def _process_stack(self, request, action, action_args,
                       content_type, body, accept):
        """Implement the processing stack."""

        # Get the implementing method
        try:
            meth, extensions = self.get_method(request, action,
                                               content_type, body)
        except (AttributeError, __HOLE__):
            return Fault(webob.exc.HTTPNotFound())
        except KeyError as ex:
            msg = _("There is no such action: %s") % ex.args[0]
            return Fault(webob.exc.HTTPBadRequest(explanation=msg))
        except exception.MalformedRequestBody:
            msg = _("Malformed request body")
            return Fault(webob.exc.HTTPBadRequest(explanation=msg))

        if body:
            msg = _("Action: '%(action)s', body: "
                    "%(body)s") % {'action': action,
                                   'body': unicode(body, 'utf-8')}
            LOG.debug(logging.mask_password(msg))
        LOG.debug(_("Calling method '%(meth)s' (Content-type='%(ctype)s', "
                    "Accept='%(accept)s')"),
                  {'meth': str(meth),
                   'ctype': content_type,
                   'accept': accept})

        # Now, deserialize the request body...
        try:
            contents = {}
            if self._should_have_body(request):
                # allow empty body with PUT and POST
                if request.content_length == 0:
                    contents = {'body': None}
                else:
                    contents = self.deserialize(meth, content_type, body)
        except exception.InvalidContentType:
            msg = _("Unsupported Content-Type")
            return Fault(webob.exc.HTTPBadRequest(explanation=msg))
        except exception.MalformedRequestBody:
            msg = _("Malformed request body")
            return Fault(webob.exc.HTTPBadRequest(explanation=msg))

        # Update the action args
        action_args.update(contents)

        project_id = action_args.pop("project_id", None)
        context = request.environ.get('rack.context')
        if (context and project_id and (project_id != context.project_id)):
            msg = _("Malformed request URL: URL's project_id '%(project_id)s'"
                    " doesn't match Context's project_id"
                    " '%(context_project_id)s'") % \
                {'project_id': project_id,
                 'context_project_id': context.project_id}
            return Fault(webob.exc.HTTPBadRequest(explanation=msg))

        # Run pre-processing extensions
        response, post = self.pre_process_extensions(extensions,
                                                     request, action_args)

        if not response:
            try:
                with ResourceExceptionHandler():
                    action_result = self.dispatch(meth, request, action_args)
            except Fault as ex:
                response = ex

        if not response:
            # No exceptions; convert action_result into a
            # ResponseObject
            resp_obj = None
            if type(action_result) is dict or action_result is None:
                resp_obj = ResponseObject(action_result)
            elif isinstance(action_result, ResponseObject):
                resp_obj = action_result
            else:
                response = action_result

            # Run post-processing extensions
            if resp_obj:
                # Do a preserialize to set up the response object
                serializers = getattr(meth, 'wsgi_serializers', {})
                resp_obj._bind_method_serializers(serializers)
                if hasattr(meth, 'wsgi_code'):
                    resp_obj._default_code = meth.wsgi_code
                resp_obj.preserialize(accept, self.default_serializers)

                # Process post-processing extensions
                response = self.post_process_extensions(post, resp_obj,
                                                        request, action_args)

            if resp_obj and not response:
                response = resp_obj.serialize(request, accept,
                                              self.default_serializers)

        if hasattr(response, 'headers'):
            if context:
                response.headers.add('x-compute-request-id',
                                     context.request_id)

            for hdr, val in response.headers.items():
                # Headers must be utf-8 strings
                response.headers[hdr] = utils.utf8(str(val))

        return response
dataset/ETHPy150Open openstack/rack/rack/api/wsgi.py/Resource._process_stack