[Front-end] microbatch tokenization (#19334)

Signed-off-by: zt2370 <ztang2370@gmail.com>

tests/entrypoints/openai/test_serving_chat.py

@@ -7,6 +7,8 @@ from dataclasses import dataclass, field
 from typing import Any, Optional
 from unittest.mock import MagicMock
 
+import pytest
+
 from vllm.config import MultiModalConfig
 from vllm.engine.multiprocessing.client import MQLLMEngineClient
 from vllm.entrypoints.openai.protocol import ChatCompletionRequest
@@ -73,7 +75,8 @@ def test_async_serving_chat_init():
     assert serving_completion.chat_template == CHAT_TEMPLATE
 
 
-def test_serving_chat_should_set_correct_max_tokens():
+@pytest.mark.asyncio
+async def test_serving_chat_should_set_correct_max_tokens():
     mock_engine = MagicMock(spec=MQLLMEngineClient)
     mock_engine.get_tokenizer.return_value = get_tokenizer(MODEL_NAME)
     mock_engine.errored = False
@@ -88,6 +91,7 @@ def test_serving_chat_should_set_correct_max_tokens():
                                      chat_template=CHAT_TEMPLATE,
                                      chat_template_content_format="auto",
                                      request_logger=None)
+
     req = ChatCompletionRequest(
         model=MODEL_NAME,
         messages=[{
@@ -98,13 +102,13 @@ def test_serving_chat_should_set_correct_max_tokens():
     )
 
     with suppress(Exception):
-        asyncio.run(serving_chat.create_chat_completion(req))
+        await serving_chat.create_chat_completion(req)
 
     assert mock_engine.generate.call_args.args[1].max_tokens == 93
 
     req.max_tokens = 10
     with suppress(Exception):
-        asyncio.run(serving_chat.create_chat_completion(req))
+        await serving_chat.create_chat_completion(req)
 
     assert mock_engine.generate.call_args.args[1].max_tokens == 10
 
@@ -143,7 +147,7 @@ def test_serving_chat_should_set_correct_max_tokens():
     )
 
     with suppress(Exception):
-        asyncio.run(serving_chat.create_chat_completion(req))
+        await serving_chat.create_chat_completion(req)
 
     assert mock_engine.generate.call_args.args[1].max_tokens == 10
 
@@ -151,7 +155,7 @@ def test_serving_chat_should_set_correct_max_tokens():
     req.max_tokens = 15
 
     with suppress(Exception):
-        asyncio.run(serving_chat.create_chat_completion(req))
+        await serving_chat.create_chat_completion(req)
 
     assert mock_engine.generate.call_args.args[1].max_tokens == 10
 
@@ -159,7 +163,7 @@ def test_serving_chat_should_set_correct_max_tokens():
     req.max_tokens = 5
 
     with suppress(Exception):
-        asyncio.run(serving_chat.create_chat_completion(req))
+        await serving_chat.create_chat_completion(req)
 
     assert mock_engine.generate.call_args.args[1].max_tokens == 5
 
@@ -198,7 +202,7 @@ def test_serving_chat_should_set_correct_max_tokens():
     )
 
     with suppress(Exception):
-        asyncio.run(serving_chat.create_chat_completion(req))
+        await serving_chat.create_chat_completion(req)
 
     assert mock_engine.generate.call_args.args[1].max_tokens == 93
 
@@ -206,7 +210,7 @@ def test_serving_chat_should_set_correct_max_tokens():
     req.max_tokens = 100
 
     with suppress(Exception):
-        asyncio.run(serving_chat.create_chat_completion(req))
+        await serving_chat.create_chat_completion(req)
 
     assert mock_engine.generate.call_args.args[1].max_tokens == 93
 
@@ -214,12 +218,13 @@ def test_serving_chat_should_set_correct_max_tokens():
     req.max_tokens = 5
 
     with suppress(Exception):
-        asyncio.run(serving_chat.create_chat_completion(req))
+        await serving_chat.create_chat_completion(req)
 
     assert mock_engine.generate.call_args.args[1].max_tokens == 5
 
 
-def test_serving_chat_could_load_correct_generation_config():
+@pytest.mark.asyncio
+async def test_serving_chat_could_load_correct_generation_config():
 
