Hello Everyone, I have a question regarding MDC and Ktor. We are currently using the `CallLogging` p...

# server

[Sanjay Kasi]

Hello Everyone, I have a question regarding MDC and Ktor.
We are currently using the CallLogging plugin to inject MDC values in the pipeline like so:

fun Application.module() {
  install(CallLogging) {
		mdc("clientIpAddress") { call ->
      call.request.header("X-Forwarded-For") ?: "UNDEFINED"
    }
  }
}

We are generating a userId within the route which needs to be added to MDC such that it is available outside the current co-routine context:

fun Application.myRoutes() {
  routing {
    get("/testMDC") {
	 	MDC.putClosable("userId", "${UUID.randomUUID()}") // <-- This is thread local and does not carry onto other co-routines
    }
  }
}

The clientIpAddress works fine and is logged throughout but userId only logs in local context. Is there any work around for this?

[Sam]

Is MDC from Slf4J? You could take a look at https://github.com/Kotlin/kotlinx.coroutines/blob/master/integration/kotlinx-coroutines-slf4j

[Sam]

Not sure if it will solve this exact problem, but it might provide a workable alternative

[Sanjay Kasi]

Is MDC from Slf4J?

Correct. Will check it out and revert. Thanks!

[Pat Kujawa]

We've had to use, e.g. Dispatcher.IO + MDCContext() from that slf4j coroutine lib in every new coroutine context to ensure MDC flows through all coroutines.