Port synapse.replication.tcp to async/await (#6666)

* Port synapse.replication.tcp to async/await

* Newsfile

* Correctly document type of on_<FOO> functions as async

* Don't be overenthusiastic with the asyncing....

synapse/replication/tcp/protocol.py

@@ -81,12 +81,11 @@ from synapse.replication.tcp.commands import (
     SyncCommand,
     UserSyncCommand,
 )
+from synapse.replication.tcp.streams import STREAMS_MAP
 from synapse.types import Collection
 from synapse.util import Clock
 from synapse.util.stringutils import random_string
 
-from .streams import STREAMS_MAP
-
 connection_close_counter = Counter(
     "synapse_replication_tcp_protocol_close_reason", "", ["reason_type"]
 )
@@ -241,19 +240,16 @@ class BaseReplicationStreamProtocol(LineOnlyReceiver):
             "replication-" + cmd.get_logcontext_id(), self.handle_command, cmd
         )
 
-    def handle_command(self, cmd):
+    async def handle_command(self, cmd: Command):
         """Handle a command we have received over the replication stream.
 
-        By default delegates to on_<COMMAND>
+        By default delegates to on_<COMMAND>, which should return an awaitable.
 
         Args:
-            cmd (synapse.replication.tcp.commands.Command): received command
-
-        Returns:
-            Deferred
+            cmd: received command
         """
         handler = getattr(self, "on_%s" % (cmd.NAME,))
-        return handler(cmd)
+        await handler(cmd)
 
     def close(self):
         logger.warning("[%s] Closing connection", self.id())
@@ -326,10 +322,10 @@ class BaseReplicationStreamProtocol(LineOnlyReceiver):
         for cmd in pending:
             self.send_command(cmd)
 
-    def on_PING(self, line):
+    async def on_PING(self, line):
         self.received_ping = True
 
-    def on_ERROR(self, cmd):
+    async def on_ERROR(self, cmd):
         logger.error("[%s] Remote reported error: %r", self.id(), cmd.data)
 
     def pauseProducing(self):
@@ -429,16 +425,16 @@ class ServerReplicationStreamProtocol(BaseReplicationStreamProtocol):
         BaseReplicationStreamProtocol.connectionMade(self)
         self.streamer.new_connection(self)
 
-    def on_NAME(self, cmd):
+    async def on_NAME(self, cmd):
         logger.info("[%s] Renamed to %r", self.id(), cmd.data)
         self.name = cmd.data
 
-    def on_USER_SYNC(self, cmd):
-        return self.streamer.on_user_sync(
+    async def on_USER_SYNC(self, cmd):
+        await self.streamer.on_user_sync(
             self.conn_id, cmd.user_id, cmd.is_syncing, cmd.last_sync_ms
         )
 
-    def on_REPLICATE(self, cmd):
+    async def on_REPLICATE(self, cmd):
         stream_name = cmd.stream_name
         token = cmd.token
 
@@ -449,23 +445,23 @@ class ServerReplicationStreamProtocol(BaseReplicationStreamProtocol):
                 for stream in iterkeys(self.streamer.streams_by_name)
             ]
 
-            return make_deferred_yieldable(
+            await make_deferred_yieldable(
                 defer.gatherResults(deferreds, consumeErrors=True)
             )
         else:
-            return self.subscribe_to_stream(stream_name, token)
+            await self.subscribe_to_stream(stream_name, token)
 
-    def on_FEDERATION_ACK(self, cmd):
-        return self.streamer.federation_ack(cmd.token)
+    async def on_FEDERATION_ACK(self, cmd):
+        self.streamer.federation_ack(cmd.token)
 
-    def on_REMOVE_PUSHER(self, cmd):
-        return self.streamer.on_remove_pusher(cmd.app_id, cmd.push_key, cmd.user_id)
+    async def on_REMOVE_PUSHER(self, cmd):
+        await self.streamer.on_remove_pusher(cmd.app_id, cmd.push_key, cmd.user_id)
 
