Convert internal pusher dicts to attrs classes. (#8940)

This improves type hinting and should use less memory.

synapse/replication/slave/storage/_slaved_id_tracker.py

@@ -12,21 +12,31 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+from typing import List, Optional, Tuple
 
+from synapse.storage.types import Connection
 from synapse.storage.util.id_generators import _load_current_id
 
 
 class SlavedIdTracker:
-    def __init__(self, db_conn, table, column, extra_tables=[], step=1):
+    def __init__(
+        self,
+        db_conn: Connection,
+        table: str,
+        column: str,
+        extra_tables: Optional[List[Tuple[str, str]]] = None,
+        step: int = 1,
+    ):
         self.step = step
         self._current = _load_current_id(db_conn, table, column, step)
-        for table, column in extra_tables:
-            self.advance(None, _load_current_id(db_conn, table, column))
+        if extra_tables:
+            for table, column in extra_tables:
+                self.advance(None, _load_current_id(db_conn, table, column))
 
-    def advance(self, instance_name, new_id):
+    def advance(self, instance_name: Optional[str], new_id: int):
         self._current = (max if self.step > 0 else min)(self._current, new_id)
 
-    def get_current_token(self):
+    def get_current_token(self) -> int:
         """
 
         Returns:

synapse/replication/slave/storage/pushers.py

@@ -13,26 +13,33 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+from typing import TYPE_CHECKING
 
 from synapse.replication.tcp.streams import PushersStream
 from synapse.storage.database import DatabasePool
 from synapse.storage.databases.main.pusher import PusherWorkerStore
+from synapse.storage.types import Connection
 
 from ._base import BaseSlavedStore
 from ._slaved_id_tracker import SlavedIdTracker
 
+if TYPE_CHECKING:
+    from synapse.app.homeserver import HomeServer
+
 
 class SlavedPusherStore(PusherWorkerStore, BaseSlavedStore):
-    def __init__(self, database: DatabasePool, db_conn, hs):
+    def __init__(self, database: DatabasePool, db_conn: Connection, hs: "HomeServer"):
         super().__init__(database, db_conn, hs)
-        self._pushers_id_gen = SlavedIdTracker(
+        self._pushers_id_gen = SlavedIdTracker(  # type: ignore
             db_conn, "pushers", "id", extra_tables=[("deleted_pushers", "stream_id")]
         )
 
-    def get_pushers_stream_token(self):
+    def get_pushers_stream_token(self) -> int:
         return self._pushers_id_gen.get_current_token()
 
-    def process_replication_rows(self, stream_name, instance_name, token, rows):
+    def process_replication_rows(
+        self, stream_name: str, instance_name: str, token, rows
+    ) -> None:
         if stream_name == PushersStream.NAME:
-            self._pushers_id_gen.advance(instance_name, token)
+            self._pushers_id_gen.advance(instance_name, token)  # type: ignore
         return super().process_replication_rows(stream_name, instance_name, token, rows)