Anyone knows how the top-level

fold

handles

TimeoutCancellationException

s? It seems like they're rethrown... but in Ktor, I'd like to use it to return some kind of timeout response to the client... (I suspect that Ktor just hangs w/o some kind of timeout in certain situations...)

you could use

withTimeoutOrNull

... not such a nice hack there with

?: ""

private suspend inline fun KtorCtx.respond(
    statusCode: HttpStatusCode,
    noinline action: suspend Raise<ErrorContext>.() -> String
): Unit = fold(
    {
        withTimeoutOrNull(5.seconds) {
            action()
        }?.also { call.respond(RequestTimeout) } ?: ""
    },
    { error ->
        val jsonError = Json.encodeToString(error)
        call.respond(BadRequest, error.toString())
        application.log.error(jsonError)
    }) { a ->
        call.respondText(a, ContentType.Application.Json, statusCode)
    }

This is because

TimeoutCancellation

inherits from

CancellationException

. There is some discussion on KotlinX Coroutines to change this, but it’s a binar breaking change. They might change this is 2.0, but you can use

withTimeoutOrNull

& custom exception or Java’s

TimeoutException