How to do some cleanup after the client closes the connection - scala

Question

I'm creating a proxy API using akka that does some preparations before forwarding the request to the actual API. For one of the endpoints, the response is streaming json data and the client may close the connection at any time. Akka seems to handle this automatically, but the issue is I need to do some cleanup after the client closes the connection.
path("query") {
post {
decodeRequest {
entity(as[Query]) { query =>
// proxy does some preparations
val json: String = query.prepared.toJson.toString()
// proxy sends request to actual server
val request = HttpRequest(
method = HttpMethods.POST,
uri = serverUrl + "/query",
entity = HttpEntity(ContentTypes.`application/json`, json)
)
val responseFuture = Http().singleRequest(request)
val response: HttpResponse = Await.result(responseFuture, PROXY_TIMEOUT)
// proxy forwards server's response to user
complete(response)
}
}
}
}
I've tried doing something like
responseFuture.onComplete(_ => doCleanup())
But that doesn't work because responseFuture completes immediately even though the server continues to send data until the client closes the connection. complete(response) also returns immediately.
So I'm wondering how I can make a call to doCleanup() only after the client has closed the connection.
Edit: The cleanup I need to do is because the proxy creates some data streams that are meant to be temporary and only persist until the last message is sent by the server. Once that happens these streams need to be deleted.

Answer 1

You can do it with minimal changes to you code like that:
val responseFuture = Http().singleRequest(request)
val response: HttpResponse = try {
Await.result(responseFuture, PROXY_TIMEOUT)
} finally {
doCleanup()
}
complete(response)
or you can do it without blocking:
val responseFuture = Http().singleRequest(request)
val cleaned = responseFuture.andThen{case _ => doCleanUp()}
complete(cleaned) //it's possible to complete response with Future