Apply contextCapture automatically in await function

[be-hase]

Motivation

This is a similar issue.
#3406

For users using kotlin coroutine, ThreadContextElement is used to propagate MDC, etc.

The block operator is supported by Hooks.automaticContextPropagation, but not the await function. Therefore, we are forced to write it this way.

// e.g. WebClient

webClient.post()
    .uri("...")
    // omitted
    .contextCapture()
    .awaitSingle()

It would be great if the await function is also supported, like the block operator.

...However, the await function is implemented on the coroutine side, so perhaps a request should be made on the coroutine side.
https://github.com/Kotlin/kotlinx.coroutines/blob/1ccc96890d38be52d1bdcd31af5befb54804aa05/reactive/kotlinx-coroutines-reactor/src/Mono.kt#L46

Desired solution

Considered alternatives

Additional context

[be-hase]

Sorry, I was wrong in my verification and the problem did not occur even with await.
I'll close this issue.
reopend issue.

[be-hase]

I have created a sample project.
https://github.com/be-hase/context-propagation-report-202309/tree/main/coroutines-issue

The code is in one file.
https://github.com/be-hase/context-propagation-report-202309/blob/main/coroutines-issue/src/main/kotlin/example/CoroutinesIssueApplication.kt

You can start it with the following command.

./gradlew :coroutines-issue:bootRun 

[be-hase]

I found that the following workaround can be done using the ContextInjector mechanism provided by the coroutines side.

• https://github.com/Kotlin/kotlinx.coroutines/blob/7e2d23740c71b8ec5a7e2440f02b36e0519496a6/reactive/kotlinx-coroutines-reactive/src/ContextInjector.kt
• https://github.com/Kotlin/kotlinx.coroutines/blob/7e2d23740c71b8ec5a7e2440f02b36e0519496a6/reactive/kotlinx-coroutines-reactor/src/Mono.kt#L47

package example

import kotlinx.coroutines.InternalCoroutinesApi
import kotlinx.coroutines.reactive.ContextInjector
import org.reactivestreams.Publisher
import reactor.core.publisher.Flux
import reactor.core.publisher.Mono
import kotlin.coroutines.CoroutineContext

@OptIn(InternalCoroutinesApi::class)
class ContextCaptureInjector : ContextInjector {
    override fun <T> injectCoroutineContext(publisher: Publisher<T>, coroutineContext: CoroutineContext): Publisher<T> {
        return when (publisher) {
            is Mono -> publisher.contextCapture()
            is Flux -> publisher.contextCapture()
            else -> publisher
        }
    }
}

[OlegDokuka]

@be-hase please move reopen this ticket at kotlin side since we can nothing to do at the reactor one. Alternatively, the mentioned workaround could be landed there -> https://github.com/reactor/reactor-kotlin-extensions.

Feel free to open PR

[be-hase]

OK, I'll reopen issue. thanks :)

[be-hase]

reopend here: reactor/reactor-kotlin-extensions#59