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kotlinkotlin-coroutinesmdc

Kotlin coroutines MDCContext isn't restored

Just playing around with coroutines and logging MDC. I have a dummy example

@GetMapping("/dummy/{delay}")
suspend fun dummyEndpoint(@PathVariable delay: Int): ResponseEntity<String> {
    logger.debug("Outside the context. Start")
    withContext(MDCContext(mapOf("myKey" to "myVal"))) {
        logger.debug("Inside the context. Before the call")
        val response = WebClient.create()
            .get()
            .uri("http://postman-echo.com/delay/${delay}")
            .retrieve()
            .awaitBody<String>()
        logger.debug("Inside the context. After the call")
    }
    logger.debug("Outside the context. End")
    return ResponseEntity.ok("OK")
}

It produces next log message:

2020-07-30 19:42:09,817 - [DEBUG] - [reactor-http-nio-3] - [{}] Outside the context. Start
2020-07-30 19:42:09,836 - [DEBUG] - [reactor-http-nio-3] - [{myKey=myVal}] Inside the context. Before the call
2020-07-30 19:42:15,411 - [DEBUG] - [reactor-http-nio-4] - [{myKey=myVal}] Inside the context. After the call
2020-07-30 19:42:15,412 - [DEBUG] - [reactor-http-nio-4] - [{myKey=myVal}] Outside the context. End

My expectation was that the context will be cleared after withContext() block will be finished.

Inspired by https://medium.com/@elizarov/phantom-of-the-coroutine-afc63b03a131

This is more verbose, but it also avoids the need to restore the context after the call to doSomeWork.

So why the last message outside the context is still contains MDC values? or I'm missing something?

Solution

  • As mentioned in the one of the comments the issue is discussed in https://github.com/Kotlin/kotlinx.coroutines/issues/985

    It seems that it was fixed in one of the latest releases.