Move server command handling out of TCP protocol (#7187)

This completes the merging of server and client command processing.

changelog.d/7187.misc

@@ -0,0 +1 @@
+Move server command handling out of TCP protocol.

synapse/replication/tcp/handler.py

@@ -19,19 +19,23 @@
 
 from prometheus_client import Counter
 
+from synapse.metrics import LaterGauge
 from synapse.replication.tcp.client import ReplicationClientFactory
 from synapse.replication.tcp.commands import (
+    ClearUserSyncsCommand,
     Command,
     FederationAckCommand,
     InvalidateCacheCommand,
     PositionCommand,
     RdataCommand,
     RemoteServerUpCommand,
     RemovePusherCommand,
+    ReplicateCommand,
     SyncCommand,
     UserIpCommand,
     UserSyncCommand,
 )
+from synapse.replication.tcp.protocol import AbstractConnection
 from synapse.replication.tcp.streams import STREAMS_MAP, Stream
 from synapse.util.async_helpers import Linearizer
 
@@ -42,6 +46,13 @@
 inbound_rdata_count = Counter(
     "synapse_replication_tcp_protocol_inbound_rdata_count", "", ["stream_name"]
 )
+user_sync_counter = Counter("synapse_replication_tcp_resource_user_sync", "")
+federation_ack_counter = Counter("synapse_replication_tcp_resource_federation_ack", "")
+remove_pusher_counter = Counter("synapse_replication_tcp_resource_remove_pusher", "")
+invalidate_cache_counter = Counter(
+    "synapse_replication_tcp_resource_invalidate_cache", ""
+)
+user_ip_cache_counter = Counter("synapse_replication_tcp_resource_user_ip_cache", "")
 
 
 class ReplicationCommandHandler:
@@ -52,6 +63,10 @@ class ReplicationCommandHandler:
     def __init__(self, hs):
         self._replication_data_handler = hs.get_replication_data_handler()
         self._presence_handler = hs.get_presence_handler()
+        self._store = hs.get_datastore()
+        self._notifier = hs.get_notifier()
+        self._clock = hs.get_clock()
+        self._instance_id = hs.get_instance_id()
 
         # Set of streams that we've caught up with.
         self._streams_connected = set()  # type: Set[str]
@@ -69,8 +84,26 @@ def __init__(self, hs):
         # The factory used to create connections.
         self._factory = None  # type: Optional[ReplicationClientFactory]
 
-        # The current connection. None if we are currently (re)connecting
-        self._connection = None
+        # The currently connected connections.
+        self._connections = []  # type: List[AbstractConnection]
+
+        LaterGauge(
+            "synapse_replication_tcp_resource_total_connections",
+            "",
+            [],
+            lambda: len(self._connections),
+        )
+
+        self._is_master = hs.config.worker_app is None
+
+        self._federation_sender = None
+        if self._is_master and not hs.config.send_federation:
+            self._federation_sender = hs.get_federation_sender()
+
+        self._server_notices_sender = None
+        if self._is_master:
+            self._server_notices_sender = hs.get_server_notices_sender()
+            self._notifier.add_remote_server_up_callback(self.send_remote_server_up)
 
     def start_replication(self, hs):
         """Helper method to start a replication connection to the remote server
@@ -82,6 +115,70 @@ def start_replication(self, hs):
         port = hs.config.worker_replication_port
         hs.get_reactor().connectTCP(host, port, self._factory)
 
+    async def on_REPLICATE(self, cmd: ReplicateCommand):
+        # We only want to announce positions by the writer of the streams.
+        # Currently this is just the master process.
+        if not self._is_master:
+            return
+
+        for stream_name, stream in self._streams.items():
+            current_token = stream.current_token()
+            self.send_command(PositionCommand(stream_name, current_token))
+
+    async def on_USER_SYNC(self, cmd: UserSyncCommand):
+        user_sync_counter.inc()
+
+        if self._is_master:
+            await self._presence_handler.update_external_syncs_row(
+                cmd.instance_id, cmd.user_id, cmd.is_syncing, cmd.last_sync_ms
+            )
+
+    async def on_CLEAR_USER_SYNC(self, cmd: ClearUserSyncsCommand):
+        if self._is_master:
+            await self._presence_handler.update_external_syncs_clear(cmd.instance_id)
+
+    async def on_FEDERATION_ACK(self, cmd: FederationAckCommand):
+        federation_ack_counter.inc()
+
+        if self._federation_sender:
+            self._federation_sender.federation_ack(cmd.token)
+
+    async def on_REMOVE_PUSHER(self, cmd: RemovePusherCommand):
+        remove_pusher_counter.inc()
+
+        if self._is_master:
+            await self._store.delete_pusher_by_app_id_pushkey_user_id(
+                app_id=cmd.app_id, pushkey=cmd.push_key, user_id=cmd.user_id
+            )
+
+            self._notifier.on_new_replication_data()
+
+    async def on_INVALIDATE_CACHE(self, cmd: InvalidateCacheCommand):
+        invalidate_cache_counter.inc()
+
+        if self._is_master:
+            # We invalidate the cache locally, but then also stream that to other
+            # workers.
+            await self._store.invalidate_cache_and_stream(
+                cmd.cache_func, tuple(cmd.keys)
+            )
+
+    async def on_USER_IP(self, cmd: UserIpCommand):
+        user_ip_cache_counter.inc()
+
+        if self._is_master:
+            await self._store.insert_client_ip(
+                cmd.user_id,
+                cmd.access_token,
+                cmd.ip,
+                cmd.user_agent,
+                cmd.device_id,
+                cmd.last_seen,
+            )
+
+        if self._server_notices_sender:
+            await self._server_notices_sender.on_user_ip(cmd.user_id)
+
     async def on_RDATA(self, cmd: RdataCommand):
         stream_name = cmd.stream_name
         inbound_rdata_count.labels(stream_name).inc()
@@ -174,36 +271,73 @@ async def on_REMOTE_SERVER_UP(self, cmd: RemoteServerUpCommand):
         """"Called when get a new REMOTE_SERVER_UP command."""
         self._replication_data_handler.on_remote_server_up(cmd.data)
 
+        if self._is_master:
+            self._notifier.notify_remote_server_up(cmd.data)
+
     def get_currently_syncing_users(self):
         """Get the list of currently syncing users (if any). This is called
         when a connection has been established and we need to send the
         currently syncing users.
         """
         return self._presence_handler.get_currently_syncing_users()
 
-    def update_connection(self, connection):
-        """Called when a connection has been established (or lost with None).
+    def new_connection(self, connection: AbstractConnection):
+        """Called when we have a new connection.
         """
-        self._connection = connection
+        self._connections.append(connection)
+
+        # If we are connected to replication as a client (rather than a server)
+        # we need to reset the reconnection delay on the client factory (which
+        # is used to do exponential back off when the connection drops).
+        #
+        # Ideally we would reset the delay when we've "fully established" the
+        # connection (for some definition thereof) to stop us from tightlooping
+        # on reconnection if something fails after this point and we drop the
+        # connection. Unfortunately, we don't really have a better definition of
+        # "fully established" than the connection being established.
+        if self._factory:
+            self._factory.resetDelay()
+
+        # Tell the server if we have any users currently syncing (should only
+        # happen on synchrotrons)
+        currently_syncing = self.get_currently_syncing_users()
+        now = self._clock.time_msec()
+        for user_id in currently_syncing:
+            connection.send_command(
+                UserSyncCommand(self._instance_id, user_id, True, now)
+            )
 
-    def finished_connecting(self):
-        """Called when we have successfully subscribed and caught up to all
-        streams we're interested in.
+    def lost_connection(self, connection: AbstractConnection):
+        """Called when a connection is closed/lost.
         """
-        logger.info("Finished connecting to server")
+        try:
+            self._connections.remove(connection)
+        except ValueError:
+            pass
 
-        # We don't reset the delay any earlier as otherwise if there is a
-        # problem during start up we'll end up tight looping connecting to the
-        # server.
-        if self._factory:
-            self._factory.resetDelay()
+    def connected(self) -> bool:
+        """Do we have any replication connections open?
+
+        Is used by e.g. `ReplicationStreamer` to no-op if nothing is connected.
+        """
+        return bool(self._connections)
 
     def send_command(self, cmd: Command):
-        """Send a command to master (when we get establish a connection if we
-        don't have one already.)
+        """Send a command to all connected connections.
         """
-        if self._connection:
-            self._connection.send_command(cmd)
+        if self._connections:
+            for connection in self._connections:
+                try:
+                    connection.send_command(cmd)
+                except Exception:
+                    # We probably want to catch some types of exceptions here
+                    # and log them as warnings (e.g. connection gone), but I
+                    # can't find what those exception types they would be.
+                    logger.exception(
+                        "Failed to write command %s to connection %s",
+                        cmd.NAME,
+                        connection,
+                    )
         else:
             logger.warning("Dropping command as not connected: %r", cmd.NAME)
 
@@ -250,3 +384,10 @@ def send_user_ip(
 
     def send_remote_server_up(self, server: str):
         self.send_command(RemoteServerUpCommand(server))
+
+    def stream_update(self, stream_name: str, token: str, data: Any):
+        """Called when a new update is available to stream to clients.
+
+        We need to check if the client is interested in the stream or not
+        """
+        self.send_command(RdataCommand(stream_name, token, data))