Review internals of Starcounter request pipeline about misc

[per-samuelsson]

From Chrome:

GET /foo

Request comes with no headers and text/html as PreferredMimeType, arriving at AppsBootstrapper.ProcessExternalRequest (invoked from gateway).

[per-samuelsson]

First, any request filters are given a chance on the request. No such filters installed.

[per-samuelsson]

With no request filters taking action, the server now give control to the handler, with a call to AppRestServer.RunDelegateAndProcessResponse, that in turn invoke UserHandlerInfo.RunUserDelegate.

In that method, with our setup, we don't have proxy delegate and neither any substitute handler, so finally the call enters our custom, user defined handler that return our Json. When doing so, the implicit cast from Json to Response take place, and by that, the Response produced is referencing our Json as an IResource.

Since StarcounterEnvironment.MergeJsonSiblings is set, the installed Response.ResponsesMergerRoutine_ is now invoked, in our case referencing UriMapping.DefaultJsonMerger. That method doesn't perform any merge, since in our case, we have a single JSON response. It assign the object the app name and sets internal _wrapInAppName to true (not sure what that does).

[per-samuelsson]

Control is now back in AppRestServer.RunDelegateAndProcessResponse after the above detour. We have a Response instance that reference our Json instance, and the server now issue SendResponse on our request object.

[per-samuelsson]

The server now runs any response filters, but in our case, none is registered.

After some global state is transferred to the response object, Response.ConstructFromFields is invoked.

[per-samuelsson]

Response.ConstructFromFields

Builds up the byte[] that are to be sent back to the agent. The array is composed by inspecting the heap data (instance variables) of the current response object.

In our case, the response object reference an IResource instance (our JSON). The response is hence created by asking that instance to return itself as a representation that match the agents preferred MIME type (text/html).