Server logging middleware: change logAction to F[String => F[Unit]]
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iRevive
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May 15, 2024
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| val logF: IO[String => IO[Unit]] = | ||
| for { | ||
| state <- local.get | ||
| } yield (message: String) => logs.update(_ :+ (message, state)) |
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This test fails on the current main branch.
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iRevive
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May 15, 2024
| @@ -39,11 +39,11 @@ object Logger { | |||
| logBody: Boolean, | |||
| fk: F ~> G, | |||
| redactHeadersWhen: CIString => Boolean = defaultRedactHeadersWhen, | |||
| logAction: Option[String => F[Unit]] = None, | |||
| logAction: Option[F[String => F[Unit]]] = None, | |||
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We can also use something more flexible:
sealed trait LogAction[F[_]]
object LogAction {
def plain[F[_]](f: String => F[Unit]): LogAction[F] = PlainAction(f)
def deferred[F[_]](f: F[String => F[Unit])]: LogAction[F] = DeferredAction(f)
private[http4s] final case class LogAction[F[_]](f: String => F[Unit]) extends LogAction[F]
private[http4s] final case class DeferredAction[F[_]](f: F[String => F[Unit]]) extends LogAction[F]
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Maybe even an implicit conversion can be handy:
implicit def toPlainLogAction[F[_]](f: String => F[Unit]): LogAction[F] = LogAction.plain(f)
implicit def toDeferredLogAction[F[_]](f: F[String => F[Unit]]): LogAction[F] = LogAction.deferred(f)
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The follow-up to https://discord.com/channels/632277896739946517/632286375311573032/1239565715036442686.
Repo example: https://github.com/alexcardell/otel4s-server-logger-repro-example/tree/master
Motivation
We want to allow capturing the 'state' while we are still within Kleisli closure. This is needed to make the MDC logging work.
Context
When
logBody = false, the logging is 'streamlined' - the message will be logged within the Kleisli closure.http4s/server/shared/src/main/scala/org/http4s/server/middleware/ResponseLogger.scala
Lines 79 to 80 in b5cd7d7
However, when
logBody = true, the logic changes drastically. The middleware binds logging action to the materialization of the body.http4s/server/shared/src/main/scala/org/http4s/server/middleware/ResponseLogger.scala
Lines 83 to 89 in b5cd7d7
Since the body's materialization may happen outside of the Kelisli (and/or on a different fiber), the relevant IOLocal context is missing.