Can a Ktor plugin inject a `CoroutineContext` element into the rest of the pipeline?

# ktor

[CLOVIS]

Can a Ktor plugin inject a CoroutineContext element into the rest of the pipeline?

[Aleksei Tirman [JB]]

You have to intercept a pipeline directly to do that. Here is an example:

class MyElement : CoroutineContext.Element {
    override val key: CoroutineContext.Key<*>
        get() = MyElement

    companion object : CoroutineContext.Key<MyElement>
}

fun main() {
    embeddedServer(Netty, host = "0.0.0.0", port = 12345) {
        sendPipeline.intercept(ApplicationSendPipeline.Before) {
            withContext(coroutineContext + MyElement()) {
                proceed()
            }
        }

        sendPipeline.intercept(ApplicationSendPipeline.Transform) {
            println(coroutineContext[MyElement])
        }

        routing {
            get("/") {
                call.respondText { "OK" }
            }
        }
    }.start(wait = true)
}

[CLOVIS]

Thanks!

[CLOVIS]

It seems to me like ApplicationSendPipeline.Before is executed after call.respondText … which pipeline stage should I use for the context to be available in the route code?

[CLOVIS]

ApplicationCallPipeline.Plugins seems to do the trick