-    def on_INVALIDATE_CACHE(self, cmd):
-        return self.streamer.on_invalidate_cache(cmd.cache_func, cmd.keys)
+    async def on_INVALIDATE_CACHE(self, cmd):
+        self.streamer.on_invalidate_cache(cmd.cache_func, cmd.keys)
 
-    def on_USER_IP(self, cmd):
-        return self.streamer.on_user_ip(
+    async def on_USER_IP(self, cmd):
+        self.streamer.on_user_ip(
             cmd.user_id,
             cmd.access_token,
             cmd.ip,
@@ -474,8 +470,7 @@ class ServerReplicationStreamProtocol(BaseReplicationStreamProtocol):
             cmd.last_seen,
         )
 
-    @defer.inlineCallbacks
-    def subscribe_to_stream(self, stream_name, token):
+    async def subscribe_to_stream(self, stream_name, token):
         """Subscribe the remote to a stream.
 
         This invloves checking if they've missed anything and sending those
@@ -487,7 +482,7 @@ class ServerReplicationStreamProtocol(BaseReplicationStreamProtocol):
 
         try:
             # Get missing updates
-            updates, current_token = yield self.streamer.get_stream_updates(
+            updates, current_token = await self.streamer.get_stream_updates(
                 stream_name, token
             )
 
@@ -572,7 +567,7 @@ class AbstractReplicationClientHandler(metaclass=abc.ABCMeta):
     """
 
     @abc.abstractmethod
-    def on_rdata(self, stream_name, token, rows):
+    async def on_rdata(self, stream_name, token, rows):
         """Called to handle a batch of replication data with a given stream token.
 
         Args:
@@ -580,14 +575,11 @@ class AbstractReplicationClientHandler(metaclass=abc.ABCMeta):
             token (int): stream token for this batch of rows
             rows (list): a list of Stream.ROW_TYPE objects as returned by
                 Stream.parse_row.
-
-        Returns:
-            Deferred|None
         """
         raise NotImplementedError()
 
     @abc.abstractmethod
-    def on_position(self, stream_name, token):
+    async def on_position(self, stream_name, token):
         """Called when we get new position data."""
         raise NotImplementedError()
 
@@ -676,12 +668,12 @@ class ClientReplicationStreamProtocol(BaseReplicationStreamProtocol):
         if not self.streams_connecting:
             self.handler.finished_connecting()
 
-    def on_SERVER(self, cmd):
+    async def on_SERVER(self, cmd):
         if cmd.data != self.server_name:
             logger.error("[%s] Connected to wrong remote: %r", self.id(), cmd.data)
             self.send_error("Wrong remote")
 
-    def on_RDATA(self, cmd):
+    async def on_RDATA(self, cmd):
         stream_name = cmd.stream_name
         inbound_rdata_count.labels(stream_name).inc()
 
@@ -701,19 +693,19 @@ class ClientReplicationStreamProtocol(BaseReplicationStreamProtocol):
             # Check if this is the last of a batch of updates
             rows = self.pending_batches.pop(stream_name, [])
             rows.append(row)
-            return self.handler.on_rdata(stream_name, cmd.token, rows)
+            await self.handler.on_rdata(stream_name, cmd.token, rows)
 
-    def on_POSITION(self, cmd):
+    async def on_POSITION(self, cmd):
         # When we get a `POSITION` command it means we've finished getting
         # missing updates for the given stream, and are now up to date.
         self.streams_connecting.discard(cmd.stream_name)
         if not self.streams_connecting:
             self.handler.finished_connecting()
 
-        return self.handler.on_position(cmd.stream_name, cmd.token)
+        await self.handler.on_position(cmd.stream_name, cmd.token)
 
-    def on_SYNC(self, cmd):
-        return self.handler.on_sync(cmd.data)
+    async def on_SYNC(self, cmd):
+        self.handler.on_sync(cmd.data)
 
     def replicate(self, stream_name, token):
         """Send the subscription request to the server