fix: simple jitter

Author: exiaohu

volcenginesdkarkruntime/_utils/_model_breaker.py

@@ -1,4 +1,5 @@
 from datetime import datetime, timedelta
+import random
 
 
 class ModelBreaker:
@@ -17,7 +18,12 @@ def reset(self, duration):
     def get_allowed_duration(self):
         # 计算当前时间与 allow_time 之间的持续时间
         allow_duration = self.allow_time - datetime.now()
+
+        # 添加一个随机抖动，该抖动的范围为 0 到 10 秒，概率密度函数为 f(x) = x/50 (0 <= x <= 10)
+        # 约有 1/100 的请求会在结束熔断的第一秒内发起重试
+        jitter = timedelta(seconds=random.triangular(0, 10, 10))
+
         # 如果持续时间为负，则返回一个零时长的 timedelta 对象
         if allow_duration.total_seconds() < 0:
-            return timedelta(0)
-        return allow_duration
+            return timedelta(0) + jitter
+        return allow_duration + jitter