gistfile1.py

class Local:
    def __getattr__(self, attr):
        # finds 'attr' stored for the current Task.context_id

    def __setattr__(self, attr, val):
        # stores value for the current Task.context_id

local = Local()


@contextmanager
def trace(msg):
    # ... time a code block, and store results
    # somewhere


def get_traces(context_id):
    # return accumulated traces for the current Task.context_id


class HttpProtocol(Protocol):
    def connection_made(self, transport):
        request_id = uuid.uuid4()
        self._worker = asyncio.Task(self.on_request(),
                                    context_id=request_id)

        self._worker.add_done_callback(submit_traces, request_id)

    def submit_traces(self, request_id):
        traces = get_traces(request_id)
        submit_traces_to_newrelic(traces)

    @coroutine
    def on_request(self):
        local.transport_info = transport.get_extra_info(...)

        with trace('http request pasing'):
            request = yield from parse_request()

        response = HttpResponse()
        yield from self.dispatch_request(request, response)

    @coroutine
    def dispatch_request(self, request, response):
        # ... route `request` & `response` objects to an
        # http request handler


class DBConnection:
    @coroutine
    def query(self, query, **args):
        with trace('db query'):
            # bunch of `yield from`s to DB driver


class Template:
    def render(self, *args):
        with trace('template rendering'):
            # some template engine stuff

            ip = local.transport_info.remote_addr
            # render user's IP address

            # ...
            return rendered_html


@app.route('/')
@coroutine
def index(request, response):
    db = DBConnection()
    result = yield from db.query('select 1')
    html = template.render(result)
    response.add_header('content-type', 'html')
    return html