Allow streaming cache invalidate all to workers. (#6749)

changelog.d/6749.misc

@@ -0,0 +1 @@
+Allow streaming cache 'invalidate all' to workers.

docs/tcp_replication.md

@@ -254,6 +254,11 @@ and they key to invalidate. For example:
 
     > RDATA caches 550953771 ["get_user_by_id", ["@bob:example.com"], 1550574873251]
 
+Alternatively, an entire cache can be invalidated by sending down a `null`
+instead of the key. For example:
+
+    > RDATA caches 550953772 ["get_user_by_id", null, 1550574873252]
+
 However, there are times when a number of caches need to be invalidated
 at the same time with the same key. To reduce traffic we batch those
 invalidations into a single poke by defining a special cache name that

synapse/replication/slave/storage/_base.py

@@ -66,11 +66,16 @@ def process_replication_rows(self, stream_name, token, rows):
                 self._cache_id_gen.advance(token)
             for row in rows:
                 if row.cache_func == CURRENT_STATE_CACHE_NAME:
+                    if row.keys is None:
+                        raise Exception(
+                            "Can't send an 'invalidate all' for current state cache"
+                        )
+
                     room_id = row.keys[0]
                     members_changed = set(row.keys[1:])
                     self._invalidate_state_caches(room_id, members_changed)
                 else:
-                    self._attempt_to_invalidate_cache(row.cache_func, tuple(row.keys))
+                    self._attempt_to_invalidate_cache(row.cache_func, row.keys)
 
     def _invalidate_cache_and_stream(self, txn, cache_func, keys):
         txn.call_after(cache_func.invalidate, keys)

synapse/replication/tcp/streams/_base.py

@@ -17,7 +17,9 @@
 import itertools
 import logging
 from collections import namedtuple
-from typing import Any
+from typing import Any, List, Optional
+
+import attr
 
 logger = logging.getLogger(__name__)
 
@@ -65,10 +67,24 @@
     "PushersStreamRow",
     ("user_id", "app_id", "pushkey", "deleted"),  # str  # str  # str  # bool
 )
-CachesStreamRow = namedtuple(
-    "CachesStreamRow",
-    ("cache_func", "keys", "invalidation_ts"),  # str  # list(str)  # int
-)
+
+
+@attr.s
+class CachesStreamRow:
+    """Stream to inform workers they should invalidate their cache.
+
+    Attributes:
+        cache_func: Name of the cached function.
+        keys: The entry in the cache to invalidate. If None then will
+            invalidate all.
+        invalidation_ts: Timestamp of when the invalidation took place.
+    """
+
+    cache_func = attr.ib(type=str)
+    keys = attr.ib(type=Optional[List[Any]])
+    invalidation_ts = attr.ib(type=int)
+
+
 PublicRoomsStreamRow = namedtuple(
     "PublicRoomsStreamRow",
     (

synapse/storage/_base.py

@@ -17,6 +17,7 @@
 import logging
 import random
 from abc import ABCMeta
+from typing import Any, Optional
 
 from six import PY2
 from six.moves import builtins
@@ -26,7 +27,7 @@
 from synapse.storage.database import LoggingTransaction  # noqa: F401
 from synapse.storage.database import make_in_list_sql_clause  # noqa: F401
 from synapse.storage.database import Database
-from synapse.types import get_domain_from_id
+from synapse.types import Collection, get_domain_from_id
 
 logger = logging.getLogger(__name__)
 
@@ -63,17 +64,24 @@ def _invalidate_state_caches(self, room_id, members_changed):
         self._attempt_to_invalidate_cache("get_room_summary", (room_id,))
         self._attempt_to_invalidate_cache("get_current_state_ids", (room_id,))
 
-    def _attempt_to_invalidate_cache(self, cache_name, key):
+    def _attempt_to_invalidate_cache(
+        self, cache_name: str, key: Optional[Collection[Any]]
+    ):
         """Attempts to invalidate the cache of the given name, ignoring if the
         cache doesn't exist. Mainly used for invalidating caches on workers,
         where they may not have the cache.
 
         Args:
-            cache_name (str)
-            key (tuple)
+            cache_name
+            key: Entry to invalidate. If None then invalidates the entire
+                cache.
         """
+
         try:
-            getattr(self, cache_name).invalidate(key)
+            if key is None:
+                getattr(self, cache_name).invalidate_all()
+            else:
+                getattr(self, cache_name).invalidate(tuple(key))
         except AttributeError:
             # We probably haven't pulled in the cache in this worker,
             # which is fine.

synapse/storage/data_stores/main/cache.py

@@ -16,6 +16,7 @@
 
 import itertools
 import logging
+from typing import Any, Iterable, Optional
 
 from twisted.internet import defer
 
@@ -43,6 +44,14 @@ def _invalidate_cache_and_stream(self, txn, cache_func, keys):
         txn.call_after(cache_func.invalidate, keys)
         self._send_invalidation_to_replication(txn, cache_func.__name__, keys)
 
+    def _invalidate_all_cache_and_stream(self, txn, cache_func):
+        """Invalidates the entire cache and adds it to the cache stream so slaves
+        will know to invalidate their caches.
+        """
+
+        txn.call_after(cache_func.invalidate_all)
+        self._send_invalidation_to_replication(txn, cache_func.__name__, None)
+
     def _invalidate_state_caches_and_stream(self, txn, room_id, members_changed):
         """Special case invalidation of caches based on current state.
 
@@ -73,17 +82,24 @@ def _invalidate_state_caches_and_stream(self, txn, room_id, members_changed):
                 txn, CURRENT_STATE_CACHE_NAME, [room_id]
             )
 
-    def _send_invalidation_to_replication(self, txn, cache_name, keys):
+    def _send_invalidation_to_replication(
+        self, txn, cache_name: str, keys: Optional[Iterable[Any]]
+    ):
         """Notifies replication that given cache has been invalidated.
 
         Note that this does *not* invalidate the cache locally.
 
         Args:
             txn
-            cache_name (str)
-            keys (iterable[str])
+            cache_name
+            keys: Entry to invalidate. If None will invalidate all.
         """
 
+        if cache_name == CURRENT_STATE_CACHE_NAME and keys is None:
+            raise Exception(
+                "Can't stream invalidate all with magic current state cache"
+            )
+
         if isinstance(self.database_engine, PostgresEngine):
             # get_next() returns a context manager which is designed to wrap
             # the transaction. However, we want to only get an ID when we want
@@ -95,13 +111,16 @@ def _send_invalidation_to_replication(self, txn, cache_name, keys):
             txn.call_after(ctx.__exit__, None, None, None)
             txn.call_after(self.hs.get_notifier().on_new_replication_data)
 
+            if keys is not None:
+                keys = list(keys)
+
             self.db.simple_insert_txn(
                 txn,
                 table="cache_invalidation_stream",
                 values={
                     "stream_id": stream_id,
                     "cache_func": cache_name,
-                    "keys": list(keys),
+                    "keys": keys,
                     "invalidation_ts": self.clock.time_msec(),
                 },
             )