm wrapping the application as follows

wrapWithEkg <- newStore >>= monitorEndpoints theAPI
runSettings settings (wrapWithEkg $ myApp cfg)

where runSettings does runTLS over a custom TCP port.

I can connect to EKG. The standard EKG metrics are there, but none of the Servant specific measurements show up.

[fiadliel]

I've been using similar code to this in another project, and found that more complex routes also didn't show up. There is some code that I don't understand, and removing a check made reporting work better (thought it hasn't been tested for long, where "long" is more than a few requests on my laptop).

The code in question is:

instance ReflectMethod method => HasEndpoint (Verb method status cts a) where
    getEndpoint _ req = case pathInfo req of
        [] | requestMethod req == method -> Just (APIEndpoint [] method)
        _                                -> Nothing
      where method = reflectMethod (Proxy :: Proxy method)

(and similar instances).

The pathInfo check doesn't make sense to me, and I suspect it should be removed; the path alignment is already checked by captures and static path components. Also, the enumerateEndpoints function doesn't include the check in question.

This was an error.

[fiadliel]

Sorry for the above; a few more hours show that I was wrong (the check proves that there aren't further segments in the path).

I've tried to reproduce at least whether TheAPI returns a value to getEndpoint. Would you be able to try locally, and see if it returns a correct value?

e.g. in the repl:

> :set -XTypeOperators -XDataKinds
> :{
>   type TheAPI = "try" :> "this" :> GetNoContent
>                     :<|> "try" :> "that" :> GetNoContent
>                     :<|> "try" :> "those" :> GetNoContent
>                     :<|> "lookup" :> GetNoContent
>                     :<|> Raw
> :}
> import Servant.Ekg
> import Data.Text
*Servant.Ekg Data.Text> getEndpoint (Proxy :: Proxy TheAPI) (defaultRequest{pathInfo = pack <$> ["try", "that"]})
Just (APIEndpoint {pathSegments = ["try","that"], method = "GET"})

All the tests I've tried here with the above API return the correct result, but I wonder if there's something different about your API.