Valid controller return values should be json-serializable objects.

     Sub-classes should catch their exceptions and raise JSONRPCError

     if they want to pass meaningful errors to the client.

     """

    def _get_ip_addr(self, environ):

        return _get_ip(environ)

    def _get_method_args(self):

        """

        Return `self._rpc_args` to dispatched controller method

        chosen by __call__

        """

        return self._rpc_args

    def _dispatch(self, state, remainder=None):

        """

        Parse the request body as JSON, look up the method on the

        controller and if it exists, dispatch to it.

        """

        # Since we are here we should respond as JSON

        response.content_type = 'application/json'

        environ = state.request.environ

        start = time.time()

        ip_addr = self._get_ip_addr(environ)

        self._req_id = None

        if 'CONTENT_LENGTH' not in environ:

            log.debug("No Content-Length")

            raise JSONRPCErrorResponse(retid=self._req_id,

                                       message="No Content-Length in request")

        else:

            length = environ['CONTENT_LENGTH'] or 0

            length = int(environ['CONTENT_LENGTH'])

            log.debug('Content-Length: %s', length)

        if length == 0:

            raise JSONRPCErrorResponse(retid=self._req_id,

                                       message="Content-Length is 0")

        raw_body = environ['wsgi.input'].read(length)

        try:

            json_body = ext_json.loads(raw_body)

        except ValueError as e:

            # catch JSON errors Here

            raise JSONRPCErrorResponse(retid=self._req_id,

                                       message="JSON parse error ERR:%s RAW:%r"

                                                % (e, raw_body))

        # check AUTH based on API key

        try:

            self._req_api_key = json_body['api_key']

            self._req_id = json_body['id']

            self._req_method = json_body['method']

            self._request_params = json_body['args']

            if not isinstance(self._request_params, dict):

                self._request_params = {}

            log.debug('method: %s, params: %s',

                      self._req_method, self._request_params)

        except KeyError as e:

            raise JSONRPCErrorResponse(retid=self._req_id,

                                       message='Incorrect JSON query missing %s' % e)

        # check if we can find this session using api_key

        try:

            u = User.get_by_api_key(self._req_api_key)

            auth_user = AuthUser.make(dbuser=u, ip_addr=ip_addr)

            if auth_user is None:

                raise JSONRPCErrorResponse(retid=self._req_id,

                                           message='Invalid API key')

        except Exception as e:

            raise JSONRPCErrorResponse(retid=self._req_id,

                                       message='Invalid API key')

        request.authuser = auth_user

        request.ip_addr = ip_addr

        self._error = None

        try:

            self._func = self._find_method()

        except AttributeError as e:

            raise JSONRPCErrorResponse(retid=self._req_id,

                                       message=str(e))

        # now that we have a method, add self._req_params to

        # self.kargs and dispatch control to WGIController

        argspec = inspect.getargspec(self._func)

        arglist = argspec[0][1:]

        defaults = [type(arg) for arg in argspec[3] or []]

        default_empty = type(NotImplemented)

        # kw arguments required by this method

                                                  fillvalue=default_empty))

        # This attribute will need to be first param of a method that uses

        # api_key, which is translated to instance of user at that name

        USER_SESSION_ATTR = 'apiuser'

        # get our arglist and check if we provided them as args

        for arg, default in func_kwargs.items():

            if arg == USER_SESSION_ATTR:

                # USER_SESSION_ATTR is something translated from API key and

                # this is checked before so we don't need validate it

                continue

            # skip the required param check if it's default value is

            # NotImplementedType (default_empty)

            if default == default_empty and arg not in self._request_params:

                raise JSONRPCErrorResponse(

                    retid=self._req_id,

                    message='Missing non optional `%s` arg in JSON DATA' % arg,

                )

        extra = set(self._request_params).difference(func_kwargs)

        if extra:

            raise JSONRPCErrorResponse(

                retid=self._req_id,

                message='Unknown %s arg in JSON DATA' %

                        ', '.join('`%s`' % arg for arg in extra),

            )

        self._rpc_args = {}

        self._rpc_args.update(self._request_params)

        self._rpc_args['action'] = self._req_method

        self._rpc_args['environ'] = environ

        log.info('IP: %s Request to %s time: %.3fs' % (

            self._get_ip_addr(environ),

            get_path_info(environ), time.time() - start)

        )

        state.set_action(self._rpc_call, [])

        state.set_params(self._rpc_args)

        return state

    def _rpc_call(self, action, environ, **rpc_args):

        """

        Call the specified RPC Method

        """

        raw_response = ''

        try:

            raw_response = getattr(self, action)(**rpc_args)

            if isinstance(raw_response, HTTPError):

                self._error = str(raw_response)

        except JSONRPCError as e:

            self._error = unicode(e)

        except Exception as e:

            log.error('Encountered unhandled exception: %s',

                      traceback.format_exc(),)

            json_exc = JSONRPCError('Internal server error')

            self._error = unicode(json_exc)

        if self._error is not None:

            raw_response = None

        response = dict(id=self._req_id, result=raw_response, error=self._error)

        try:

            return ascii_bytes(ext_json.dumps(response))

        except TypeError as e:

            log.error('API FAILED. Error encoding response for %s %s: %s\n%s', action, rpc_args, e, traceback.format_exc())

            return ascii_bytes(ext_json.dumps(

                dict(

                    id=self._req_id,

                    result=None,

                    error="Error encoding response",

                )

            ))

    def _find_method(self):

        """

        Return method named by `self._req_method` in controller if able

        """

        log.debug('Trying to find JSON-RPC method: %s', self._req_method)

        if self._req_method.startswith('_'):

            raise AttributeError("Method not allowed")

        try:

            func = getattr(self, self._req_method, None)

        except UnicodeEncodeError:

            raise AttributeError("Problem decoding unicode in requested "

                                 "method name.")

        if isinstance(func, types.MethodType):

            return func

        else:

            raise AttributeError("No such method: %s" % (self._req_method,))