Use event streams to calculate presence

Primarily this fixes a bug in the handling of remote users joining a
room where the server sent out the presence for all local users in the
room to all servers in the room.

We also change to using the state delta stream, rather than the
distributor, as it will make it easier to split processing out of the
master process (as well as being more flexible).

Finally, when sending presence states to newly joined servers we filter
out old presence states to reduce the number sent. Initially we filter
out states that are offline and have a last active more than a week ago,
though this can be changed down the line.

Fixes #3962

1 files changed, 18 insertions, 1 deletions

diff --git a/synapse/federation/sender/__init__.py b/synapse/federation/sender/__init__.py
index 1dc041752b..4f0f939102 100644
--- a/synapse/federation/sender/__init__.py
+++ b/synapse/federation/sender/__init__.py
@@ -371,7 +371,7 @@ class FederationSender(object):
             return
 
         # First we queue up the new presence by user ID, so multiple presence
-        # updates in quick successtion are correctly handled
+        # updates in quick succession are correctly handled.
         # We only want to send presence for our own users, so lets always just
         # filter here just in case.
         self.pending_presence.update({
@@ -402,6 +402,23 @@ class FederationSender(object):
         finally:
             self._processing_pending_presence = False
 
+    def send_presence_to_destinations(self, states, destinations):
+        """Send the given presence states to the given destinations.
+
+        Args:
+            states (list[UserPresenceState])
+            destinations (list[str])
+        """
+
+        if not states or not self.hs.config.use_presence:
+            # No-op if presence is disabled.
+            return
+
+        for destination in destinations:
+            if destination == self.server_name:
+                continue
+            self._get_per_destination_queue(destination).send_presence(states)
+
     @measure_func("txnqueue._process_presence")
     @defer.inlineCallbacks
     def _process_presence_inner(self, states):