Split out registration to worker

This allows registration to be handled by a worker, though the actual
write to the database still happens on master.

Note: due to the in-memory session map all registration requests must be
handled by the same worker.

synapse/replication/http/login.py

@@ -0,0 +1,85 @@
+# -*- coding: utf-8 -*-
+# Copyright 2019 New Vector Ltd
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import logging
+
+from twisted.internet import defer
+
+from synapse.http.servlet import parse_json_object_from_request
+from synapse.replication.http._base import ReplicationEndpoint
+
+logger = logging.getLogger(__name__)
+
+
+class RegisterDeviceReplicationServlet(ReplicationEndpoint):
+    """Ensure a device is registered, generating a new access token for the
+    device.
+
+    Used during registration and login.
+    """
+
+    NAME = "device_check_registered"
+    PATH_ARGS = ("user_id",)
+
+    def __init__(self, hs):
+        super(RegisterDeviceReplicationServlet, self).__init__(hs)
+        self.auth_handler = hs.get_auth_handler()
+        self.device_handler = hs.get_device_handler()
+        self.macaroon_gen = hs.get_macaroon_generator()
+
+    @staticmethod
+    def _serialize_payload(user_id, device_id, initial_display_name, is_guest):
+        """
+        Args:
+            device_id (str|None): Device ID to use, if None a new one is
+                generated.
+            initial_display_name (str|None)
+            is_guest (bool)
+        """
+        return {
+            "device_id": device_id,
+            "initial_display_name": initial_display_name,
+            "is_guest": is_guest,
+        }
+
+    @defer.inlineCallbacks
+    def _handle_request(self, request, user_id):
+        content = parse_json_object_from_request(request)
+
+        device_id = content["device_id"]
+        initial_display_name = content["initial_display_name"]
+        is_guest = content["is_guest"]
+
+        device_id = yield self.device_handler.check_device_registered(
+            user_id, device_id, initial_display_name,
+        )
+
+        if is_guest:
+            access_token = self.macaroon_gen.generate_access_token(
+                user_id, ["guest = true"]
+            )
+        else:
+            access_token = yield self.auth_handler.get_access_token_for_user_id(
+                user_id, device_id=device_id,
+            )
+
+        defer.returnValue((200, {
+            "device_id": device_id,
+            "access_token": access_token,
+        }))
+
+
+def register_servlets(hs, http_server):
+    RegisterDeviceReplicationServlet(hs).register(http_server)