Fix ValueError: Missing value for tag key(s): model_name,engine. (#19113)

Signed-off-by: Seiji Eicher <seiji@anyscale.com>

tests/v1/metrics/test_ray_metrics.py

@@ -47,12 +47,15 @@ def test_engine_log_metrics_ray(
                 engine_args, stat_loggers=[RayPrometheusStatLogger])
 
             for i, prompt in enumerate(example_prompts):
-                engine.generate(
+                results = engine.generate(
                     request_id=f"request-id-{i}",
                     prompt=prompt,
                     sampling_params=SamplingParams(max_tokens=max_tokens),
                 )
 
+                async for _ in results:
+                    pass
+
     # Create the actor and call the async method
     actor = EngineTestActor.remote()  # type: ignore[attr-defined]
     ray.get(actor.run.remote())

vllm/v1/metrics/ray_wrappers.py

@@ -31,6 +31,16 @@ class RayPrometheusMetric:
 
             self.metric.set_default_tags(labelskwargs)
 
+        if labels:
+            if len(labels) != len(self.metric._tag_keys):
+                raise ValueError(
+                    "Number of labels must match the number of tag keys. "
+                    f"Expected {len(self.metric._tag_keys)}, got {len(labels)}"
+                )
+
+            self.metric.set_default_tags(
+                dict(zip(self.metric._tag_keys, labels)))
+
         return self