[Fix] Skip `record_sleep_state` logic in `PrometheusStatsLogger` if not in dev mode (#27789)

Signed-off-by: SumanthRH <sumanthrh99@gmail.com>

tests/basic_correctness/test_cumem.py

 # SPDX-License-Identifier: Apache-2.0
 # SPDX-FileCopyrightText: Copyright contributors to the vLLM project
 
+import asyncio
+
 import pytest
 import torch
 
-from vllm import LLM, SamplingParams
+from vllm import LLM, AsyncEngineArgs, AsyncLLMEngine, SamplingParams
 from vllm.device_allocator.cumem import CuMemAllocator
 from vllm.utils.mem_constants import GiB_bytes
 
@@ -201,3 +203,42 @@ def test_deep_sleep():
 
     # cmp output
     assert output[0].outputs[0].text == output2[0].outputs[0].text
+
+
+@create_new_process_for_each_test()
+def test_deep_sleep_async():
+    async def test():
+        model = "hmellor/tiny-random-LlamaForCausalLM"
+        free, total = torch.cuda.mem_get_info()
+        used_bytes_baseline = total - free  # in case other process is running
+        engine_args = AsyncEngineArgs(
+            model=model,
+            enable_sleep_mode=True,
+        )
+
+        llm = AsyncLLMEngine.from_engine_args(engine_args)
+        prompt = "How are you?"
+        sampling_params = SamplingParams(temperature=0, max_tokens=10)
+        outputs = llm.generate(prompt, sampling_params, request_id="test_request_id1")
+        async for output in outputs:
+            pass
+
+        # Put the engine to deep sleep
+        await llm.sleep(level=2)
+
+        await llm.wake_up(tags=["weights"])
+        await llm.collective_rpc("reload_weights")
+        free_gpu_bytes_wake_up_w, total = torch.cuda.mem_get_info()
+        used_bytes = total - free_gpu_bytes_wake_up_w - used_bytes_baseline
+        assert used_bytes < 4 * GiB_bytes
+
+        # now allocate kv cache and cuda graph memory
+        await llm.wake_up(tags=["kv_cache"])
+        outputs2 = llm.generate(prompt, sampling_params, request_id="test_request_id2")
+        async for output2 in outputs2:
+            pass
+
+        # cmp output
+        assert output.outputs[0].text == output2.outputs[0].text
+
+    asyncio.run(test())

vllm/v1/metrics/loggers.py

@@ -1052,6 +1052,9 @@ class PrometheusStatLogger(AggregateStatLoggerBase):
             self.gauge_lora_info.labels(**lora_info_labels).set_to_current_time()
 
     def record_sleep_state(self, sleep: int = 0, level: int = 0):
+        if not envs.VLLM_SERVER_DEV_MODE:
+            return
+
         awake = 1
         discard_all = 0
         weights_offloaded = 0