Separate `get_current_token` into two. (#8113)

The function is used for two purposes: 1) for subscribers of streams to
get a token they can use to get further updates with, and 2) for
replication to track position of the writers of the stream.

For streams with a single writer the two scenarios produce the same
result, however the situation becomes complicated for streams with
multiple writers. The current `MultiWriterIdGenerator` does not
correctly handle the first case (which is not an issue as its only used
for the `caches` stream which nothing subscribes to outside of
replication).

1 files changed, 2 insertions, 2 deletions

diff --git a/synapse/storage/databases/main/cache.py b/synapse/storage/databases/main/cache.py
index 10de446065..1e7637a6f5 100644
--- a/synapse/storage/databases/main/cache.py
+++ b/synapse/storage/databases/main/cache.py
@@ -299,8 +299,8 @@ class CacheInvalidationWorkerStore(SQLBaseStore):
                 },
             )
 
-    def get_cache_stream_token(self, instance_name):
+    def get_cache_stream_token_for_writer(self, instance_name: str) -> int:
         if self._cache_id_gen:
-            return self._cache_id_gen.get_current_token(instance_name)
+            return self._cache_id_gen.get_current_token_for_writer(instance_name)
         else:
             return 0