     mock_model_config = MockModelConfig()
     mock_model_config.diff_sampling_param = {
@@ -242,6 +247,7 @@ def test_serving_chat_could_load_correct_generation_config():
                                      chat_template=CHAT_TEMPLATE,
                                      chat_template_content_format="auto",
                                      request_logger=None)
+
     req = ChatCompletionRequest(
         model=MODEL_NAME,
         messages=[{
@@ -252,7 +258,7 @@ def test_serving_chat_could_load_correct_generation_config():
     )
 
     with suppress(Exception):
-        asyncio.run(serving_chat.create_chat_completion(req))
+        await serving_chat.create_chat_completion(req)
 
     assert mock_engine.generate.call_args.args[1].temperature == 0.5
     assert mock_engine.generate.call_args.args[1].repetition_penalty == 1.05
@@ -261,7 +267,7 @@ def test_serving_chat_could_load_correct_generation_config():
     req.temperature = 0.1
 
     with suppress(Exception):
-        asyncio.run(serving_chat.create_chat_completion(req))
+        await serving_chat.create_chat_completion(req)
 
     assert mock_engine.generate.call_args.args[1].temperature == 0.1
     assert mock_engine.generate.call_args.args[1].repetition_penalty == 1.05
@@ -270,13 +276,14 @@ def test_serving_chat_could_load_correct_generation_config():
     req.temperature = 0.0
 
     with suppress(Exception):
-        asyncio.run(serving_chat.create_chat_completion(req))
+        await serving_chat.create_chat_completion(req)
 
     assert mock_engine.generate.call_args.args[1].temperature == 0.0
     assert mock_engine.generate.call_args.args[1].repetition_penalty == 1.05
 
 
-def test_serving_chat_did_set_correct_cache_salt():
+@pytest.mark.asyncio
+async def test_serving_chat_did_set_correct_cache_salt():
     mock_model_config = MockModelConfig()
 
     mock_engine = MagicMock(spec=MQLLMEngineClient)
@@ -306,11 +313,11 @@ def test_serving_chat_did_set_correct_cache_salt():
 
     # By default cache_salt in the engine prompt is not set
     with suppress(Exception):
-        asyncio.run(serving_chat.create_chat_completion(req))
+        await serving_chat.create_chat_completion(req)
     assert "cache_salt" not in mock_engine.generate.call_args.args[0]
 
     # Test with certain cache_salt
     req.cache_salt = "test_salt"
     with suppress(Exception):
-        asyncio.run(serving_chat.create_chat_completion(req))
+        await serving_chat.create_chat_completion(req)
     assert mock_engine.generate.call_args.args[0]["cache_salt"] == "test_salt"

vllm/entrypoints/openai/serving_engine.py

 # SPDX-License-Identifier: Apache-2.0
 # SPDX-FileCopyrightText: Copyright contributors to the vLLM project
+import asyncio
 import base64
 import io
 import json
 import sys
 import time
-from collections.abc import (AsyncGenerator, Iterable, Iterator, Mapping,
-                             Sequence)
-from concurrent.futures.thread import ThreadPoolExecutor
+from collections.abc import AsyncGenerator, Iterable, Mapping, Sequence
+from concurrent.futures import ThreadPoolExecutor
 from http import HTTPStatus
 from typing import (Annotated, Any, Callable, ClassVar, Generic, Optional,
                     TypeVar, Union, cast, overload)
@@ -79,8 +79,8 @@ from vllm.sequence import Logprob, PromptLogprobs
 from vllm.tracing import (contains_trace_headers, extract_trace_headers,
                           log_tracing_disabled_warning)
 from vllm.transformers_utils.tokenizer import AnyTokenizer, MistralTokenizer
-from vllm.utils import (is_list_of, make_async, merge_async_iterators,
-                        random_uuid)
+from vllm.utils import (AsyncMicrobatchTokenizer, is_list_of,
+                        merge_async_iterators, random_uuid)
 
 logger = init_logger(__name__)
 
