Add type hints to response cache. (#8507)

changelog.d/8507.misc

@@ -0,0 +1 @@
+ Add type hints to various parts of the code base.

mypy.ini

@@ -65,6 +65,7 @@ files =
   synapse/types.py,
   synapse/util/async_helpers.py,
   synapse/util/caches/descriptors.py,
+  synapse/util/caches/response_cache.py,
   synapse/util/caches/stream_change_cache.py,
   synapse/util/metrics.py,
   tests/replication,

synapse/appservice/api.py

@@ -14,7 +14,7 @@
 # limitations under the License.
 import logging
 import urllib
-from typing import TYPE_CHECKING, Optional
+from typing import TYPE_CHECKING, Optional, Tuple
 
 from prometheus_client import Counter
 
@@ -93,7 +93,7 @@ def __init__(self, hs):
 
         self.protocol_meta_cache = ResponseCache(
             hs, "as_protocol_meta", timeout_ms=HOUR_IN_MS
-        )
+        )  # type: ResponseCache[Tuple[str, str]]
 
     async def query_user(self, service, user_id):
         if service.url is None:

synapse/federation/federation_server.py

@@ -116,18 +116,20 @@ def __init__(self, hs):
         # We cache results for transaction with the same ID
         self._transaction_resp_cache = ResponseCache(
             hs, "fed_txn_handler", timeout_ms=30000
-        )
+        )  # type: ResponseCache[Tuple[str, str]]
 
         self.transaction_actions = TransactionActions(self.store)
 
         self.registry = hs.get_federation_registry()
 
         # We cache responses to state queries, as they take a while and often
         # come in waves.
-        self._state_resp_cache = ResponseCache(hs, "state_resp", timeout_ms=30000)
+        self._state_resp_cache = ResponseCache(
+            hs, "state_resp", timeout_ms=30000
+        )  # type: ResponseCache[Tuple[str, str]]
         self._state_ids_resp_cache = ResponseCache(
             hs, "state_ids_resp", timeout_ms=30000
-        )
+        )  # type: ResponseCache[Tuple[str, str]]
 
         self._federation_metrics_domains = (
             hs.get_config().federation.federation_metrics_domains

synapse/handlers/initial_sync.py

@@ -14,7 +14,7 @@
 # limitations under the License.
 
 import logging
-from typing import TYPE_CHECKING
+from typing import TYPE_CHECKING, Optional, Tuple
 
 from twisted.internet import defer
 
@@ -47,12 +47,14 @@ def __init__(self, hs: "HomeServer"):
         self.state = hs.get_state_handler()
         self.clock = hs.get_clock()
         self.validator = EventValidator()
-        self.snapshot_cache = ResponseCache(hs, "initial_sync_cache")
+        self.snapshot_cache = ResponseCache(
+            hs, "initial_sync_cache"
+        )  # type: ResponseCache[Tuple[str, Optional[StreamToken], Optional[StreamToken], str, Optional[int], bool, bool]]
         self._event_serializer = hs.get_event_client_serializer()
         self.storage = hs.get_storage()
         self.state_store = self.storage.state
 
-    def snapshot_all_rooms(
+    async def snapshot_all_rooms(
         self,
         user_id: str,
         pagin_config: PaginationConfig,
@@ -84,7 +86,7 @@ def snapshot_all_rooms(
             include_archived,
         )
 
-        return self.snapshot_cache.wrap(
+        return await self.snapshot_cache.wrap(
             key,
             self._snapshot_all_rooms,
             user_id,

synapse/handlers/room.py

@@ -120,7 +120,7 @@ def __init__(self, hs: "HomeServer"):
         # subsequent requests
         self._upgrade_response_cache = ResponseCache(
             hs, "room_upgrade", timeout_ms=FIVE_MINUTES_IN_MS
-        )
+        )  # type: ResponseCache[Tuple[str, str]]
         self._server_notices_mxid = hs.config.server_notices_mxid
 
         self.third_party_event_rules = hs.get_third_party_event_rules()

synapse/handlers/sync.py

@@ -243,7 +243,9 @@ def __init__(self, hs: "HomeServer"):
         self.presence_handler = hs.get_presence_handler()
         self.event_sources = hs.get_event_sources()
         self.clock = hs.get_clock()
-        self.response_cache = ResponseCache(hs, "sync")
+        self.response_cache = ResponseCache(
+            hs, "sync"
+        )  # type: ResponseCache[Tuple[Any, ...]]
         self.state = hs.get_state_handler()
         self.auth = hs.get_auth()
         self.storage = hs.get_storage()

synapse/replication/http/_base.py

@@ -92,7 +92,7 @@ def __init__(self, hs):
         if self.CACHE:
             self.response_cache = ResponseCache(
                 hs, "repl." + self.NAME, timeout_ms=30 * 60 * 1000
-            )
+            )  # type: ResponseCache[str]
 
