Fix the openai benchmarking requests to work with latest OpenAI apis (#2992)

Co-authored-by: Roger Wang <136131678+ywang96@users.noreply.github.com>

benchmarks/backend_request_func.py

@@ -275,10 +275,80 @@ async def async_request_openai_completions(
     return output
 
 
+async def async_request_openai_chat_completions(
+    request_func_input: RequestFuncInput,
+    pbar: Optional[tqdm] = None,
+) -> RequestFuncOutput:
+    api_url = request_func_input.api_url
+    assert api_url.endswith(
+        "v1/chat/completions"
+    ), "OpenAI Chat API URL must end with 'v1/chat/completions'."
+
+    async with aiohttp.ClientSession(timeout=AIOHTTP_TIMEOUT) as session:
+        assert not request_func_input.use_beam_search
+        payload = {
+            "model": request_func_input.model,
+            "messages": [
+                {
+                    "role": "user",
+                    "content": request_func_input.prompt,
+                },
+            ],
+            "temperature": 0.0,
+            "max_tokens": request_func_input.output_len,
+            "stream": True,
+        }
+        headers = {
+            "Content-Type": "application/json",
+            "Authorization": f"Bearer {os.environ.get('OPENAI_API_KEY')}"
+        }
+
+        output = RequestFuncOutput()
+        output.prompt_len = request_func_input.prompt_len
+
+        generated_text = ""
+        ttft = 0
+        st = time.perf_counter()
+        try:
+            async with session.post(url=api_url, json=payload,
+                                    headers=headers) as response:
+                if response.status == 200:
+                    async for chunk in response.content:
+                        if ttft == 0:
+                            ttft = time.perf_counter() - st
+                            output.ttft = ttft
+
+                        chunk = chunk.strip()
+                        if not chunk:
+                            continue
+
+                        chunk = chunk.decode("utf-8").lstrip("data: ")
+                        if chunk == "[DONE]":
+                            latency = time.perf_counter() - st
+                        else:
+                            body = json.loads(chunk)
+                            if "content" in body["choices"][0]["delta"]:
+                                generated_text += body["choices"][0]["delta"][
+                                    "content"]
+
+                    output.generated_text = generated_text
+                    output.success = True
+                    output.latency = latency
+                else:
+                    output.success = False
+        except (aiohttp.ClientOSError, aiohttp.ServerDisconnectedError):
+            output.success = False
+
+    if pbar:
+        pbar.update(1)
+    return output
+
+
 ASYNC_REQUEST_FUNCS = {
     "tgi": async_request_tgi,
     "vllm": async_request_vllm,
     "deepspeed-mii": async_request_deepspeed_mii,
     "openai": async_request_openai_completions,
+    "openai-chat": async_request_openai_chat_completions,
     "tensorrt-llm": async_request_trt_llm,
 }