@@ -226,11 +226,19 @@ class OpenAIServing:
 
         self._tokenizer_executor = ThreadPoolExecutor(max_workers=1)
 
-        self._tokenize_prompt_input_async = make_async(
-            self._tokenize_prompt_input, executor=self._tokenizer_executor)
-        self._tokenize_prompt_input_or_inputs_async = make_async(
-            self._tokenize_prompt_input_or_inputs,
-            executor=self._tokenizer_executor)
+        self._async_tokenizer_pool: dict[AnyTokenizer,
+                                         AsyncMicrobatchTokenizer] = {}
+
+    def _get_async_tokenizer(self, tokenizer) -> AsyncMicrobatchTokenizer:
+        """
+        Return (and cache) an `AsyncMicrobatchTokenizer` bound to the 
+        given tokenizer.
+        """
+        async_tokenizer = self._async_tokenizer_pool.get(tokenizer)
+        if async_tokenizer is None:
+            async_tokenizer = AsyncMicrobatchTokenizer(tokenizer)
+            self._async_tokenizer_pool[tokenizer] = async_tokenizer
+        return async_tokenizer
 
     async def _preprocess(
         self,
@@ -467,7 +475,7 @@ class OpenAIServing:
         # if _check_model has been called earlier, this will be unreachable
         raise ValueError(f"The model `{request.model}` does not exist.")
 
-    def _normalize_prompt_text_to_input(
+    async def _normalize_prompt_text_to_input(
         self,
         request: AnyRequest,
         tokenizer: AnyTokenizer,
@@ -475,38 +483,44 @@ class OpenAIServing:
         truncate_prompt_tokens: Optional[Annotated[int, Field(ge=-1)]],
         add_special_tokens: bool,
     ) -> TextTokensPrompt:
+        async_tokenizer = self._get_async_tokenizer(tokenizer)
+
         if (self.model_config.encoder_config is not None
                 and self.model_config.encoder_config.get(
                     "do_lower_case", False)):
             prompt = prompt.lower()
 
         if truncate_prompt_tokens is None:
-            encoded = tokenizer(prompt, add_special_tokens=add_special_tokens)
+            encoded = await async_tokenizer(
+                prompt, add_special_tokens=add_special_tokens)
         elif truncate_prompt_tokens < 0:
             # Negative means we cap at the model's max length
-            encoded = tokenizer(prompt,
-                                add_special_tokens=add_special_tokens,
-                                truncation=True,
-                                max_length=self.max_model_len)
+            encoded = await async_tokenizer(
+                prompt,
+                add_special_tokens=add_special_tokens,
+                truncation=True,
+                max_length=self.max_model_len)
         else:
-            encoded = tokenizer(prompt,
-                                add_special_tokens=add_special_tokens,
-                                truncation=True,
-                                max_length=truncate_prompt_tokens)
+            encoded = await async_tokenizer(
+                prompt,
+                add_special_tokens=add_special_tokens,
+                truncation=True,
+                max_length=truncate_prompt_tokens)
 
         input_ids = encoded.input_ids
-
         input_text = prompt
 
         return self._validate_input(request, input_ids, input_text)
 
-    def _normalize_prompt_tokens_to_input(
+    async def _normalize_prompt_tokens_to_input(
         self,
         request: AnyRequest,
         tokenizer: AnyTokenizer,
         prompt_ids: list[int],
         truncate_prompt_tokens: Optional[Annotated[int, Field(ge=1)]],
     ) -> TextTokensPrompt:
+        async_tokenizer = self._get_async_tokenizer(tokenizer)
+
         if truncate_prompt_tokens is None:
             input_ids = prompt_ids
         elif truncate_prompt_tokens < 0:
@@ -514,7 +528,7 @@ class OpenAIServing:
         else:
             input_ids = prompt_ids[-truncate_prompt_tokens:]
 
-        input_text = tokenizer.decode(input_ids)
+        input_text = await async_tokenizer.decode(input_ids)
 
         return self._validate_input(request, input_ids, input_text)
 
@@ -578,7 +592,7 @@ class OpenAIServing:
 
         return TextTokensPrompt(prompt=input_text, prompt_token_ids=input_ids)
 
