MSC2197 Search Filters over Federation

changelog.d/5859.feature

@@ -0,0 +1,2 @@
+Add unstable support for MSC2197 (filtered search requests over federation), in
+order to allow upcoming room directory query performance improvements.

synapse/federation/transport/client.py

@@ -327,21 +327,37 @@ def get_public_rooms(
         include_all_networks=False,
         third_party_instance_id=None,
     ):
-        path = _create_v1_path("/publicRooms")
-
-        args = {"include_all_networks": "true" if include_all_networks else "false"}
-        if third_party_instance_id:
-            args["third_party_instance_id"] = (third_party_instance_id,)
-        if limit:
-            args["limit"] = [str(limit)]
-        if since_token:
-            args["since"] = [since_token]
-
-        # TODO(erikj): Actually send the search_filter across federation.
-
-        response = yield self.client.get_json(
-            destination=remote_server, path=path, args=args, ignore_backoff=True
-        )
+        if search_filter:
+            # TODO(MSC2197): Move to V1 prefix
+            path = _create_path(FEDERATION_UNSTABLE_PREFIX, "/publicRooms")
+
+            data = {"include_all_networks": "true" if include_all_networks else "false"}
+            if third_party_instance_id:
+                data["third_party_instance_id"] = third_party_instance_id
+            if limit:
+                data["limit"] = str(limit)
+            if since_token:
+                data["since"] = since_token
+
+            data["filter"] = search_filter
+
+            response = yield self.client.post_json(
+                destination=remote_server, path=path, data=data, ignore_backoff=True
+            )
+        else:
+            path = _create_v1_path("/publicRooms")
+
+            args = {"include_all_networks": "true" if include_all_networks else "false"}
+            if third_party_instance_id:
+                args["third_party_instance_id"] = (third_party_instance_id,)
+            if limit:
+                args["limit"] = [str(limit)]
+            if since_token:
+                args["since"] = [since_token]
+
+            response = yield self.client.get_json(
+                destination=remote_server, path=path, args=args, ignore_backoff=True
+            )
 
         return response
 

synapse/federation/transport/server.py

@@ -751,6 +751,64 @@ async def on_GET(self, origin, content, query):
         return 200, data
 
 
+class UnstablePublicRoomList(BaseFederationServlet):
+    """
+    Fetch the public room list for this server.
+
+    This API returns information in the same format as /publicRooms on the
+    client API, but will only ever include local public rooms and hence is
+    intended for consumption by other home servers.
+
+    This is the unstable-prefixed version which adds support for MSC2197, which
+    is still undergoing review.
+    """
+
+    PATH = "/publicRooms"
+    PREFIX = FEDERATION_UNSTABLE_PREFIX
+
+    def __init__(self, handler, authenticator, ratelimiter, server_name, allow_access):
+        super(UnstablePublicRoomList, self).__init__(
+            handler, authenticator, ratelimiter, server_name
+        )
+        self.allow_access = allow_access
+
+    # TODO(MSC2197): Move away from Unstable prefix and back to normal prefix
+    async def on_POST(self, origin, content, query):
+        if not self.allow_access:
+            raise FederationDeniedError(origin)
+
+        limit = int(content.get("limit", 100))
+        since_token = content.get("since", None)
+        search_filter = content.get("filter", None)
+
+        include_all_networks = content.get("include_all_networks", False)
+        third_party_instance_id = content.get("third_party_instance_id", None)
+
+        if include_all_networks:
+            network_tuple = None
+            if third_party_instance_id is not None:
+                raise SynapseError(
+                    400, "Can't use include_all_networks with an explicit network"
+                )
+        elif third_party_instance_id is None:
+            network_tuple = ThirdPartyInstanceID(None, None)
+        else:
+            network_tuple = ThirdPartyInstanceID.from_string(third_party_instance_id)
+
+        if search_filter is None:
+            logger.warning("Nonefilter")
+
+        data = await self.handler.get_local_public_room_list(
+            limit=limit,
+            since_token=since_token,
+            search_filter=search_filter,
+            network_tuple=network_tuple,
+            from_federation=True,
+        )
+
+        return 200, data
+
+
 class FederationVersionServlet(BaseFederationServlet):
     PATH = "/version"
 
@@ -1315,7 +1373,7 @@ async def on_GET(self, origin, content, query, room_id):
 
 OPENID_SERVLET_CLASSES = (OpenIdUserInfo,)
 
-ROOM_LIST_CLASSES = (PublicRoomList,)
+ROOM_LIST_CLASSES = (PublicRoomList, UnstablePublicRoomList)
 
 GROUP_SERVER_SERVLET_CLASSES = (
     FederationGroupsProfileServlet,

synapse/handlers/room_list.py

@@ -25,6 +25,7 @@
 from twisted.internet import defer
 
 from synapse.api.constants import EventTypes, JoinRules
+from synapse.api.errors import Codes, HttpResponseException
 from synapse.types import ThirdPartyInstanceID
 from synapse.util.async_helpers import concurrently_execute
 from synapse.util.caches.descriptors import cachedInlineCallbacks
@@ -485,7 +486,33 @@ def get_remote_public_room_list(
             return {"chunk": [], "total_room_count_estimate": 0}
 
         if search_filter:
-            # We currently don't support searching across federation, so we have
+            # Searching across federation is defined in MSC2197.
+            # However, the remote homeserver may or may not actually support it.
+            # So we first try an MSC2197 remote-filtered search, then fall back
+            # to a locally-filtered search if we must.
+
+            try:
+                res = yield self._get_remote_list_cached(
+                    server_name,
+                    limit=limit,
+                    since_token=since_token,
+                    include_all_networks=include_all_networks,
+                    third_party_instance_id=third_party_instance_id,
+                    search_filter=search_filter,
+                )
+                return res
+            except HttpResponseException as hre:
+                syn_err = hre.to_synapse_error()
+                if hre.code in (404, 405) or syn_err.errcode in (
+                    Codes.UNRECOGNIZED,
+                    Codes.NOT_FOUND,
+                ):
+                    logger.debug("Falling back to locally-filtered /publicRooms")
+                else:
+                    raise  # Not an error that should trigger a fallback.
+
+            # if we reach this point, then we fall back to the situation where
+            # we currently don't support searching across federation, so we have
             # to do it manually without pagination
             limit = None
             since_token = None