Showcase

One request, event by event

A server and an application say four things to each other, or a dozen. Here they are in the order they happen, for nine shapes of traffic, recorded from real runs of this library.

Play a request

Reading the lanes

Each card is one event. The label on the left is the lane it travelled in:

Nothing in the middle lane crosses the seam. It is there to show where the application was when the events around it happened, which is the part a protocol trace usually hides.

How it was recorded

src/examples/18-trace builds each scenario the way an application would, then drives it with a receive and a send that write down what passes through them. The timeline on this page is that transcript, nothing else.

fn Driver::receive(self : Driver) -> @spec.Receive {
  async fn() {
    let event = self.inbound[self.at]
    self.at = self.at + 1
    self.rec.add("in", event_title(event), event_body(event), "the application pulls it in")
    event
  }
}

fn Driver::send(self : Driver) -> @spec.Send {
  async fn(event) {
    self.out.push(event)
    self.rec.add("out", event_title(event), event_body(event), "the application pushes it out")
  }
}

Because the recording happens at the seam itself, the order is the application's own: a streamed body shows three pulls and one push, a middleware stack shows the request entering every layer and the answer leaving through them in reverse.