-    def _tokenize_prompt_input(
+    async def _tokenize_prompt_input_async(
         self,
         request: AnyRequest,
         tokenizer: AnyTokenizer,
@@ -591,23 +605,24 @@ class OpenAIServing:
         [`_tokenize_prompt_input_or_inputs`][vllm.entrypoints.openai.serving_engine.OpenAIServing._tokenize_prompt_input_or_inputs]
         that assumes single input.
         """
-        return next(
-            self._tokenize_prompt_inputs(
+        async for result in self._tokenize_prompt_inputs_async(
                 request,
                 tokenizer,
-                [prompt_input],
+            [prompt_input],
                 truncate_prompt_tokens=truncate_prompt_tokens,
                 add_special_tokens=add_special_tokens,
-            ))
+        ):
+            return result
+        raise ValueError("No results yielded from tokenization")
 
-    def _tokenize_prompt_inputs(
+    async def _tokenize_prompt_inputs_async(
         self,
         request: AnyRequest,
         tokenizer: AnyTokenizer,
         prompt_inputs: Iterable[Union[str, list[int]]],
         truncate_prompt_tokens: Optional[Annotated[int, Field(ge=-1)]] = None,
         add_special_tokens: bool = True,
-    ) -> Iterator[TextTokensPrompt]:
+    ) -> AsyncGenerator[TextTokensPrompt, None]:
         """
         A simpler implementation of
         [`_tokenize_prompt_input_or_inputs`][vllm.entrypoints.openai.serving_engine.OpenAIServing._tokenize_prompt_input_or_inputs]
@@ -615,7 +630,7 @@ class OpenAIServing:
         """
         for text in prompt_inputs:
             if isinstance(text, str):
-                yield self._normalize_prompt_text_to_input(
+                yield await self._normalize_prompt_text_to_input(
                     request,
                     tokenizer,
                     prompt=text,
@@ -623,14 +638,14 @@ class OpenAIServing:
                     add_special_tokens=add_special_tokens,
                 )
             else:
-                yield self._normalize_prompt_tokens_to_input(
+                yield await self._normalize_prompt_tokens_to_input(
                     request,
                     tokenizer,
                     prompt_ids=text,
                     truncate_prompt_tokens=truncate_prompt_tokens,
                 )
 
-    def _tokenize_prompt_input_or_inputs(
+    async def _tokenize_prompt_input_or_inputs_async(
         self,
         request: AnyRequest,
         tokenizer: AnyTokenizer,
@@ -664,21 +679,31 @@ class OpenAIServing:
         # VSCode Pyright extension should still work properly
         # "is False" is required for Pyright to perform type narrowing
         # See: https://github.com/microsoft/pyright/issues/7672
-        inputs_text.extend([
-            self._normalize_prompt_text_to_input(
-                request,
-                tokenizer,
-                prompt=prompt_input["content"],
-                truncate_prompt_tokens=truncate_prompt_tokens,
-                add_special_tokens=add_special_tokens)
-            if prompt_input["is_tokens"] is False else
-            self._normalize_prompt_tokens_to_input(
-                request,
-                tokenizer,
-                prompt_ids=prompt_input["content"],
-                truncate_prompt_tokens=truncate_prompt_tokens)
-            for prompt_input in parse_and_batch_prompt(input_or_inputs)
-        ])
+
+        # Parse and batch the input prompts
+        batch_inputs = parse_and_batch_prompt(input_or_inputs)
+
+        # Process each input in the batch concurrently
+        tasks = []
+        for prompt_input in batch_inputs:
+            if prompt_input["is_tokens"] is False:
+                task = self._normalize_prompt_text_to_input(
+                    request,
+                    tokenizer,
+                    prompt_input["content"],
+                    truncate_prompt_tokens=truncate_prompt_tokens,
+                    add_special_tokens=add_special_tokens)
+            else:
+                task = self._normalize_prompt_tokens_to_input(
+                    request,
+                    tokenizer,
+                    prompt_input["content"],
+                    truncate_prompt_tokens=truncate_prompt_tokens)
+            tasks.append(task)
+
+        # Wait for all tokenization tasks to complete
+        results = await asyncio.gather(*tasks)
+        inputs_text.extend(results)
 