         # We reserve `instance_name` as a parameter to sending requests, so we
         # assert here that sub classes don't try and use the name.

synapse/util/caches/response_cache.py

@@ -13,40 +13,47 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 import logging
+from typing import TYPE_CHECKING, Any, Callable, Dict, Generic, Optional, TypeVar
 
 from twisted.internet import defer
 
 from synapse.logging.context import make_deferred_yieldable, run_in_background
 from synapse.util.async_helpers import ObservableDeferred
 from synapse.util.caches import register_cache
 
+if TYPE_CHECKING:
+    from synapse.app.homeserver import HomeServer
+
 logger = logging.getLogger(__name__)
 
+T = TypeVar("T")
+
 
-class ResponseCache:
+class ResponseCache(Generic[T]):
     """
     This caches a deferred response. Until the deferred completes it will be
     returned from the cache. This means that if the client retries the request
     while the response is still being computed, that original response will be
     used rather than trying to compute a new response.
     """
 
-    def __init__(self, hs, name, timeout_ms=0):
-        self.pending_result_cache = {}  # Requests that haven't finished yet.
+    def __init__(self, hs: "HomeServer", name: str, timeout_ms: float = 0):
+        # Requests that haven't finished yet.
+        self.pending_result_cache = {}  # type: Dict[T, ObservableDeferred]
 
         self.clock = hs.get_clock()
         self.timeout_sec = timeout_ms / 1000.0
 
         self._name = name
         self._metrics = register_cache("response_cache", name, self, resizable=False)
 
-    def size(self):
+    def size(self) -> int:
         return len(self.pending_result_cache)
 
-    def __len__(self):
+    def __len__(self) -> int:
         return self.size()
 
-    def get(self, key):
+    def get(self, key: T) -> Optional[defer.Deferred]:
         """Look up the given key.
 
         Can return either a new Deferred (which also doesn't follow the synapse
@@ -58,12 +65,11 @@ def get(self, key):
         from an absent cache entry.
 
         Args:
-            key (hashable):
+            key: key to get/set in the cache
 
         Returns:
-            twisted.internet.defer.Deferred|None|E: None if there is no entry
-            for this key; otherwise either a deferred result or the result
-            itself.
+            None if there is no entry for this key; otherwise a deferred which
+            resolves to the result.
         """
         result = self.pending_result_cache.get(key)
         if result is not None:
@@ -73,7 +79,7 @@ def get(self, key):
             self._metrics.inc_misses()
             return None
 
-    def set(self, key, deferred):
+    def set(self, key: T, deferred: defer.Deferred) -> defer.Deferred:
         """Set the entry for the given key to the given deferred.
 
         *deferred* should run its callbacks in the sentinel logcontext (ie,
@@ -85,12 +91,11 @@ def set(self, key, deferred):
         result. You will probably want to make_deferred_yieldable the result.
 
         Args:
-            key (hashable):
-            deferred (twisted.internet.defer.Deferred[T):
+            key: key to get/set in the cache
+            deferred: The deferred which resolves to the result.
 
         Returns:
-            twisted.internet.defer.Deferred[T]|T: a new deferred, or the actual
-                result.
+            A new deferred which resolves to the actual result.
         """
         result = ObservableDeferred(deferred, consumeErrors=True)
         self.pending_result_cache[key] = result
@@ -107,7 +112,9 @@ def remove(r):
         result.addBoth(remove)
         return result.observe()
 
-    def wrap(self, key, callback, *args, **kwargs):
+    def wrap(
+        self, key: T, callback: "Callable[..., Any]", *args: Any, **kwargs: Any
+    ) -> defer.Deferred:
         """Wrap together a *get* and *set* call, taking care of logcontexts
 
         First looks up the key in the cache, and if it is present makes it
@@ -118,29 +125,28 @@ def wrap(self, key, callback, *args, **kwargs):
 
         Example usage:
 
-            @defer.inlineCallbacks
-            def handle_request(request):
+            async def handle_request(request):
                 # etc
                 return result
 
-            result = yield response_cache.wrap(
+            result = await response_cache.wrap(
                 key,
                 handle_request,
                 request,
             )
 
         Args:
-            key (hashable): key to get/set in the cache
+            key: key to get/set in the cache
 
-            callback (callable): function to call if the key is not found in
+            callback: function to call if the key is not found in
                 the cache
 
             *args: positional parameters to pass to the callback, if it is used
 
             **kwargs: named parameters to pass to the callback, if it is used
 
         Returns:
-            twisted.internet.defer.Deferred: yieldable result
+            Deferred which resolves to the result
         """
         result = self.get(key)
         if not result: