Implement cache replication stream

synapse/replication/slave/storage/_base.py

@@ -14,15 +14,43 @@
 # limitations under the License.
 
 from synapse.storage._base import SQLBaseStore
+from synapse.storage.engines import PostgresEngine
 from twisted.internet import defer
 
+from ._slaved_id_tracker import SlavedIdTracker
+
+import logging
+
+logger = logging.getLogger(__name__)
+
 
 class BaseSlavedStore(SQLBaseStore):
     def __init__(self, db_conn, hs):
         super(BaseSlavedStore, self).__init__(hs)
+        if isinstance(self.database_engine, PostgresEngine):
+            self._cache_id_gen = SlavedIdTracker(
+                db_conn, "cache_stream", "stream_id",
+            )
+        else:
+            self._cache_id_gen = None
 
     def stream_positions(self):
-        return {}
+        pos = {}
+        if self._cache_id_gen:
+            pos["caches"] = self._cache_id_gen.get_current_token()
+        return pos
 
     def process_replication(self, result):
+        stream = result.get("caches")
+        if stream:
+            for row in stream["rows"]:
+                (
+                    position, cache_func, keys, invalidation_ts,
+                ) = row
+
+                try:
+                    getattr(self, cache_func).invalidate(tuple(keys))
+                except AttributeError:
+                    logger.warn("Got unexpected cache_func: %r", cache_func)
+            self._cache_id_gen.advance(int(stream["position"]))
         return defer.succeed(None)