Analytics API

[swankjesse]

We should add verbose logging for the response cache. Folks occasionally are puzzled when the cache doesn't work. Let's make it easy for them to figure out why.

It would also be handy for debug panels and optimizers to monitor bytes in and out, connections created, etc.

[realdadfish]

It would be great if okhttp would in general get a simple logging facility to see what is actually sent and received over the wire.

[swankjesse]

Also logging connection reuse should be helpful.

[codefromthecrypt]

I'd like to see overall overhead (bytes/ms) per request/response since w/SPDY, HTTP2 compression could dramatically impact things.

[swankjesse]

Strawman:

interface Observer {
  void before(Event event);
  void after(Event event);

  public class Event {
    public Type type;
    public Connection connection;
    public Request request;
    public Response response;
    public int bytesTransmitted;
  }

  public enum Type {
    CONNECT,
    DISCONNECT,
    REQUEST_HEADERS,
    REQUEST_BODY,
    RESPONSE_HEADERS,
    RESPONSE_BODY,
  }
}

We'd call the observer before and after we attempt to do I/O. Fields in Event would be populated as much as convenient: bytesTransmitted wouldn't be populated in BEFORE events, for example.

The application layer could plug into this to do logging or higher-level things.

[JakeWharton]

Connection is mutable so should we expose it?

[swankjesse]

Connection is the easiest way to get access to the Route, the Handshake and eventually the Protocol. We have an awkward time with the seam between public and internal APIs in OkHttp.