Move client receipt processing to federation sender worker.

This is mostly a prerequisite for #4730, but also fits with the general theme
of "move everything off the master that we possibly can".

synapse/handlers/receipts.py

@@ -16,9 +16,8 @@ import logging
 
 from twisted.internet import defer
 
-from synapse.types import ReadReceipt, get_domain_from_id
-
-from ._base import BaseHandler
+from synapse.handlers._base import BaseHandler
+from synapse.types import ReadReceipt
 
 logger = logging.getLogger(__name__)
 
@@ -87,7 +86,7 @@ class ReceiptsHandler(BaseHandler):
             # no new receipts
             defer.returnValue(False)
 
-        affected_room_ids = list(set([r["room_id"] for r in receipts]))
+        affected_room_ids = list(set([r.room_id for r in receipts]))
 
         self.notifier.on_new_event(
             "receipt_key", max_batch_id, rooms=affected_room_ids
@@ -119,35 +118,7 @@ class ReceiptsHandler(BaseHandler):
         if not is_new:
             return
 
-        # Work out which remote servers should be poked and poke them.
-
-        # TODO: optimise this to move some of the work to the workers.
-        data = receipt.data
-
-        # XXX why does this not use state.get_current_hosts_in_room() ?
-        users = yield self.state.get_current_user_in_room(room_id)
-        remotedomains = set(get_domain_from_id(u) for u in users)
-        remotedomains = remotedomains.copy()
-        remotedomains.discard(self.server_name)
-
-        logger.debug("Sending receipt to: %r", remotedomains)
-
-        for domain in remotedomains:
-            self.federation.build_and_send_edu(
-                destination=domain,
-                edu_type="m.receipt",
-                content={
-                    room_id: {
-                        receipt_type: {
-                            user_id: {
-                                "event_ids": [event_id],
-                                "data": data,
-                            }
-                        }
-                    },
-                },
-                key=(room_id, receipt_type, user_id),
-            )
+        self.federation.send_read_receipt(receipt)
 
     @defer.inlineCallbacks
     def get_receipts_for_room(self, room_id, to_key):