add configurable thread scaling and queue counter reset

- Add scale_cooldown and scale_threshold config options
- ThreadScaler now reads scaling params from config
- Reset priority queue counter when queue empties to prevent unbounded growth

proxywatchd.py

@@ -963,6 +963,9 @@ class PriorityJobQueue(object):
     def put(self, job, priority=3):
         """Add job with priority (lower = higher priority)."""
         with self.lock:
+            # Reset counter when queue was empty to prevent unbounded growth
+            if not self.heap:
+                self.counter = 0
             heapq.heappush(self.heap, (priority, self.counter, job))
             self.counter += 1
             self.not_empty.notify()
@@ -1042,13 +1045,14 @@ class ThreadScaler(object):
         - Success rate drops below threshold
     """
 
-    def __init__(self, min_threads=5, max_threads=100, target_queue_per_thread=5):
+    def __init__(self, min_threads=5, max_threads=100, target_queue_per_thread=5,
+                 scale_cooldown=10, scale_threshold=10.0):
         self.min_threads = min_threads
         self.max_threads = max_threads
         self.target_queue_per_thread = target_queue_per_thread
         self.last_scale_time = 0
-        self.scale_cooldown = 10  # seconds between scaling (faster with greenlets)
-        self.success_threshold = 10.0  # minimum success rate % to scale up
+        self.scale_cooldown = scale_cooldown
+        self.success_threshold = scale_threshold
 
     def should_scale(self, current_threads, queue_size, stats):
         """Determine if scaling is needed.
@@ -1771,8 +1775,10 @@ class Proxywatchd():
         min_t = config.watchd.min_threads if config.watchd.min_threads > 0 else max(5, config.watchd.threads // 4)
         self.scaler = ThreadScaler(
             min_threads=min_t,
-            max_threads=config.watchd.threads,  # respect configured thread limit
-            target_queue_per_thread=5
+            max_threads=config.watchd.threads,
+            target_queue_per_thread=5,
+            scale_cooldown=config.watchd.scale_cooldown,
+            scale_threshold=config.watchd.scale_threshold
         )
         self.thread_id_counter = 0
         self.last_jobs_log = 0