         return inputs_text, inputs_embeds
 

vllm/utils/__init__.py

@@ -41,6 +41,7 @@ from collections import UserDict, defaultdict
 from collections.abc import (AsyncGenerator, Awaitable, Collection, Generator,
                              Hashable, Iterable, Iterator, KeysView, Mapping,
                              Sequence)
+from concurrent.futures import ThreadPoolExecutor
 from concurrent.futures.process import ProcessPoolExecutor
 from dataclasses import dataclass, field
 from functools import cache, lru_cache, partial, wraps
@@ -64,6 +65,7 @@ import zmq.asyncio
 from packaging import version
 from packaging.version import Version
 from torch.library import Library
+from transformers.tokenization_utils_base import BatchEncoding
 from typing_extensions import Never, ParamSpec, TypeIs, assert_never
 
 import vllm.envs as envs
@@ -507,6 +509,196 @@ def random_uuid() -> str:
     return str(uuid.uuid4().hex)
 
 
+class AsyncMicrobatchTokenizer:
+    """Asynchronous tokenizer with micro-batching.
+
+    Pulls pending encode/decode requests from a queue and batches them 
+    up to reduce overhead. A single-thread ThreadPoolExecutor is used 
+    so the event loop stays responsive.
+    """
+
+    def __init__(
+        self,
+        tokenizer,
+        max_batch_size: int = 32,
+        batch_wait_timeout_s: float = 0.002,
+    ) -> None:
+        self.tokenizer = tokenizer
+        self.max_batch_size = max_batch_size
+        self.batch_wait_timeout_s = batch_wait_timeout_s
+
+        self._loop = asyncio.get_running_loop()
+        self._queues: dict[tuple,
+                           asyncio.Queue[Union[tuple[str, dict,
+                                                     asyncio.Future],
+                                               tuple[list[int],
+                                                     asyncio.Future]]]] = {}
+        self._batcher_tasks: list[asyncio.Task] = []
+
+        # Single-thread executor for blocking tokenizer calls.
+        self._executor = ThreadPoolExecutor(max_workers=1)
+
+    # === Public async API ===
+    async def __call__(self, prompt, **kwargs):
+        result_future: asyncio.Future = self._loop.create_future()
+        key = self._queue_key("encode", kwargs)
+        queue = self._get_queue(self._loop, key)
+        await queue.put((prompt, kwargs, result_future))
+        return await result_future
+
+    async def decode(self, token_ids, **kwargs):
+        result_future: asyncio.Future = self._loop.create_future()
+        key = self._queue_key("decode", kwargs)
+        queue = self._get_queue(self._loop, key)
+        await queue.put((token_ids, result_future))
+        return await result_future
+
+    # === Internal helpers ===
+    def _get_queue(
+        self, loop: asyncio.AbstractEventLoop, key: tuple
+    ) -> asyncio.Queue[Union[tuple[str, dict, asyncio.Future], tuple[
+            list[int], asyncio.Future]]]:
+        """Get the request queue for the given operation key, creating a new
+        queue and batcher task if needed."""
+        queue = self._queues.get(key)
+        if queue is None:
+            self._queues[key] = queue = asyncio.Queue()
+            if key[0] == "encode":
+                can_batch = key[1] != "other"
+                coro = self._batch_encode_loop(queue, can_batch)
+            else:
+                assert key[0] == "decode", \
+                    f"Unknown operation type: {key[0]}."
+                coro = self._batch_decode_loop(queue)
+            self._batcher_tasks.append(loop.create_task(coro))
+        return queue
+
+    async def _batch_encode_loop(self, queue: asyncio.Queue, can_batch: bool):
+        """Batch incoming encode requests for efficiency."""
+        while True:
+            prompt, kwargs, result_future = await queue.get()
+            prompts = [prompt]
+            kwargs_list = [kwargs]
+            result_futures = [result_future]
+            deadline = self._loop.time() + self.batch_wait_timeout_s
+
+            while len(prompts) < self.max_batch_size:
+                timeout = deadline - self._loop.time()
+                if timeout <= 0:
+                    break
+                try:
+                    prompt, kwargs, result_future = await asyncio.wait_for(
+                        queue.get(), timeout)
+                    prompts.append(prompt)
+                    result_futures.append(result_future)
+                    if not can_batch:
+                        kwargs_list.append(kwargs)
