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.

6 files changed, 37 insertions, 19 deletions

diff --git a/changelog.d/4770.misc b/changelog.d/4770.misc
new file mode 100644
index 0000000000..144d819958
--- /dev/null
+++ b/changelog.d/4770.misc
@@ -0,0 +1 @@
+Optimise EDU transmission for the federation_sender worker.
diff --git a/synapse/federation/send_queue.py b/synapse/federation/send_queue.py
index 6f5995735a..b7d0b25781 100644
--- a/synapse/federation/send_queue.py
+++ b/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)
diff --git a/synapse/federation/transaction_queue.py b/synapse/federation/transaction_queue.py
index 30941f5ad6..e5e42c647d 100644
--- a/synapse/federation/transaction_queue.py
+++ b/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:
diff --git a/synapse/handlers/presence.py b/synapse/handlers/presence.py
index ba3856674d..37e87fc054 100644
--- a/synapse/handlers/presence.py
+++ b/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={
diff --git a/synapse/handlers/receipts.py b/synapse/handlers/receipts.py
index 696469732c..8b2d03a756 100644
--- a/synapse/handlers/receipts.py
+++ b/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={
diff --git a/synapse/handlers/typing.py b/synapse/handlers/typing.py
index a61bbf9392..39df960c31 100644
--- a/synapse/handlers/typing.py
+++ b/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={