1 files changed, 105 insertions, 0 deletions
diff --git a/redis/backoff.py b/redis/backoff.py
new file mode 100644
index 0000000..9162778
--- /dev/null
+++ b/redis/backoff.py
@@ -0,0 +1,105 @@
+from abc import ABC, abstractmethod
+import random
+
+
+class AbstractBackoff(ABC):
+    """Backoff interface"""
+
+    def reset(self):
+        """
+        Reset internal state before an operation.
+        `reset` is called once at the beginning of
+        every call to `Retry.call_with_retry`
+        """
+        pass
+
+    @abstractmethod
+    def compute(self, failures):
+        """Compute backoff in seconds upon failure"""
+        pass
+
+
+class ConstantBackoff(AbstractBackoff):
+    """Constant backoff upon failure"""
+
+    def __init__(self, backoff):
+        """`backoff`: backoff time in seconds"""
+        self._backoff = backoff
+
+    def compute(self, failures):
+        return self._backoff
+
+
+class NoBackoff(ConstantBackoff):
+    """No backoff upon failure"""
+
+    def __init__(self):
+        super().__init__(0)
+
+
+class ExponentialBackoff(AbstractBackoff):
+    """Exponential backoff upon failure"""
+
+    def __init__(self, cap, base):
+        """
+        `cap`: maximum backoff time in seconds
+        `base`: base backoff time in seconds
+        """
+        self._cap = cap
+        self._base = base
+
+    def compute(self, failures):
+        return min(self._cap, self._base * 2 ** failures)
+
+
+class FullJitterBackoff(AbstractBackoff):
+    """Full jitter backoff upon failure"""
+
+    def __init__(self, cap, base):
+        """
+        `cap`: maximum backoff time in seconds
+        `base`: base backoff time in seconds
+        """
+        self._cap = cap
+        self._base = base
+
+    def compute(self, failures):
+        return random.uniform(0, min(self._cap, self._base * 2 ** failures))
+
+
+class EqualJitterBackoff(AbstractBackoff):
+    """Equal jitter backoff upon failure"""
+
+    def __init__(self, cap, base):
+        """
+        `cap`: maximum backoff time in seconds
+        `base`: base backoff time in seconds
+        """
+        self._cap = cap
+        self._base = base
+
+    def compute(self, failures):
+        temp = min(self._cap, self._base * 2 ** failures) / 2
+        return temp + random.uniform(0, temp)
+
+
+class DecorrelatedJitterBackoff(AbstractBackoff):
+    """Decorrelated jitter backoff upon failure"""
+
+    def __init__(self, cap, base):
+        """
+        `cap`: maximum backoff time in seconds
+        `base`: base backoff time in seconds
+        """
+        self._cap = cap
+        self._base = base
+        self._previous_backoff = 0
+
+    def reset(self):
+        self._previous_backoff = 0
+
+    def compute(self, failures):
+        max_backoff = max(self._base, self._previous_backoff * 3)
+        temp = random.uniform(self._base, max_backoff)
+        self._previous_backoff = min(self._cap, temp)
+        return self._previous_backoff