How to properly handle exceptions happening on the...

# kotlinx-rpc

[neworldlt]

How to properly handle exceptions happening on the server side? Due to browser limitations, I am sending the token as a URL parameter and doing validation in the server setup, like:

rpc(RpcEndpoints.ADMIN) {
                val rawJwt = call.request.queryParameters[Constants.TOKEN_URL]
                val session = checkAuth(rawJwt)
                //setup services
            }

However, if an exception happens, the client never gets an answer:

val rpcClient = client.rpc { ... }
            println("#1")
            val protectedService = rpcClient.withService<AdminStatusService>()
            println("#2")
            protectedService.currentUser() // suspend function
            println("#3")

Output is:

#1
#2
<Exception from server>
<Timeout>

Is it a bug, or am I doing it totally wrong?

[neworldlt]

Through further experimentation, I noticed that the exception server does not send any messages; instead, it closes the connection. Then I tried to listen if connection was alive.

[neworldlt]

However, I found that calling rpcClient.awaitCompletion() too soon returns immediately. I am wondering what the proper way to wait until the client closes is.

[neworldlt]

I'm guessing that this snippet can work only if createNewClient() somehow triggers initialization.

So I ended with:

val job = launch {
                val protectedService = rpcClient.withService<AdminStatusService>()
            }
            rpcClient.webSocketSession.await()
            rpcClient.awaitCompletion()
            job.cancel(CancellationException("Socket closed"))

[Alexander Sysoev]

However, I found that calling rpcClient.awaitCompletion() too soon returns immediately. I am wondering what the proper way to wait until the client closes is.

That's a good, point, probably it shouldn't

[Alexander Sysoev]

Is it a bug, or am I doing it totally wrong?

Probably a bug and probably this one https://github.com/Kotlin/kotlinx-rpc/pull/505

[neworldlt]

I was reviewing this PR, but my case looks different; I create a client and await immediate without giving a chance to call anything RPC related which triggers callServerStreaming which makes isTransportReady = true. Until it is true awaitCompletion() completes immediate

[neworldlt]

This code could work for my case, but I guess isTransportReady check has some good reasons: https://github.com/Kotlin/kotlinx-rpc/commit/df7b1ce46ec07efda6284a916bf41102330dac61

public suspend fun awaitCompletion() {
        internalScope.coroutineContext.job.join()
    }

[Alexander Sysoev]

Yeah, early return is indeed a different issue, but your original post (and absence of cancellation on currentUser suspension) is about the linked PR

[neworldlt]

Sorry. Yes, it could be fixed. I will let you know after testing. BTW, is there someplace to write this kind of integration test?

[Alexander Sysoev]

Pardon me for the wording, I meant it's an issue on our side, so we'll fix it in 0.10.1