Add instance name to RDATA/POSITION commands (#7364)

This is primarily for allowing us to send those commands from workers, but for now simply allows us to ignore echoed RDATA/POSITION commands that we sent (we get echoes of sent commands when using redis). Currently we log a WARNING on the master process every time we receive an echoed RDATA.

2 files changed, 40 insertions, 14 deletions

diff --git a/synapse/replication/tcp/commands.py b/synapse/replication/tcp/commands.py
index c7880d4b63..f58e384d17 100644
--- a/synapse/replication/tcp/commands.py
+++ b/synapse/replication/tcp/commands.py
@@ -95,7 +95,7 @@ class RdataCommand(Command):
 
     Format::
 
-        RDATA <stream_name> <token> <row_json>
+        RDATA <stream_name> <instance_name> <token> <row_json>
 
     The `<token>` may either be a numeric stream id OR "batch". The latter case
     is used to support sending multiple updates with the same stream ID. This
@@ -105,33 +105,40 @@ class RdataCommand(Command):
     The client should batch all incoming RDATA with a token of "batch" (per
     stream_name) until it sees an RDATA with a numeric stream ID.
 
+    The `<instance_name>` is the source of the new data (usually "master").
+
     `<token>` of "batch" maps to the instance variable `token` being None.
 
     An example of a batched series of RDATA::
 
-        RDATA presence batch ["@foo:example.com", "online", ...]
-        RDATA presence batch ["@bar:example.com", "online", ...]
-        RDATA presence 59 ["@baz:example.com", "online", ...]
+        RDATA presence master batch ["@foo:example.com", "online", ...]
+        RDATA presence master batch ["@bar:example.com", "online", ...]
+        RDATA presence master 59 ["@baz:example.com", "online", ...]
     """
 
     NAME = "RDATA"
 
-    def __init__(self, stream_name, token, row):
+    def __init__(self, stream_name, instance_name, token, row):
         self.stream_name = stream_name
+        self.instance_name = instance_name
         self.token = token
         self.row = row
 
     @classmethod
     def from_line(cls, line):
-        stream_name, token, row_json = line.split(" ", 2)
+        stream_name, instance_name, token, row_json = line.split(" ", 3)
         return cls(
-            stream_name, None if token == "batch" else int(token), json.loads(row_json)
+            stream_name,
+            instance_name,
+            None if token == "batch" else int(token),
+            json.loads(row_json),
         )
 
     def to_line(self):
         return " ".join(
             (
                 self.stream_name,
+                self.instance_name,
                 str(self.token) if self.token is not None else "batch",
                 _json_encoder.encode(self.row),
             )
@@ -145,23 +152,31 @@ class PositionCommand(Command):
     """Sent by the server to tell the client the stream postition without
     needing to send an RDATA.
 
+    Format::
+
+        POSITION <stream_name> <instance_name> <token>
+
     On receipt of a POSITION command clients should check if they have missed
     any updates, and if so then fetch them out of band.
+
+    The `<instance_name>` is the process that sent the command and is the source
+    of the stream.
     """
 
     NAME = "POSITION"
 
-    def __init__(self, stream_name, token):
+    def __init__(self, stream_name, instance_name, token):
         self.stream_name = stream_name
+        self.instance_name = instance_name
         self.token = token
 
     @classmethod
     def from_line(cls, line):
-        stream_name, token = line.split(" ", 1)
-        return cls(stream_name, int(token))
+        stream_name, instance_name, token = line.split(" ", 2)
+        return cls(stream_name, instance_name, int(token))
 
     def to_line(self):
-        return " ".join((self.stream_name, str(self.token)))
+        return " ".join((self.stream_name, self.instance_name, str(self.token)))
 
 
 class ErrorCommand(_SimpleCommand):
diff --git a/synapse/replication/tcp/handler.py b/synapse/replication/tcp/handler.py
index b8f49a8d0f..6f7054d5af 100644
--- a/synapse/replication/tcp/handler.py
+++ b/synapse/replication/tcp/handler.py
@@ -79,6 +79,7 @@ class ReplicationCommandHandler:
         self._notifier = hs.get_notifier()
         self._clock = hs.get_clock()
         self._instance_id = hs.get_instance_id()
+        self._instance_name = hs.get_instance_name()
 
         # Set of streams that we've caught up with.
         self._streams_connected = set()  # type: Set[str]
@@ -156,7 +157,7 @@ class ReplicationCommandHandler:
                 hs.config.redis.redis_host, hs.config.redis.redis_port, self._factory,
             )
         else:
-            client_name = hs.config.worker_name
+            client_name = hs.get_instance_name()
             self._factory = DirectTcpReplicationClientFactory(hs, client_name, self)
             host = hs.config.worker_replication_host
             port = hs.config.worker_replication_port
@@ -170,7 +171,9 @@ class ReplicationCommandHandler:
 
         for stream_name, stream in self._streams.items():
             current_token = stream.current_token()
-            self.send_command(PositionCommand(stream_name, current_token))
+            self.send_command(
+                PositionCommand(stream_name, self._instance_name, current_token)
+            )
 
     async def on_USER_SYNC(self, conn: AbstractConnection, cmd: UserSyncCommand):
         user_sync_counter.inc()
@@ -235,6 +238,10 @@ class ReplicationCommandHandler:
             await self._server_notices_sender.on_user_ip(cmd.user_id)
 
     async def on_RDATA(self, conn: AbstractConnection, cmd: RdataCommand):
+        if cmd.instance_name == self._instance_name:
+            # Ignore RDATA that are just our own echoes
+            return
+
         stream_name = cmd.stream_name
         inbound_rdata_count.labels(stream_name).inc()
 
@@ -286,6 +293,10 @@ class ReplicationCommandHandler:
         await self._replication_data_handler.on_rdata(stream_name, token, rows)
 
     async def on_POSITION(self, conn: AbstractConnection, cmd: PositionCommand):
+        if cmd.instance_name == self._instance_name:
+            # Ignore POSITION that are just our own echoes
+            return
+
         stream = self._streams.get(cmd.stream_name)
         if not stream:
             logger.error("Got POSITION for unknown stream: %s", cmd.stream_name)
@@ -485,7 +496,7 @@ class ReplicationCommandHandler:
 
         We need to check if the client is interested in the stream or not
         """
-        self.send_command(RdataCommand(stream_name, token, data))
+        self.send_command(RdataCommand(stream_name, self._instance_name, token, data))
 
 
 UpdateToken = TypeVar("UpdateToken")