reader: don't use Decimal class to calculate backoff

nsq/backoff_timer.py

@@ -3,44 +3,37 @@
 from decimal import Decimal
 
 
-def _Decimal(v):
-    if not isinstance(v, Decimal):
-        return Decimal(str(v))
-    return v
-
-
 class BackoffTimer(object):
     """
     This is a timer that is smart about backing off exponentially when there are problems
+
+    Internally, the intervals are tracked as integers so that calculation
+    is less expensive.
     """
     def __init__(self, min_interval, max_interval, ratio=.25, short_length=10, long_length=250):
         assert isinstance(min_interval, (int, float, Decimal))
         assert isinstance(max_interval, (int, float, Decimal))
 
-        self.min_interval = _Decimal(min_interval)
-        self.max_interval = _Decimal(max_interval)
+        self.min_interval = int(float(min_interval) * 1000000)
+        self.max_interval = int(float(max_interval) * 1000000)
 
-        self.max_short_timer = (self.max_interval - self.min_interval) * _Decimal(ratio)
-        self.max_long_timer = (self.max_interval - self.min_interval) * (1 - _Decimal(ratio))
-        self.short_unit = self.max_short_timer / _Decimal(short_length)
-        self.long_unit = self.max_long_timer / _Decimal(long_length)
+        self.max_short_timer = int((self.max_interval - self.min_interval) * float(ratio))
+        self.max_long_timer = int((self.max_interval - self.min_interval) * (1 - float(ratio)))
+        self.short_unit = int(self.max_short_timer / float(short_length))
+        self.long_unit = int(self.max_long_timer / float(long_length))
 
-        self.short_interval = Decimal(0)
-        self.long_interval = Decimal(0)
+        self.short_interval = 0
+        self.long_interval = 0
 
     def success(self):
         """Update the timer to reflect a successfull call"""
-        self.short_interval -= self.short_unit
-        self.long_interval -= self.long_unit
-        self.short_interval = max(self.short_interval, Decimal(0))
-        self.long_interval = max(self.long_interval, Decimal(0))
+        self.short_interval = max(self.short_interval - self.short_unit, 0)
+        self.long_interval = max(self.long_interval - self.long_unit, 0)
 
     def failure(self):
         """Update the timer to reflect a failed call"""
-        self.short_interval += self.short_unit
-        self.long_interval += self.long_unit
-        self.short_interval = min(self.short_interval, self.max_short_timer)
-        self.long_interval = min(self.long_interval, self.max_long_timer)
+        self.short_interval = min(self.short_interval + self.short_unit, self.max_short_timer)
+        self.long_interval = min(self.long_interval + self.long_unit, self.max_long_timer)
 
     def get_interval(self):
-        return float(self.min_interval + self.short_interval + self.long_interval)
+        return (self.min_interval + self.short_interval + self.long_interval) / 1000000.0

tests/test_basic.py

@@ -51,9 +51,9 @@ def test_backoff_timer():
     timer.failure()
     interval = '%0.2f' % timer.get_interval()
     assert interval == '3.19'
-    assert timer.min_interval == Decimal('.1')
-    assert timer.short_interval == Decimal('2.9975')
-    assert timer.long_interval == Decimal('0.089925')
+    assert timer.min_interval == 100000 #Decimal('.1')
+    assert timer.short_interval == 2997500 # Decimal('2.9975')
+    assert timer.long_interval == 89925 #Decimal('0.089925')
 
     timer.failure()
     interval = '%0.2f' % timer.get_interval()