Expose ackInbox from Message

[gunnaringe]

The only way to acknowledge a message today is by calling Message.ack().

Would it be possible to get hold of the subscription or ackInbox from the message so that we could access it from within the subscription callback?

The background for this is that we are exposing a gRPC API using STAN as a backend, and allow the client of the API to invoke a ack on our side.
Ideally, we would have a method like StreamingConnection.acknowledge() that was triggered by a API call, but creating the ack proto and sending it in the same manner as the Message would also be possible.

Is this something you would consider?

That is basically making Message.getSubscription() public instead of package-private.

[gunnaringe]

To clarify a bit, what I need is to send this message over gRPC and allow the client to send a ack back when this has been processed.

In order to send the required information from the callback handler, we would currently need to fetch this from the subscription after the callback is invoked as it doesn't have access to the subscription nor the ackInbox.

The Kotlin code below would work, but feels more than a bit awkward.

var countDownLatch = CountDownLatch(1)
var ackInbox = ""
val subscription = streamingConnection.subscribe("my-subject") { message ->
    countDownLatch.await()
    process(ackInbox, message.sequence, message.data)
}
ackInbox = subscription.ackInbox
countDownLatch.countDown()

With this change, we could instead do

val subscription = streamingConnection.subscribe("my-subject") { message ->
    process(message.ackInbox, message.sequence, message.data)
}

[sasbury]

i merged your pull request into 2.2.4, once that ships we can close this.