Thread through instance name to replication client. (#7369)

For in memory streams when fetching updates on workers we need to query the source of the stream, which currently is hard coded to be master. This PR threads through the source instance we received via `POSITION` through to the update function in each stream, which can then be passed to the replication client for in memory streams.

7 files changed, 90 insertions, 29 deletions

diff --git a/synapse/replication/http/_base.py b/synapse/replication/http/_base.py
index 1be1ccbdf3..f88c80ae84 100644
--- a/synapse/replication/http/_base.py
+++ b/synapse/replication/http/_base.py
@@ -16,6 +16,7 @@
 import abc
 import logging
 import re
+from inspect import signature
 from typing import Dict, List, Tuple
 
 from six import raise_from
@@ -60,6 +61,8 @@ class ReplicationEndpoint(object):
     must call `register` to register the path with the HTTP server.
 
     Requests can be sent by calling the client returned by `make_client`.
+    Requests are sent to master process by default, but can be sent to other
+    named processes by specifying an `instance_name` keyword argument.
 
     Attributes:
         NAME (str): A name for the endpoint, added to the path as well as used
@@ -91,6 +94,16 @@ class ReplicationEndpoint(object):
                 hs, "repl." + self.NAME, timeout_ms=30 * 60 * 1000
             )
 
+        # We reserve `instance_name` as a parameter to sending requests, so we
+        # assert here that sub classes don't try and use the name.
+        assert (
+            "instance_name" not in self.PATH_ARGS
+        ), "`instance_name` is a reserved paramater name"
+        assert (
+            "instance_name"
+            not in signature(self.__class__._serialize_payload).parameters
+        ), "`instance_name` is a reserved paramater name"
+
         assert self.METHOD in ("PUT", "POST", "GET")
 
     @abc.abstractmethod
@@ -135,7 +148,11 @@ class ReplicationEndpoint(object):
 
         @trace(opname="outgoing_replication_request")
         @defer.inlineCallbacks
-        def send_request(**kwargs):
+        def send_request(instance_name="master", **kwargs):
+            # Currently we only support sending requests to master process.
+            if instance_name != "master":
+                raise Exception("Unknown instance")
+
             data = yield cls._serialize_payload(**kwargs)
 
             url_args = [
diff --git a/synapse/replication/http/streams.py b/synapse/replication/http/streams.py
index f35cebc710..0459f582bf 100644
--- a/synapse/replication/http/streams.py
+++ b/synapse/replication/http/streams.py
@@ -50,6 +50,8 @@ class ReplicationGetStreamUpdates(ReplicationEndpoint):
     def __init__(self, hs):
         super().__init__(hs)
 
+        self._instance_name = hs.get_instance_name()
+
         # We pull the streams from the replication steamer (if we try and make
         # them ourselves we end up in an import loop).
         self.streams = hs.get_replication_streamer().get_streams()
@@ -67,7 +69,7 @@ class ReplicationGetStreamUpdates(ReplicationEndpoint):
         upto_token = parse_integer(request, "upto_token", required=True)
 
         updates, upto_token, limited = await stream.get_updates_since(
-            from_token, upto_token
+            self._instance_name, from_token, upto_token
         )
 
         return (
diff --git a/synapse/replication/tcp/client.py b/synapse/replication/tcp/client.py
index 5c28fd4ac3..3bbf3c3569 100644
--- a/synapse/replication/tcp/client.py
+++ b/synapse/replication/tcp/client.py
@@ -86,17 +86,19 @@ class ReplicationDataHandler:
     def __init__(self, store: BaseSlavedStore):
         self.store = store
 
-    async def on_rdata(self, stream_name: str, token: int, rows: list):
+    async def on_rdata(
+        self, stream_name: str, instance_name: str, token: int, rows: list
+    ):
         """Called to handle a batch of replication data with a given stream token.
 
         By default this just pokes the slave store. Can be overridden in subclasses to
         handle more.
 
