Using configure script with Ktor 3 CoroutineScope.embeddedServer extension function

I am using Ktor 3.x and am looking to start an embedded server using the Coroutine scope extension function, while also supplying my own configure script.

The documentation I am referencing is here.

As we can see from the function signature, there exists one which allows you to pass your own configure: TConfiguration.() -> Unit = {}.

fun <TEngine : ApplicationEngine, TConfiguration : ApplicationEngine.Configuration> embeddedServer(
    factory: ApplicationEngineFactory<TEngine, TConfiguration>, 
    environment: ApplicationEnvironment = applicationEnvironment(), 
    configure: TConfiguration.() -> Unit = {}, 
    module: Application.() -> Unit = {}
): EmbeddedServer<TEngine, TConfiguration>

Observing the extension functions from CoroutineScope, they do not allow us to pass a configure block:

fun <TEngine : ApplicationEngine, TConfiguration : ApplicationEngine.Configuration> CoroutineScope.embeddedServer(
    factory: ApplicationEngineFactory<TEngine, TConfiguration>, 
    vararg connectors: EngineConnectorConfig = arrayOf(), 
    watchPaths: List<String> = listOf(WORKING_DIRECTORY_PATH), 
    parentCoroutineContext: CoroutineContext = EmptyCoroutineContext, 
    module: Application.() -> Unit
): EmbeddedServer<TEngine, TConfiguration>

fun <TEngine : ApplicationEngine, TConfiguration : ApplicationEngine.Configuration> CoroutineScope.embeddedServer(
    factory: ApplicationEngineFactory<TEngine, TConfiguration>, 
    port: Int = 80, 
    host: String = "0.0.0.0", 
    watchPaths: List<String> = listOf(WORKING_DIRECTORY_PATH), 
    parentCoroutineContext: CoroutineContext = EmptyCoroutineContext, 
    module: Application.() -> Unit
): EmbeddedServer<TEngine, TConfiguration>

What is the expected way to gain the configure functionality when working with the extension function?

Solution

Unfortunately, there is no way to configure the engine while using the CoroutineScope.embeddedServer method. However, you can define your own overloaded method, which would allow that:

fun <TEngine : ApplicationEngine, TConfiguration : ApplicationEngine.Configuration> CoroutineScope.embeddedServer(
    factory: ApplicationEngineFactory<TEngine, TConfiguration>,
    environment: ApplicationEnvironment = applicationEnvironment(),
    configure: TConfiguration.() -> Unit = {},
    module: Application.() -> Unit = {}
): EmbeddedServer<TEngine, TConfiguration> {
    val applicationProperties = serverConfig(environment) {
        this.parentCoroutineContext = coroutineContext + parentCoroutineContext
        this.module(module)
    }

    return embeddedServer(factory, applicationProperties, configure)
}

Here is an example of the method usage:

CoroutineScope(Dispatchers.IO).embeddedServer(
    Netty,
    applicationEnvironment {},
    configure = {
        maxHeaderSize = 1024 * 1024
        connectors.add(EngineConnectorBuilder().withPort(8833))
    }
) {
    routing {
        get {
            call.respondText("Hello World!")
        }
    }
}.start(wait = true)