+                except asyncio.TimeoutError:
+                    break
+
+            try:
+                # If every request uses identical kwargs we can run a single
+                # batched tokenizer call for a big speed-up.
+                if can_batch and len(prompts) > 1:
+                    encode_fn = partial(self.tokenizer, prompts, **kwargs)
+                    results = await self._loop.run_in_executor(
+                        self._executor, encode_fn)
+
+                    for i, fut in enumerate(result_futures):
+                        if not fut.done():
+                            data = {k: v[i] for k, v in results.items()}
+                            fut.set_result(BatchEncoding(data))
+                else:
+                    encode_fn = lambda prompts=prompts, kwargs=kwargs_list: [
+                        self.tokenizer(p, **kw)
+                        for p, kw in zip(prompts, kwargs)
+                    ]
+                    results = await self._loop.run_in_executor(
+                        self._executor, encode_fn)
+
+                    for fut, res in zip(result_futures, results):
+                        if not fut.done():
+                            fut.set_result(res)
+            except Exception as e:
+                for fut in result_futures:
+                    if not fut.done():
+                        fut.set_exception(e)
+
+    async def _batch_decode_loop(self, queue: asyncio.Queue):
+        """Batch incoming decode requests for efficiency."""
+        while True:
+            token_ids, result_future = await queue.get()
+            token_ids_list = [token_ids]
+            result_futures = [result_future]
+            deadline = self._loop.time() + self.batch_wait_timeout_s
+
+            while len(token_ids_list) < self.max_batch_size:
+                timeout = deadline - self._loop.time()
+                if timeout <= 0:
+                    break
+                try:
+                    token_ids, result_future = await asyncio.wait_for(
+                        queue.get(), timeout)
+                    token_ids_list.append(token_ids)
+                    result_futures.append(result_future)
+                except asyncio.TimeoutError:
+                    break
+
+            try:
+                # Perform a single batched decode call for all requests
+                results = await self._loop.run_in_executor(
+                    self._executor, self.tokenizer.batch_decode,
+                    token_ids_list)
+                for fut, res in zip(result_futures, results):
+                    if not fut.done():
+                        fut.set_result(res)
+            except Exception as e:
+                for fut in result_futures:
+                    if not fut.done():
+                        fut.set_exception(e)
+
+    def _queue_key(self, op: str, kwargs: dict) -> tuple:
+        """
+        Return a normalized key describing operation + kwargs.
+        
+        - `add_special_tokens`: {True/False}
+        - `truncation`: {True/False}
+          - If `truncation` is False (`max_length` is None), 
+            returns a key for a can_batch queue.
+          - If `truncation` is True and `max_length` is None or equals
+            `tokenizer.model_max_length`, returns a key for a can_batch queue.
+          - Otherwise, returns a key for a cannot_batch queue.
+        
+        Examples:
+          - Decode: ("decode",)
+          - Encode typical: 
+            ("encode", add_special_tokens, bool_truncation, max_length_label)
+          - Fallback: ("encode", "other")
+        """
+
+        if op == "decode":
+            return ("decode", )
+
+        add_special_tokens = kwargs.get("add_special_tokens", True)
+        truncation = kwargs.get("truncation", False)
+        max_length = kwargs.get("max_length")
+
+        if not truncation:
+            return ("encode", add_special_tokens, False, None)
+
+        model_max = getattr(self.tokenizer, "model_max_length", None)
+        if max_length is None or (model_max is not None
+                                  and max_length == model_max):
+            return ("encode", add_special_tokens, True, "model_max")
+
+        return ("encode", "other")
+
+    def __del__(self):
+        for task in self._batcher_tasks:
+            if not task.done():
+                task.cancel()
+
+
 def make_async(
     func: Callable[P, T],
     executor: Optional[concurrent.futures.Executor] = None