Add cache invalidation across workers to module API

Signed-off-by: Mathieu Velten <mathieuv@matrix.org>

changelog.d/13667.feature

@@ -0,0 +1 @@
+Add cache invalidation across workers to module API.

scripts-dev/mypy_synapse_plugin.py

@@ -29,7 +29,7 @@ def get_method_signature_hook(
         self, fullname: str
     ) -> Optional[Callable[[MethodSigContext], CallableType]]:
         if fullname.startswith(
-            "synapse.util.caches.descriptors._CachedFunction.__call__"
+            "synapse.util.caches.descriptors.CachedFunction.__call__"
         ) or fullname.startswith(
             "synapse.util.caches.descriptors._LruCachedFunction.__call__"
         ):
@@ -38,7 +38,7 @@ def get_method_signature_hook(
 
 
 def cached_function_method_signature(ctx: MethodSigContext) -> CallableType:
-    """Fixes the `_CachedFunction.__call__` signature to be correct.
+    """Fixes the `CachedFunction.__call__` signature to be correct.
 
     It already has *almost* the correct signature, except:
 

synapse/module_api/__init__.py

@@ -122,7 +122,7 @@
 )
 from synapse.util import Clock
 from synapse.util.async_helpers import maybe_awaitable
-from synapse.util.caches.descriptors import cached
+from synapse.util.caches.descriptors import CachedFunction, cached
 from synapse.util.frozenutils import freeze
 
 if TYPE_CHECKING:
@@ -827,6 +827,20 @@ def run_db_interaction(
             self._store.db_pool.runInteraction(desc, func, *args, **kwargs)  # type: ignore[arg-type]
         )
 
+    async def invalidate_cache(
+        self, cached_func: CachedFunction, keys: Tuple[Any, ...]
+    ) -> None:
+        cached_func.invalidate(keys)
+        await self._store.send_invalidation_to_replication(
+            cached_func.__qualname__,
+            keys,
+        )
+
+    def register_cached_function(self, cached_func: CachedFunction) -> None:
+        self._store.register_external_cached_function(
+            cached_func.__qualname__, cached_func
+        )
+
     def complete_sso_login(
         self, registered_user_id: str, request: SynapseRequest, client_redirect_url: str
     ) -> None:

synapse/storage/_base.py

@@ -81,7 +81,7 @@ def _invalidate_state_caches(
 
     def _attempt_to_invalidate_cache(
         self, cache_name: str, key: Optional[Collection[Any]]
-    ) -> None:
+    ) -> bool:
         """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.
@@ -97,13 +97,15 @@ def _attempt_to_invalidate_cache(
         except AttributeError:
             # We probably haven't pulled in the cache in this worker,
             # which is fine.
-            return
+            return False
 
         if key is None:
             cache.invalidate_all()
         else:
             cache.invalidate(tuple(key))
 
+        return True
+
 
 def db_to_json(db_content: Union[memoryview, bytes, bytearray, str]) -> Any:
     """

synapse/storage/databases/main/cache.py

@@ -32,7 +32,7 @@
     LoggingTransaction,
 )
 from synapse.storage.engines import PostgresEngine
-from synapse.util.caches.descriptors import _CachedFunction
+from synapse.util.caches.descriptors import CachedFunction
 from synapse.util.iterutils import batch_iter
 
 if TYPE_CHECKING:
@@ -57,6 +57,11 @@ def __init__(
 
         self._instance_name = hs.get_instance_name()
 
+        self.external_cached_functions = {}
+
+    def register_external_cached_function(self, cache_name, func):
+        self.external_cached_functions[cache_name] = func
+
     async def get_all_updated_caches(
         self, instance_name: str, last_id: int, current_id: int, limit: int
     ) -> Tuple[List[Tuple[int, tuple]], int, bool]:
@@ -144,7 +149,11 @@ def process_replication_rows(
                     members_changed = set(row.keys[1:])
                     self._invalidate_state_caches(room_id, members_changed)
                 else:
-                    self._attempt_to_invalidate_cache(row.cache_func, row.keys)
+                    res = self._attempt_to_invalidate_cache(row.cache_func, row.keys)
+                    if not res:
+                        external_func = self.external_cached_functions[row.cache_func]
+                        if external_func:
+                            external_func.invalidate(row.keys)
 
         super().process_replication_rows(stream_name, instance_name, token, rows)
 
