chore: KV router Pythonic cleanups (#324)

examples/llm/components/kv_router.py

@@ -113,6 +113,23 @@ class Router:
         metrics: AggregatedMetrics | None,
         token_length: int,
     ):
+        """The cost function for deciding the best worker to route a request to.
+        If there are multiple workers sharing the same optimal cost, then
+        one of them is randomly selected.
+
+        Args:
+            scores (OverlapScores | None): The number of matching blocks between
+                the request and the prefix cache of each worker.
+            metrics (AggregatedMetrics | None): Several worker metrics polled
+                by the `KvMetricsAggregator`, currently including the
+                GPU cache usage, number of waiting requests, and the
+                GPU prefix cache hit rate.
+            token_length (int): The number of tokens in the request.
+
+        Returns:
+            (str, float): The best worker id and the corresponding score.
+        """
+
         worker_scores = {}
         if scores:
             for worker_id, score in scores.scores.items():
@@ -129,15 +146,15 @@ class Router:
             for endpoint in metrics.endpoints:
                 worker_id = endpoint.worker_id
                 worker_metrics[worker_id] = {
-                    "gpu_cache_usage_perc": endpoint.gpu_cache_usage_perc
-                    if hasattr(endpoint, "gpu_cache_usage_perc")
-                    else 0.0,
-                    "num_requests_waiting": endpoint.num_requests_waiting
-                    if hasattr(endpoint, "num_requests_waiting")
-                    else 0.0,
-                    "gpu_prefix_cache_hit_rate": endpoint.gpu_prefix_cache_hit_rate
-                    if hasattr(endpoint, "gpu_prefix_cache_hit_rate")
-                    else 0.0,
+                    "gpu_cache_usage_perc": getattr(
+                        endpoint, "gpu_cache_usage_perc", 0.0
+                    ),
+                    "num_requests_waiting": getattr(
+                        endpoint, "num_requests_waiting", 0.0
+                    ),
+                    "gpu_prefix_cache_hit_rate": getattr(
+                        endpoint, "gpu_prefix_cache_hit_rate", 0.0
+                    ),
                 }
                 max_waiting = max(
                     max_waiting, worker_metrics[worker_id]["num_requests_waiting"]
@@ -179,14 +196,11 @@ class Router:
             return ""
 
         # Select the worker with the highest logit
-        if worker_logits:
         max_logit = max(worker_logits.values())
         best_workers = [
             wid for wid, logit in worker_logits.items() if logit == max_logit
         ]
         best_worker_id = random.choice(best_workers)
-        else:
-            best_worker_id = ""
 
         # Log the metrics for the selected worker
         if best_worker_id: