Add type hints to TTL cache.

synapse/http/federation/well_known_resolver.py

@@ -71,8 +71,10 @@
 logger = logging.getLogger(__name__)
 
 
-_well_known_cache = TTLCache("well-known")
-_had_valid_well_known_cache = TTLCache("had-valid-well-known")
+_well_known_cache = TTLCache("well-known")  # type: TTLCache[bytes, Optional[bytes]]
+_had_valid_well_known_cache = TTLCache(
+    "had-valid-well-known"
+)  # type: TTLCache[bytes, bool]
 
 
 @attr.s(slots=True, frozen=True)
@@ -88,8 +90,8 @@ def __init__(
         reactor: IReactorTime,
         agent: IAgent,
         user_agent: bytes,
-        well_known_cache: Optional[TTLCache] = None,
-        had_well_known_cache: Optional[TTLCache] = None,
+        well_known_cache: Optional[TTLCache[bytes, Optional[bytes]]] = None,
+        had_well_known_cache: Optional[TTLCache[bytes, bool]] = None,
     ):
         self._reactor = reactor
         self._clock = Clock(reactor)

synapse/util/caches/ttlcache.py

@@ -15,6 +15,7 @@
 
 import logging
 import time
+from typing import Callable, Dict, Generic, Tuple, TypeVar, Union
 
 import attr
 from sortedcontainers import SortedList
@@ -25,41 +26,46 @@
 
 SENTINEL = object()
 
+T = TypeVar("T")
+KT = TypeVar("KT")
+VT = TypeVar("VT")
 
-class TTLCache:
+
+class TTLCache(Generic[KT, VT]):
     """A key/value cache implementation where each entry has its own TTL"""
 
-    def __init__(self, cache_name, timer=time.time):
+    def __init__(self, cache_name: str, timer: Callable[[], float] = time.time):
         # map from key to _CacheEntry
-        self._data = {}
+        self._data = {}  # type: Dict[KT, _CacheEntry[KT, VT]]
 
         # the _CacheEntries, sorted by expiry time
-        self._expiry_list = SortedList()  # type: SortedList[_CacheEntry]
+        self._expiry_list = SortedList()  # type: SortedList[_CacheEntry[KT, VT]]
 
         self._timer = timer
 
         self._metrics = register_cache("ttl", cache_name, self, resizable=False)
 
-    def set(self, key, value, ttl):
+    def set(self, key: KT, value: VT, ttl: float) -> None:
         """Add/update an entry in the cache
 
         Args:
             key: key for this entry
             value: value for this entry
-            ttl (float): TTL for this entry, in seconds
+            ttl: TTL for this entry, in seconds
         """
         expiry = self._timer() + ttl
 
         self.expire()
         e = self._data.pop(key, SENTINEL)
-        if e != SENTINEL:
+        if e is not SENTINEL:
+            assert isinstance(e, _CacheEntry)
             self._expiry_list.remove(e)
 
         entry = _CacheEntry(expiry_time=expiry, ttl=ttl, key=key, value=value)
         self._data[key] = entry
         self._expiry_list.add(entry)
 
-    def get(self, key, default=SENTINEL):
+    def get(self, key: KT, default: T = SENTINEL) -> Union[VT, T]:  # type: ignore
         """Get a value from the cache
 
         Args:
@@ -72,23 +78,23 @@ def get(self, key, default=SENTINEL):
         """
         self.expire()
         e = self._data.get(key, SENTINEL)
-        if e == SENTINEL:
+        if e is SENTINEL:
             self._metrics.inc_misses()
-            if default == SENTINEL:
+            if default is SENTINEL:
                 raise KeyError(key)
             return default
+        assert isinstance(e, _CacheEntry)
         self._metrics.inc_hits()
         return e.value
 
-    def get_with_expiry(self, key):
+    def get_with_expiry(self, key: KT) -> Tuple[VT, float, float]:
         """Get a value, and its expiry time, from the cache
 
         Args:
             key: key to look up
 
         Returns:
-            Tuple[Any, float, float]: the value from the cache, the expiry time
-            and the TTL
+            A tuple of  the value from the cache, the expiry time and the TTL
 
         Raises:
             KeyError if the entry is not found
@@ -102,7 +108,7 @@ def get_with_expiry(self, key):
         self._metrics.inc_hits()
         return e.value, e.expiry_time, e.ttl
 
-    def pop(self, key, default=SENTINEL):
+    def pop(self, key: KT, default: T = SENTINEL) -> Union[VT, T]:  # type: ignore
         """Remove a value from the cache
 
         If key is in the cache, remove it and return its value, else return default.
@@ -118,29 +124,30 @@ def pop(self, key, default=SENTINEL):
         """
         self.expire()
         e = self._data.pop(key, SENTINEL)
-        if e == SENTINEL:
+        if e is SENTINEL:
             self._metrics.inc_misses()
-            if default == SENTINEL:
+            if default is SENTINEL:
                 raise KeyError(key)
             return default
+        assert isinstance(e, _CacheEntry)
         self._expiry_list.remove(e)
         self._metrics.inc_hits()
         return e.value
 
-    def __getitem__(self, key):
+    def __getitem__(self, key: KT) -> VT:
         return self.get(key)
 
-    def __delitem__(self, key):
+    def __delitem__(self, key: KT) -> None:
         self.pop(key)
 
-    def __contains__(self, key):
+    def __contains__(self, key: KT) -> bool:
         return key in self._data
 
-    def __len__(self):
+    def __len__(self) -> int:
         self.expire()
         return len(self._data)
 
-    def expire(self):
+    def expire(self) -> None:
         """Run the expiry on the cache. Any entries whose expiry times are due will
         be removed
         """
@@ -154,11 +161,11 @@ def expire(self):
 
 
 @attr.s(frozen=True, slots=True)
-class _CacheEntry:
+class _CacheEntry(Generic[KT, VT]):
     """TTLCache entry"""
 
     # expiry_time is the first attribute, so that entries are sorted by expiry.
-    expiry_time = attr.ib()
-    ttl = attr.ib()
-    key = attr.ib()
-    value = attr.ib()
+    expiry_time = attr.ib(type=float)
+    ttl = attr.ib(type=float)
+    key = attr.ib()  # type: KT
+    value = attr.ib()  # type: VT