Contextual data for proxied request

[tsegismont]

We should have the ability to provide some contextual data when handing over a request to the proxy.

This data should be accessible to all the different proxy components (e.g. origin selector, interceptors).

Possibly related to #35 and #44

[fbuetler]

Might be related https://github.com/eclipse-vertx/vertx-http-proxy/issues/50

[tsegismont]

Thanks for the heads-up @fbuetler

[wzy1935]

I pushed an example implementation #96, using a wrapper (indeed I think HttpServerRequestWrapper is the most decent approach) so that context can bind to each request.

Usage example:

// Before
vertx.createHttpServer().requestHandler(proxy);

// After
vertx.createHttpServer().requestHandler(request -> {
  ContextedHttpServerRequest contextedRequest = ContextedHttpServerRequest.from(request);
  contextedRequest.set("key", "value");
  proxy.handle(contextedRequest);
});

What do you think? @tsegismont

[tsegismont]

Thanks for your proposal @wzy1935

I'm not sure we should pursue in this direction. We already have a mechanism for extended HTTP request in Vert.x Web. I don't think it's a good thing to do the same in Vert.x core (which doesn't have the need for this).

[wzy1935]

I think the additional context data must be passed through the HttpProxy#handle(HttpServerRequest request) method (since we want it to be per request), but I also think that HttpProxy should still extends Handler<HttpServerRequest>, so It's kinda troublesome. Can we based on this one https://github.com/eclipse-vertx/vertx-http-proxy/pull/96/commits/f95ac839bb776209e26c64cda33701d482652b9d ? It will also allow user to create/pass their own context instance.

(I think I'm running out of ideas)

[tsegismont]

I think the additional context data must be passed through the HttpProxy#handle(HttpServerRequest request) method (since we want it to be per request), but I also think that HttpProxy should still extends Handler<HttpServerRequest>, so It's kinda troublesome. Can we based on this one f95ac83 ? It will also allow user to create/pass their own context instance.

This looks to be going in the right direction, in my opinion. We can still have HttpProxy extending Handler<HttpServerRequest>. By default, the contextual data map will be empty.

And then, like in your prototype, the HttpProxy can have an overloaded method:

  /**
   * Handle the <i><b>outbound</b></i> {@code HttpServerRequest}.
   *
   * @param request the outbound {@code HttpServerRequest}
   */
  void handle(HttpServerRequest request, Map<String, Object> attachments);

We can use the existing concept of attachments to the ProxyContext.

Next step is to overoload (and maybe deprecate) the originSelector and originRequestProvider methods so that the user can retrieve an attachment when the callback is invoked.