@@ -237,17 +246,15 @@ async def invalidate_cache_and_stream(
             return
 
         cache_func.invalidate(keys)
-        await self.db_pool.runInteraction(
-            "invalidate_cache_and_stream",
-            self._send_invalidation_to_replication,
+        await self.send_invalidation_to_replication(
             cache_func.__name__,
             keys,
         )
 
     def _invalidate_cache_and_stream(
         self,
         txn: LoggingTransaction,
-        cache_func: _CachedFunction,
+        cache_func: CachedFunction,
         keys: Tuple[Any, ...],
     ) -> None:
         """Invalidates the cache and adds it to the cache stream so slaves
@@ -261,7 +268,7 @@ def _invalidate_cache_and_stream(
         self._send_invalidation_to_replication(txn, cache_func.__name__, keys)
 
     def _invalidate_all_cache_and_stream(
-        self, txn: LoggingTransaction, cache_func: _CachedFunction
+        self, txn: LoggingTransaction, cache_func: CachedFunction
     ) -> None:
         """Invalidates the entire cache and adds it to the cache stream so slaves
         will know to invalidate their caches.
@@ -302,6 +309,14 @@ def _invalidate_state_caches_and_stream(
                 txn, CURRENT_STATE_CACHE_NAME, [room_id]
             )
 
+    async def send_invalidation_to_replication(self, cache_name, keys):
+        await self.db_pool.runInteraction(
+            "send_invalidation_to_replication",
+            self._send_invalidation_to_replication,
+            cache_name,
+            keys,
+        )
+
     def _send_invalidation_to_replication(
         self, txn: LoggingTransaction, cache_name: str, keys: Optional[Iterable[Any]]
     ) -> None:

synapse/util/caches/descriptors.py

@@ -52,7 +52,7 @@
 F = TypeVar("F", bound=Callable[..., Any])
 
 
-class _CachedFunction(Generic[F]):
+class CachedFunction(Generic[F]):
     invalidate: Any = None
     invalidate_all: Any = None
     prefill: Any = None
@@ -239,7 +239,7 @@ def _wrapped(*args: Any, **kwargs: Any) -> Any:
 
             return ret2
 
-        wrapped = cast(_CachedFunction, _wrapped)
+        wrapped = cast(CachedFunction, _wrapped)
         wrapped.cache = cache
         obj.__dict__[self.orig.__name__] = wrapped
 
@@ -358,7 +358,7 @@ def _wrapped(*args: Any, **kwargs: Any) -> Any:
 
             return make_deferred_yieldable(ret)
 
-        wrapped = cast(_CachedFunction, _wrapped)
+        wrapped = cast(CachedFunction, _wrapped)
 
         if self.num_args == 1:
             assert not self.tree
@@ -577,7 +577,7 @@ def cached(
     cache_context: bool = False,
     iterable: bool = False,
     prune_unread_entries: bool = True,
-) -> Callable[[F], _CachedFunction[F]]:
+) -> Callable[[F], CachedFunction[F]]:
     func = lambda orig: DeferredCacheDescriptor(
         orig,
         max_entries=max_entries,
@@ -589,12 +589,12 @@ def cached(
         prune_unread_entries=prune_unread_entries,
     )
 
-    return cast(Callable[[F], _CachedFunction[F]], func)
+    return cast(Callable[[F], CachedFunction[F]], func)
 
 
 def cachedList(
     *, cached_method_name: str, list_name: str, num_args: Optional[int] = None
-) -> Callable[[F], _CachedFunction[F]]:
+) -> Callable[[F], CachedFunction[F]]:
     """Creates a descriptor that wraps a function in a `CacheListDescriptor`.
 
     Used to do batch lookups for an already created cache. A single argument
@@ -629,7 +629,7 @@ def batch_do_something(self, first_arg, second_args):
         num_args=num_args,
     )
 
-    return cast(Callable[[F], _CachedFunction[F]], func)
+    return cast(Callable[[F], CachedFunction[F]], func)
 
 
 def _get_cache_key_builder(

tests/replication/test_module_cache_invalidation.py

@@ -0,0 +1,112 @@
+# Copyright 2022 The Matrix.org Foundation C.I.C.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# 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.
+import logging
+
+import synapse
+from synapse.module_api import cached
+
+from tests.replication._base import BaseMultiWorkerStreamTestCase
+
+logger = logging.getLogger(__name__)
+
+FIRST_VALUE = "one"
+SECOND_VALUE = "two"
+
+KEY = "mykey"
+
+
+class TestCache:
+    current_value = FIRST_VALUE
+
+    @cached()
+    async def cached_function(self, user_id: str) -> str:
+        return self.current_value
+
+
+class ModuleCacheInvalidationTestCase(BaseMultiWorkerStreamTestCase):
+    servlets = [
+        synapse.rest.admin.register_servlets,
+    ]
+
+    def test_module_cache_local_invalidation_only(self):
+        main_cache = TestCache()
+
+        self.make_worker_hs("synapse.app.generic_worker")
+
+        worker_cache = TestCache()
+
+        self.assertEqual(FIRST_VALUE, self.get_success(main_cache.cached_function(KEY)))
+        self.assertEqual(
+            FIRST_VALUE, self.get_success(worker_cache.cached_function(KEY))
+        )
+
+        main_cache.current_value = SECOND_VALUE
+        worker_cache.current_value = SECOND_VALUE
+        # No local invalidation yet, should return the cached value on both the main process and the worker
+        self.assertEqual(FIRST_VALUE, self.get_success(main_cache.cached_function(KEY)))
+        self.assertEqual(
+            FIRST_VALUE, self.get_success(worker_cache.cached_function(KEY))
+        )
+
+        # local invalidation on the main process, worker should still return the cached value
+        main_cache.cached_function.invalidate((KEY,))
+        self.assertEqual(
+            SECOND_VALUE, self.get_success(main_cache.cached_function(KEY))
+        )
+        self.assertEqual(
+            FIRST_VALUE, self.get_success(worker_cache.cached_function(KEY))
+        )
+
+    def test_module_cache_full_invalidation(self):
+        # This is supposed to be useless, but something definitively
+        # get initialized regarding replication there since it doesn't work without it
+        self.register_user("user", "pass")
+
+        main_cache = TestCache()
+        self.hs.get_module_api().register_cached_function(main_cache.cached_function)
+
+        worker_hs = self.make_worker_hs("synapse.app.generic_worker")
+
+        worker_cache = TestCache()
+        worker_hs.get_module_api().register_cached_function(
+            worker_cache.cached_function
+        )
+
+        self.assertEqual(FIRST_VALUE, self.get_success(main_cache.cached_function(KEY)))
+        self.assertEqual(
+            FIRST_VALUE, self.get_success(worker_cache.cached_function(KEY))
+        )
+
+        main_cache.current_value = SECOND_VALUE
+        worker_cache.current_value = SECOND_VALUE
+        # No invalidation yet, should return the cached value on both the main process and the worker
+        self.assertEqual(FIRST_VALUE, self.get_success(main_cache.cached_function(KEY)))
+        self.assertEqual(
+            FIRST_VALUE, self.get_success(worker_cache.cached_function(KEY))
+        )
+
+        # Full invalidation on the main process, should be replicated on the worker that
+        # should returned the updated value too
+        self.get_success(
+            self.hs.get_module_api().invalidate_cache(
+                main_cache.cached_function, (KEY,)
+            )
+        )
+
+        self.assertEqual(
+            SECOND_VALUE, self.get_success(main_cache.cached_function(KEY))
+        )
+        self.assertEqual(
+            SECOND_VALUE, self.get_success(worker_cache.cached_function(KEY))
+        )