Question

For a super-basic http twisted front-end.
How can I make sure no html is ever written back unless I tell it to.

So, I have my /zoo url below.
For any tracebacks, or ‘No Such Resource’ responses, I want to just drop the connection or return an empty response.

I guess it’s a super-simple one but can’t figure it out 🙂
I know I could do it byt not having my specific Child path, but want to do it efficient, would just want to drop it as early as possible.. Maybe not use Resource?

class HttpApi(resource.Resource):
    isLeaf = True
    def render_POST(self, request):
        return "post..."


application = service.Application("serv")

json_api = resource.Resource()
json_api.putChild("zoo", HttpApi())
web_site = server.Site(json_api)
internet.TCPServer(8001, web_site).setServiceParent(application)

Answer 1

Some basics first

The way twisted.web works is

There is class called Site which is a HTTP factory.
This is called for every request. In fact, a function called getResourceFor is called to obtain the appropriate resource that will serve this request.
This Site class is initialized with root resource. And the function Site.getResourceFor calls resource.getChildForRequest on the root resource

Call flow is:

Site.getResourceFor -> resource.getChildForRequest (root resource)

Now it is time to look at getChildForRequest:

def getChildForRequest(resource, request):
    """
    Traverse resource tree to find who will handle the request.
    """
    while request.postpath and not resource.isLeaf:
        pathElement = request.postpath.pop(0)
        request.prepath.append(pathElement)
        resource = resource.getChildWithDefault(pathElement, request)
    return resource

What happens is as resources are registered with putChild(path), they become child resources of that resource.
An example:

root_resource
|
|------------ resource r1 (path = 'help')
|----resource r2 (path = 'login')  |
|                                  |----- resource r3 (path = 'registeration')
|                                  |----- resource r4 (path = 'deregistration')

Some reflections:

1. Now r1 will server request with path http://../help/
2. Now r3 will server request with path http://../help/registration/
3. Now r4 will server request with path http://../help/deregistration/

But

1. r3 will server request with path http://../help/registration/xxx/
2. r3 will server request with path http://../help/registration/yyy/

For the solution:

You will need to subclass Site to

1. check if the path excatly matches the resource returned with pathElement empty and only then process it or
2. return a resource which will be your handler to handle other aspects

You will have to create your own resource

def render(self, request):
    request.setResponseCode(...)
    return ""