Add locks to ensure process safety

allianceauth/authentication/task_statistics/helpers.py

@@ -3,11 +3,12 @@
 import logging
 from typing import Optional
 
-from app_utils.allianceauth import get_redis_client
 from redis import Redis, RedisError
 
 from django.core.cache import cache
 
+from allianceauth.utils.cache import get_redis_client
+
 logger = logging.getLogger(__name__)
 
 
@@ -56,7 +57,7 @@ class ItemCounter:
 
         self._name = str(name)
         self._minimum = minimum
-        self._redis = redis if redis else get_redis_client()
+        self._redis = get_redis_client_or_stub() if not redis else redis
 
     @property
     def _cache_key(self) -> str:
@@ -64,10 +65,11 @@ class ItemCounter:
 
     def reset(self, init_value: int = 0):
         """Reset counter to initial value."""
-        if self._minimum is not None and init_value < self._minimum:
+        with self._redis.lock(f"{self.CACHE_KEY_BASE}-reset"):
-            raise ValueError("Can not reset below minimum")
+            if self._minimum is not None and init_value < self._minimum:
+                raise ValueError("Can not reset below minimum")
 
-        cache.set(self._cache_key, init_value, self.DEFAULT_CACHE_TIMEOUT)
+            cache.set(self._cache_key, init_value, self.DEFAULT_CACHE_TIMEOUT)
 
     def incr(self, delta: int = 1):
         """Increment counter by delta."""
@@ -78,19 +80,20 @@ class ItemCounter:
 
     def decr(self, delta: int = 1):
         """Decrement counter by delta."""
-        if self._minimum is not None and self.value() == self._minimum:
+        with self._redis.lock(f"{self.CACHE_KEY_BASE}-decr"):
-            return
+            if self._minimum is not None and self.value() == self._minimum:
-        try:
+                return
-            cache.decr(self._cache_key, delta)
+            try:
-        except ValueError:
+                cache.decr(self._cache_key, delta)
-            pass
+            except ValueError:
+                pass
 
     def value(self) -> Optional[int]:
         """Return current value or None if not yet initialized."""
         return cache.get(self._cache_key)
 
 
-def get_redis_client_or_stub():
+def get_redis_client_or_stub() -> Redis:
     """Return AA's default cache client or a stub if Redis is not available."""
     redis = get_redis_client()
     try: