[Frontend] Add Usage data in each chunk for chat_serving. vllm-project#6540 (vllm-project#6652)

Signed-off-by: LeiWang1999 <leiwang1999@outlook.com>

Author: yecohn

tests/entrypoints/openai/test_chat.py

@@ -295,14 +295,19 @@ async def test_chat_completion_stream_options(client: openai.AsyncOpenAI,
     async for chunk in stream:
         assert chunk.usage is None
 
-    # Test stream=True, stream_options={"include_usage": True}
-    stream = await client.chat.completions.create(
-        model=model_name,
-        messages=messages,
-        max_tokens=10,
-        temperature=0.0,
-        stream=True,
-        stream_options={"include_usage": True})
+    # Test stream=True, stream_options={"include_usage": True,
+    #                                   "continuous_usage_stats": False}}
+    stream = await client.chat.completions.create(model=model_name,
+                                                  messages=messages,
+                                                  max_tokens=10,
+                                                  temperature=0.0,
+                                                  stream=True,
+                                                  stream_options={
+                                                      "include_usage":
+                                                      True,
+                                                      "continuous_usage_stats":
+                                                      False
+                                                  })
 
     async for chunk in stream:
         if chunk.choices[0].finish_reason is None:
@@ -338,6 +343,25 @@ async def test_chat_completion_stream_options(client: openai.AsyncOpenAI,
             stream=False,
             stream_options={"include_usage": True})
 
+    # Test stream=True, stream_options={"include_usage": True,
+    #                           "continuous_usage_stats": True}
+    stream = await client.chat.completions.create(
+        model=model_name,
+        messages=messages,
+        max_tokens=10,
+        temperature=0.0,
+        stream=True,
+        stream_options={
+            "include_usage": True,
+            "continuous_usage_stats": True
+        },
+    )
+    async for chunk in stream:
+        assert chunk.usage.prompt_tokens >= 0
+        assert chunk.usage.completion_tokens >= 0
+        assert chunk.usage.total_tokens == (chunk.usage.prompt_tokens +
+                                            chunk.usage.completion_tokens)
+
 
 # NOTE: Not sure why, but when I place this after `test_guided_regex_chat`
 # (i.e. using the same ordering as in the Completions API tests), the test

vllm/entrypoints/openai/serving_chat.py

@@ -247,7 +247,15 @@ async def chat_completion_stream_generator(
                             model=model_name)
                         if (request.stream_options
                                 and request.stream_options.include_usage):
-                            chunk.usage = None
+                            if (request.stream_options.continuous_usage_stats):
+                                prompt_tokens = len(res.prompt_token_ids)
+                                usage = UsageInfo(prompt_tokens=prompt_tokens,
+                                                  completion_tokens=0,
+                                                  total_tokens=prompt_tokens)
+                                chunk.usage = usage
+                            else:
+                                chunk.usage = None
+
                         data = chunk.model_dump_json(exclude_unset=True)
                         yield f"data: {data}\n\n"
 
@@ -277,7 +285,18 @@ async def chat_completion_stream_generator(
                                     model=model_name)
                                 if (request.stream_options and
                                         request.stream_options.include_usage):
-                                    chunk.usage = None
+                                    if (request.stream_options.
+                                            continuous_usage_stats):
+                                        prompt_tokens = len(
+                                            res.prompt_token_ids)
+                                        usage = UsageInfo(
+                                            prompt_tokens=prompt_tokens,
+                                            completion_tokens=0,
+                                            total_tokens=prompt_tokens)
+                                        chunk.usage = usage
+                                    else:
+                                        chunk.usage = None
+
                                 data = chunk.model_dump_json(
                                     exclude_unset=True)
                                 yield f"data: {data}\n\n"
@@ -336,7 +355,19 @@ async def chat_completion_stream_generator(
                             model=model_name)
                         if (request.stream_options
                                 and request.stream_options.include_usage):
-                            chunk.usage = None
+                            if (request.stream_options.continuous_usage_stats):
+                                prompt_tokens = len(res.prompt_token_ids)
+                                completion_tokens = len(output.token_ids)
+                                usage = UsageInfo(
+                                    prompt_tokens=prompt_tokens,
+                                    completion_tokens=completion_tokens,
+                                    total_tokens=prompt_tokens +
+                                    completion_tokens,
+                                )
+                                chunk.usage = usage
+                            else:
+                                chunk.usage = None
+
                         data = chunk.model_dump_json(exclude_unset=True)
                         yield f"data: {data}\n\n"
                     else:
@@ -356,7 +387,18 @@ async def chat_completion_stream_generator(
                             model=model_name)
                         if (request.stream_options
                                 and request.stream_options.include_usage):
-                            chunk.usage = None
+                            if (request.stream_options.continuous_usage_stats):
+                                prompt_tokens = len(res.prompt_token_ids)
+                                completion_tokens = len(output.token_ids)
+                                usage = UsageInfo(
+                                    prompt_tokens=prompt_tokens,
+                                    completion_tokens=completion_tokens,
+                                    total_tokens=prompt_tokens +
+                                    completion_tokens,
+                                )
+                                chunk.usage = usage
+                            else:
+                                chunk.usage = None
                         data = chunk.model_dump_json(exclude_unset=True)
                         yield f"data: {data}\n\n"
                         finish_reason_sent[i] = True