withSmartTags

@ExperimentalMiskApi

fun <T> withSmartTags(vararg tags: Tag, block: () -> T): T

Use this function to add tags to the MDC context for the duration of the block.

This is particularly useful (the smart aspect) when an exception is thrown within the block, the tags can be retrieved outside that block using SmartTagsThreadLocalHandler.popThreadLocalSmartTags() and added to the MDC context again when logging the exception.

Within Misk this is already built into both WebAction (misk.web.exceptions.ExceptionHandlingInterceptor) and misk.jobqueue.sqs.SqsJobConsumer. These can be used as an example to extend for any other incoming "event" consumers within a service such as Kafka, scheduled tasks, temporal workflows, etc.

Usage:

class ServiceAction (private val webClient: WebClient): WebAction {

  @Post("/api/resource")
  fun executeWebAction(@RequestBody request: ServiceActionRequest) {
    logger.info() { "Received request" }

    val loadedContext = aClient.load(request.id)

    withSmartTags(
      "processValue" to request.process_value,
      "contextToken" to loadedContext.token
    ) {
      logger.info() { "Processing request" }
      doSomething()
    }
  }

  private fun doSomething() {
    logger.info() { "Start Process" }

    client.someWebRequest() // Client throws exception which is caught and logged by misk framework

    logger.info() { "Done" }
  }

  companion object {
    val logger = KotlinLogging.logger(ServiceAction::class.java.canonicalName)
  }
}

Logging result:

Log MDC context: [] Log message: "Received request"
Log MDC context: [processValue: "PV_123", contextToken: "contextTokenValue"] Log message: "Processing request"
Log MDC context: [processValue: "PV_123", contextToken: "contextTokenValue"] Log message: "Start Process"
Log MDC context: [processValue: "PV_123", contextToken: "contextTokenValue"] Log message: "unexpected error dispatching to ServiceAction" // This log would not normally include the MDC context