Fix tasks running counter

allianceauth/utils/counters.py

@@ -0,0 +1,65 @@
+"""Counters."""
+
+from typing import Optional
+
+from redis import Redis
+
+from django.core.cache import cache
+
+from .cache import get_redis_client
+
+
+class ItemCounter:
+    """A process safe item counter.
+
+    Args:
+        - name: Unique name for the counter
+        - minimum: Counter can not go below the minimum, when set
+        - redis: A Redis client. Will use AA's cache client by default
+    """
+
+    CACHE_KEY_BASE = "allianceauth-item-counter"
+    DEFAULT_CACHE_TIMEOUT = 24 * 3600
+
+    def __init__(
+        self, name: str, minimum: Optional[int] = None, redis: Optional[Redis] = None
+    ) -> None:
+        if not name:
+            raise ValueError("Must define a name")
+
+        self._name = str(name)
+        self._minimum = minimum
+        self._redis = get_redis_client() if not redis else redis
+
+    @property
+    def _cache_key(self) -> str:
+        return f"{self.CACHE_KEY_BASE}-{self._name}"
+
+    def reset(self, init_value: int = 0):
+        """Reset counter to initial value."""
+        with self._redis.lock(f"{self.CACHE_KEY_BASE}-reset"):
+            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)
+
+    def incr(self, delta: int = 1):
+        """Increment counter by delta."""
+        try:
+            cache.incr(self._cache_key, delta)
+        except ValueError:
+            pass
+
+    def decr(self, delta: int = 1):
+        """Decrement counter by delta."""
+        with self._redis.lock(f"{self.CACHE_KEY_BASE}-decr"):
+            if self._minimum is not None and self.value() == self._minimum:
+                return
+            try:
+                cache.decr(self._cache_key, delta)
+            except ValueError:
+                pass
+
+    def value(self) -> Optional[int]:
+        """Return current value or None if not yet initialized."""
+        return cache.get(self._cache_key)

allianceauth/utils/tests/test_counters.py

@@ -0,0 +1,120 @@
+from unittest import TestCase
+from unittest.mock import patch
+
+from allianceauth.utils.counters import ItemCounter
+
+MODULE_PATH = "allianceauth.utils.counters"
+
+COUNTER_NAME = "test-counter"
+
+
+class TestItemCounter(TestCase):
+    def test_can_create_counter(self):
+        # when
+        counter = ItemCounter(COUNTER_NAME)
+        # then
+        self.assertIsInstance(counter, ItemCounter)
+
+    def test_can_reset_counter_to_default(self):
+        # given
+        counter = ItemCounter(COUNTER_NAME)
+        # when
+        counter.reset()
+        # then
+        self.assertEqual(counter.value(), 0)
+
+    def test_can_reset_counter_to_custom_value(self):
+        # given
+        counter = ItemCounter(COUNTER_NAME)
+        # when
+        counter.reset(42)
+        # then
+        self.assertEqual(counter.value(), 42)
+
+    def test_can_increment_counter_by_default(self):
+        # given
+        counter = ItemCounter(COUNTER_NAME)
+        counter.reset(0)
+        # when
+        counter.incr()
+        # then
+        self.assertEqual(counter.value(), 1)
+
+    def test_can_increment_counter_by_custom_value(self):
+        # given
+        counter = ItemCounter(COUNTER_NAME)
+        counter.reset(0)
+        # when
+        counter.incr(8)
+        # then
+        self.assertEqual(counter.value(), 8)
+
+    def test_can_decrement_counter_by_default(self):
+        # given
+        counter = ItemCounter(COUNTER_NAME)
+        counter.reset(9)
+        # when
+        counter.decr()
+        # then
+        self.assertEqual(counter.value(), 8)
+
+    def test_can_decrement_counter_by_custom_value(self):
+        # given
+        counter = ItemCounter(COUNTER_NAME)
+        counter.reset(9)
+        # when
+        counter.decr(8)
+        # then
+        self.assertEqual(counter.value(), 1)
+
+    def test_can_decrement_counter_below_zero(self):
+        # given
+        counter = ItemCounter(COUNTER_NAME)
+        counter.reset(0)
+        # when
+        counter.decr(1)
+        # then
+        self.assertEqual(counter.value(), -1)
+
+    def test_can_not_decrement_counter_below_minimum(self):
+        # given
+        counter = ItemCounter(COUNTER_NAME, minimum=0)
+        counter.reset(0)
+        # when
+        counter.decr(1)
+        # then
+        self.assertEqual(counter.value(), 0)
+
+    def test_can_not_reset_counter_below_minimum(self):
+        # given
+        counter = ItemCounter(COUNTER_NAME, minimum=0)
+        # when/then
+        with self.assertRaises(ValueError):
+            counter.reset(-1)
+
+    def test_can_not_init_without_name(self):
+        # when/then
+        with self.assertRaises(ValueError):
+            ItemCounter(name="")
+
+    def test_can_ignore_invalid_values_when_incrementing(self):
+        # given
+        counter = ItemCounter(COUNTER_NAME)
+        counter.reset(0)
+        # when
+        with patch(MODULE_PATH + ".cache.incr") as m:
+            m.side_effect = ValueError
+            counter.incr()
+        # then
+        self.assertEqual(counter.value(), 0)
+
+    def test_can_ignore_invalid_values_when_decrementing(self):
+        # given
+        counter = ItemCounter(COUNTER_NAME)
+        counter.reset(1)
+        # when
+        with patch(MODULE_PATH + ".cache.decr") as m:
+            m.side_effect = ValueError
+            counter.decr()
+        # then
+        self.assertEqual(counter.value(), 1)