         Args:
-            stream_name (str): name of the replication stream for this batch of rows
-            token (int): stream token for this batch of rows
-            rows (list): a list of Stream.ROW_TYPE objects as returned by
-                Stream.parse_row.
+            stream_name: name of the replication stream for this batch of rows
+            instance_name: the instance that wrote the rows.
+            token: stream token for this batch of rows
+            rows: a list of Stream.ROW_TYPE objects as returned by Stream.parse_row.
         """
         self.store.process_replication_rows(stream_name, token, rows)
 
diff --git a/synapse/replication/tcp/handler.py b/synapse/replication/tcp/handler.py
index d72f3d0cf9..2d1d119c7c 100644
--- a/synapse/replication/tcp/handler.py
+++ b/synapse/replication/tcp/handler.py
@@ -278,19 +278,24 @@ class ReplicationCommandHandler:
                 # Check if this is the last of a batch of updates
                 rows = self._pending_batches.pop(stream_name, [])
                 rows.append(row)
-                await self.on_rdata(stream_name, cmd.token, rows)
+                await self.on_rdata(stream_name, cmd.instance_name, cmd.token, rows)
 
-    async def on_rdata(self, stream_name: str, token: int, rows: list):
+    async def on_rdata(
+        self, stream_name: str, instance_name: str, token: int, rows: list
+    ):
         """Called to handle a batch of replication data with a given stream token.
 
         Args:
             stream_name: name of the replication stream for this batch of rows
+            instance_name: the instance that wrote the rows.
             token: stream token for this batch of rows
             rows: a list of Stream.ROW_TYPE objects as returned by
                 Stream.parse_row.
         """
         logger.debug("Received rdata %s -> %s", stream_name, token)
-        await self._replication_data_handler.on_rdata(stream_name, token, rows)
+        await self._replication_data_handler.on_rdata(
+            stream_name, instance_name, token, rows
+        )
 
     async def on_POSITION(self, conn: AbstractConnection, cmd: PositionCommand):
         if cmd.instance_name == self._instance_name:
@@ -325,7 +330,9 @@ class ReplicationCommandHandler:
                     updates,
                     current_token,
                     missing_updates,
-                ) = await stream.get_updates_since(current_token, cmd.token)
+                ) = await stream.get_updates_since(
+                    cmd.instance_name, current_token, cmd.token
+                )
 
                 # TODO: add some tests for this
 
@@ -334,7 +341,10 @@ class ReplicationCommandHandler:
 
                 for token, rows in _batch_updates(updates):
                     await self.on_rdata(
-                        cmd.stream_name, token, [stream.parse_row(row) for row in rows],
+                        cmd.stream_name,
+                        cmd.instance_name,
+                        token,
+                        [stream.parse_row(row) for row in rows],
                     )
 
             # We've now caught up to position sent to us, notify handler.
diff --git a/synapse/replication/tcp/streams/_base.py b/synapse/replication/tcp/streams/_base.py
index 4af1afd119..b0f87c365b 100644
--- a/synapse/replication/tcp/streams/_base.py
+++ b/synapse/replication/tcp/streams/_base.py
@@ -16,7 +16,7 @@
 
 import logging
 from collections import namedtuple
-from typing import Any, Awaitable, Callable, Iterable, List, Optional, Tuple
+from typing import Any, Awaitable, Callable, List, Optional, Tuple
 
 import attr
 
@@ -53,6 +53,7 @@ StreamUpdateResult = Tuple[List[Tuple[Token, StreamRow]], Token, bool]
 #
 # The arguments are:
 #
+#  * instance_name: the writer of the stream
 #  * from_token: the previous stream token: the starting point for fetching the
 #    updates
 #  * to_token: the new stream token: the point to get updates up to
@@ -62,7 +63,7 @@ StreamUpdateResult = Tuple[List[Tuple[Token, StreamRow]], Token, bool]
 # If there are more updates available, it should set `limited` in the result, and
 # it will be called again to get the next batch.
 #
-UpdateFunction = Callable[[Token, Token, int], Awaitable[StreamUpdateResult]]
+UpdateFunction = Callable[[str, Token, Token, int], Awaitable[StreamUpdateResult]]
 
 
 class Stream(object):
@@ -93,6 +94,7 @@ class Stream(object):
 
     def __init__(
         self,
+        local_instance_name: str,
         current_token_function: Callable[[], Token],
         update_function: UpdateFunction,
     ):
@@ -108,9 +110,11 @@ class Stream(object):
         stream tokens. See the UpdateFunction type definition for more info.
 
         Args:
+            local_instance_name: The instance name of the current process
             current_token_function: callback to get the current token, as above
             update_function: callback go get stream updates, as above
         """
+        self.local_instance_name = local_instance_name
         self.current_token = current_token_function
         self.update_function = update_function
 
@@ -135,14 +139,14 @@ class Stream(object):
         """
         current_token = self.current_token()
         updates, current_token, limited = await self.get_updates_since(
-            self.last_token, current_token
+            self.local_instance_name, self.last_token, current_token
         )
         self.last_token = current_token
 
         return updates, current_token, limited
 
     async def get_updates_since(
-        self, from_token: Token, upto_token: Token
+        self, instance_name: str, from_token: Token, upto_token: Token
     ) -> StreamUpdateResult:
         """Like get_updates except allows specifying from when we should
         stream updates
@@ -160,19 +164,19 @@ class Stream(object):
             return [], upto_token, False
 
         updates, upto_token, limited = await self.update_function(
-            from_token, upto_token, _STREAM_UPDATE_TARGET_ROW_COUNT,
+            instance_name, from_token, upto_token, _STREAM_UPDATE_TARGET_ROW_COUNT,
         )
         return updates, upto_token, limited
 
 
 def db_query_to_update_function(
-    query_function: Callable[[Token, Token, int], Awaitable[Iterable[tuple]]]
+    query_function: Callable[[Token, Token, int], Awaitable[List[tuple]]]
 ) -> UpdateFunction:
     """Wraps a db query function which returns a list of rows to make it
     suitable for use as an `update_function` for the Stream class
     """
 
-    async def update_function(from_token, upto_token, limit):
+    async def update_function(instance_name, from_token, upto_token, limit):
         rows = await query_function(from_token, upto_token, limit)
         updates = [(row[0], row[1:]) for row in rows]
         limited = False
@@ -193,10 +197,13 @@ def make_http_update_function(hs, stream_name: str) -> UpdateFunction:
     client = ReplicationGetStreamUpdates.make_client(hs)
 
     async def update_function(
-        from_token: int, upto_token: int, limit: int
+        instance_name: str, from_token: int, upto_token: int, limit: int
     ) -> StreamUpdateResult:
         result = await client(
-            stream_name=stream_name, from_token=from_token, upto_token=upto_token,
+            instance_name=instance_name,
+            stream_name=stream_name,
+            from_token=from_token,
+            upto_token=upto_token,
         )
         return result["updates"], result["upto_token"], result["limited"]
 
@@ -226,6 +233,7 @@ class BackfillStream(Stream):
     def __init__(self, hs):
         store = hs.get_datastore()
         super().__init__(
+            hs.get_instance_name(),
             store.get_current_backfill_token,
             db_query_to_update_function(store.get_all_new_backfill_event_rows),
         )
@@ -261,7 +269,9 @@ class PresenceStream(Stream):
             # Query master process
             update_function = make_http_update_function(hs, self.NAME)
 
-        super().__init__(store.get_current_presence_token, update_function)
+        super().__init__(
+            hs.get_instance_name(), store.get_current_presence_token, update_function
+        )
 
 
 class TypingStream(Stream):
@@ -284,7 +294,9 @@ class TypingStream(Stream):
             # Query master process
             update_function = make_http_update_function(hs, self.NAME)
 
-        super().__init__(typing_handler.get_current_token, update_function)
+        super().__init__(
+            hs.get_instance_name(), typing_handler.get_current_token, update_function
+        )
 
 
 class ReceiptsStream(Stream):
@@ -305,6 +317,7 @@ class ReceiptsStream(Stream):
     def __init__(self, hs):
         store = hs.get_datastore()
         super().__init__(
+            hs.get_instance_name(),
             store.get_max_receipt_stream_id,
             db_query_to_update_function(store.get_all_updated_receipts),
         )
@@ -322,14 +335,16 @@ class PushRulesStream(Stream):
     def __init__(self, hs):
         self.store = hs.get_datastore()
         super(PushRulesStream, self).__init__(
-            self._current_token, self._update_function
+            hs.get_instance_name(), self._current_token, self._update_function
         )
 
     def _current_token(self) -> int:
         push_rules_token, _ = self.store.get_push_rules_stream_token()
         return push_rules_token
 
-    async def _update_function(self, from_token: Token, to_token: Token, limit: int):
+    async def _update_function(
+        self, instance_name: str, from_token: Token, to_token: Token, limit: int
+    ):
         rows = await self.store.get_all_push_rule_updates(from_token, to_token, limit)
 
         limited = False
@@ -356,6 +371,7 @@ class PushersStream(Stream):
         store = hs.get_datastore()
 
         super().__init__(
+            hs.get_instance_name(),
             store.get_pushers_stream_token,
             db_query_to_update_function(store.get_all_updated_pushers_rows),
         )
@@ -387,6 +403,7 @@ class CachesStream(Stream):
     def __init__(self, hs):
         store = hs.get_datastore()
         super().__init__(
+            hs.get_instance_name(),
             store.get_cache_stream_token,
             db_query_to_update_function(store.get_all_updated_caches),
         )
@@ -412,6 +429,7 @@ class PublicRoomsStream(Stream):
     def __init__(self, hs):
         store = hs.get_datastore()
         super().__init__(
+            hs.get_instance_name(),
             store.get_current_public_room_stream_id,
             db_query_to_update_function(store.get_all_new_public_rooms),
         )
@@ -432,6 +450,7 @@ class DeviceListsStream(Stream):
     def __init__(self, hs):
         store = hs.get_datastore()
         super().__init__(
+            hs.get_instance_name(),
             store.get_device_stream_token,
             db_query_to_update_function(store.get_all_device_list_changes_for_remotes),
         )
@@ -449,6 +468,7 @@ class ToDeviceStream(Stream):
     def __init__(self, hs):
         store = hs.get_datastore()
         super().__init__(
+            hs.get_instance_name(),
             store.get_to_device_stream_token,
             db_query_to_update_function(store.get_all_new_device_messages),
         )
@@ -468,6 +488,7 @@ class TagAccountDataStream(Stream):
     def __init__(self, hs):
         store = hs.get_datastore()
         super().__init__(
+            hs.get_instance_name(),
             store.get_max_account_data_stream_id,
             db_query_to_update_function(store.get_all_updated_tags),
         )
@@ -487,6 +508,7 @@ class AccountDataStream(Stream):
     def __init__(self, hs):
         self.store = hs.get_datastore()
         super().__init__(
+            hs.get_instance_name(),
             self.store.get_max_account_data_stream_id,
             db_query_to_update_function(self._update_function),
         )
@@ -517,6 +539,7 @@ class GroupServerStream(Stream):
     def __init__(self, hs):
         store = hs.get_datastore()
         super().__init__(
+            hs.get_instance_name(),
             store.get_group_stream_token,
             db_query_to_update_function(store.get_all_groups_changes),
         )
@@ -534,6 +557,7 @@ class UserSignatureStream(Stream):
     def __init__(self, hs):
         store = hs.get_datastore()
         super().__init__(
+            hs.get_instance_name(),
             store.get_device_stream_token,
             db_query_to_update_function(
                 store.get_all_user_signature_changes_for_remotes
diff --git a/synapse/replication/tcp/streams/events.py b/synapse/replication/tcp/streams/events.py
index 52df81b1bd..890e75d827 100644
--- a/synapse/replication/tcp/streams/events.py
+++ b/synapse/replication/tcp/streams/events.py
@@ -118,11 +118,17 @@ class EventsStream(Stream):
     def __init__(self, hs):
         self._store = hs.get_datastore()
         super().__init__(
-            self._store.get_current_events_token, self._update_function,
+            hs.get_instance_name(),
+            self._store.get_current_events_token,
+            self._update_function,
         )
 
     async def _update_function(
-        self, from_token: Token, current_token: Token, target_row_count: int
+        self,
+        instance_name: str,
+        from_token: Token,
+        current_token: Token,
+        target_row_count: int,
     ) -> StreamUpdateResult:
 
         # the events stream merges together three separate sources:
diff --git a/synapse/replication/tcp/streams/federation.py b/synapse/replication/tcp/streams/federation.py
index 75133d7e40..e8bd52e389 100644
--- a/synapse/replication/tcp/streams/federation.py
+++ b/synapse/replication/tcp/streams/federation.py
@@ -48,8 +48,8 @@ class FederationStream(Stream):
             current_token = lambda: 0
             update_function = self._stub_update_function
 
-        super().__init__(current_token, update_function)
+        super().__init__(hs.get_instance_name(), current_token, update_function)
 
     @staticmethod
-    async def _stub_update_function(from_token, upto_token, limit):
+    async def _stub_update_function(instance_name, from_token, upto_token, limit):
         return [], upto_token, False