Avoid rebuilding Edu objects in worker mode (#4770)

In worker mode, on the federation sender, when we receive an edu for sending
over the replication socket, it is parsed into an Edu object. There is no point
extracting the contents of it so that we can then immediately build another Edu.

changelog.d/4770.misc

@@ -0,0 +1 @@
+Optimise EDU transmission for the federation_sender worker.

synapse/federation/send_queue.py

@@ -159,8 +159,12 @@ class FederationRemoteSendQueue(object):
         # stream.
         pass
 
-    def send_edu(self, destination, edu_type, content, key=None):
+    def build_and_send_edu(self, destination, edu_type, content, key=None):
         """As per TransactionQueue"""
+        if destination == self.server_name:
+            logger.info("Not sending EDU to ourselves")
+            return
+
         pos = self._next_pos()
 
         edu = Edu(
@@ -465,15 +469,11 @@ def process_rows_for_federation(transaction_queue, rows):
 
     for destination, edu_map in iteritems(buff.keyed_edus):
         for key, edu in edu_map.items():
-            transaction_queue.send_edu(
-                edu.destination, edu.edu_type, edu.content, key=key,
-            )
+            transaction_queue.send_edu(edu, key)
 
     for destination, edu_list in iteritems(buff.edus):
         for edu in edu_list:
-            transaction_queue.send_edu(
-                edu.destination, edu.edu_type, edu.content, key=None,
-            )
+            transaction_queue.send_edu(edu, None)
 
     for destination in buff.device_destinations:
         transaction_queue.send_device_messages(destination)

synapse/federation/transaction_queue.py

@@ -361,7 +361,19 @@ class TransactionQueue(object):
 
                 self._attempt_new_transaction(destination)
 
-    def send_edu(self, destination, edu_type, content, key=None):
+    def build_and_send_edu(self, destination, edu_type, content, key=None):
+        """Construct an Edu object, and queue it for sending
+
+        Args:
+            destination (str): name of server to send to
+            edu_type (str): type of EDU to send
+            content (dict): content of EDU
+            key (Any|None): clobbering key for this edu
+        """
+        if destination == self.server_name:
+            logger.info("Not sending EDU to ourselves")
+            return
+
         edu = Edu(
             origin=self.server_name,
             destination=destination,
@@ -369,18 +381,23 @@ class TransactionQueue(object):
             content=content,
         )
 
-        if destination == self.server_name:
-            logger.info("Not sending EDU to ourselves")
-            return
+        self.send_edu(edu, key)
 
+    def send_edu(self, edu, key):
+        """Queue an EDU for sending
+
+        Args:
+            edu (Edu): edu to send
+            key (Any|None): clobbering key for this edu
+        """
         if key:
             self.pending_edus_keyed_by_dest.setdefault(
-                destination, {}
+                edu.destination, {}
             )[(edu.edu_type, key)] = edu
         else:
-            self.pending_edus_by_dest.setdefault(destination, []).append(edu)
+            self.pending_edus_by_dest.setdefault(edu.destination, []).append(edu)
 
-        self._attempt_new_transaction(destination)
+        self._attempt_new_transaction(edu.destination)
 
     def send_device_messages(self, destination):
         if destination == self.server_name:

synapse/handlers/presence.py

@@ -816,7 +816,7 @@ class PresenceHandler(object):
         if self.is_mine(observed_user):
             yield self.invite_presence(observed_user, observer_user)
         else:
-            yield self.federation.send_edu(
+            yield self.federation.build_and_send_edu(
                 destination=observed_user.domain,
                 edu_type="m.presence_invite",
                 content={
@@ -836,7 +836,7 @@ class PresenceHandler(object):
         if self.is_mine(observer_user):
             yield self.accept_presence(observed_user, observer_user)
         else:
-            self.federation.send_edu(
+            self.federation.build_and_send_edu(
                 destination=observer_user.domain,
                 edu_type="m.presence_accept",
                 content={
@@ -848,7 +848,7 @@ class PresenceHandler(object):
             state_dict = yield self.get_state(observed_user, as_event=False)
             state_dict = format_user_presence_state(state_dict, self.clock.time_msec())
 
-            self.federation.send_edu(
+            self.federation.build_and_send_edu(
                 destination=observer_user.domain,
                 edu_type="m.presence",
                 content={

synapse/handlers/receipts.py

@@ -148,7 +148,7 @@ class ReceiptsHandler(BaseHandler):
             logger.debug("Sending receipt to: %r", remotedomains)
 
             for domain in remotedomains:
-                self.federation.send_edu(
+                self.federation.build_and_send_edu(
                     destination=domain,
                     edu_type="m.receipt",
                     content={

synapse/handlers/typing.py

@@ -231,7 +231,7 @@ class TypingHandler(object):
             for domain in set(get_domain_from_id(u) for u in users):
                 if domain != self.server_name:
                     logger.debug("sending typing update to %s", domain)
-                    self.federation.send_edu(
+                    self.federation.build_and_send_edu(
                         destination=domain,
                         edu_type="m.typing",
                         content={