Provide a better way to modify `CoroutineContext` in `RequestContext`

Just an idea.

Currently, Armeria provides following ways to get & set CoroutineContext that will later be used to run a coroutine-based AnnotatedService:

• CoroutineContexts#get, CoroutineContexts#set
• CoroutineContextService with CoroutineContextProvider

…but I find CoroutineContextService and CoroutineContextProvider a bit redundant as what can be done with them can also be done with CoroutineContexts#get/set while the opposite is not true.

And non of those APIs provide a convenient way to combine(+) a new CoroutineContext with the one added earlier as CoroutineContexts#set just overwrites the whole CoroutineContext with the new one.

We may want to provide cleaner APIs to get/set CoroutineContext in a RequestContext by adding following extension functions & property, if there’s no good reason to write those APIs in Java.

fun RequestContext.addCoroutineContext(ctx: CoroutineContext): Unit

fun RequestContext.removeCoroutineContext(ctx: CoroutineContext): Unit

var RequestContext.coroutineContext: CoroutineContext?
    get() = ...
    set(value) = ...

[ks-yim]

@ikhoon The approach you’ve suggested will prevent unnecessary confusion, thanks! I will send a PR to add a new method to CoroutineContexts.

[minwoox]

We often just do the following in an Authorizer<HttpRequest> to add authenticated user context to the coroutine

Yeah, if there’s another decorator that we can set a CoroutineContext, we don’t need the CoroutineContextService decorator. But we do need CoroutineContextService if there’s no decorator like this example: https://github.com/line/armeria/blob/master/examples/annotated-http-service-kotlin/src/main/kotlin/example/armeria/server/annotated/kotlin/DecoratingService.kt#L53-L55

but I am suggesting the same functionality can be provided with more kotlin-friend APIs by leveraging kotlin’s extension function & property (refer to the code written in my initial comment).

I agree with you on this. 👍 What I meant was that we need a way to set/add a CoroutinContext to RequestContext in a decorator. It doesn’t have to be CoroutineContexts#get/set if there are better ones. And the design looks nice. Are you sending a PR for that? 😆

More specifically, let’s say we want to store 1) AuthN/Z context and 2) DB’s shard-routine context within 2 different decorators

That’s a possible scenario. 👍

this wouldn’t be an issue if I stick strictly to CoroutineContextService & CoroutineContextProvider approach, but then

We didn’t have to stick to CoroutineContextService and CoroutineContextProvider from the first. 😆 It’s just a way to set the CoroutineContext. We can use another decorator and set CoroutineContext directly in it.

/cc @okue