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[Bug]: AsyncLLMEngine stuck in V1 #19892

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@lullabies777

Description

@lullabies777

Your current environment

INFO 06-20 10:55:55 [init.py:244] Automatically detected platform cuda.
Collecting environment information...

    System Info

==============================
OS : Ubuntu 22.04.5 LTS (x86_64)
GCC version : (Ubuntu 11.4.0-1ubuntu1~22.04) 11.4.0
Clang version : Could not collect
CMake version : version 4.0.2
Libc version : glibc-2.35

==============================
PyTorch Info

PyTorch version : 2.7.0+cu126
Is debug build : False
CUDA used to build PyTorch : 12.6
ROCM used to build PyTorch : N/A

==============================
Python Environment

Python version : 3.12.10 | packaged by conda-forge | (main, Apr 10 2025, 22:21:13) [GCC 13.3.0] (64-bit runtime)
Python platform : Linux-5.10.134-16.1.al8.x86_64-x86_64-with-glibc2.35

==============================
CUDA / GPU Info

Is CUDA available : True
CUDA runtime version : Could not collect
CUDA_MODULE_LOADING set to : LAZY
GPU models and configuration : GPU 0: NVIDIA H20
Nvidia driver version : 550.54.15
cuDNN version : Could not collect
HIP runtime version : N/A
MIOpen runtime version : N/A
Is XNNPACK available : True

==============================
CPU Info

架构: x86_64
CPU 运行模式: 32-bit, 64-bit
Address sizes: 52 bits physical, 57 bits virtual
字节序: Little Endian
CPU: 24
在线 CPU 列表: 0-23
厂商 ID: GenuineIntel
型号名称: Intel(R) Xeon(R) Platinum 8469C
CPU 系列: 6
型号: 143
每个核的线程数: 2
每个座的核数: 12
座: 1
步进: 8
CPU 最大 MHz: 3800.0000
CPU 最小 MHz: 800.0000
BogoMIPS: 5200.00
标记: fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ss ht syscall nx pdpe1gb rdtscp lm constant_tsc rep_good nopl xtopology nonstop_tsc cpuid aperfmperf tsc_known_freq pni pclmulqdq monitor ssse3 fma cx16 pdcm pcid sse4_1 sse4_2 x2apic movbe popcnt aes xsave avx f16c rdrand hypervisor lahf_lm abm 3dnowprefetch cpuid_fault invpcid_single ibrs_enhanced fsgsbase tsc_adjust bmi1 hle avx2 smep bmi2 erms invpcid rtm avx512f avx512dq rdseed adx smap avx512ifma clflushopt clwb avx512cd sha_ni avx512bw avx512vl xsaveopt xsavec xgetbv1 xsaves avx_vnni avx512_bf16 wbnoinvd ida arat hwp hwp_notify hwp_act_window hwp_epp hwp_pkg_req avx512vbmi umip pku ospke waitpkg avx512_vbmi2 gfni vaes vpclmulqdq avx512_vnni avx512_bitalg avx512_vpopcntdq rdpid bus_lock_detect cldemote movdiri movdir64b enqcmd fsrm uintr md_clear serialize tsxldtrk amx_bf16 avx512_fp16 amx_tile amx_int8 arch_capabilities
超管理器厂商: KVM
虚拟化类型: 完全
L1d 缓存: 576 KiB (12 instances)
L1i 缓存: 384 KiB (12 instances)
L2 缓存: 24 MiB (12 instances)
L3 缓存: 97.5 MiB (1 instance)
NUMA 节点: 1
NUMA 节点0 CPU: 0-23
Vulnerability Itlb multihit: Not affected
Vulnerability L1tf: Not affected
Vulnerability Mds: Not affected
Vulnerability Meltdown: Not affected
Vulnerability Mmio stale data: Not affected
Vulnerability Retbleed: Not affected
Vulnerability Spec store bypass: Vulnerable
Vulnerability Spectre v1: Mitigation; usercopy/swapgs barriers and __user pointer sanitization
Vulnerability Spectre v2: Mitigation; Enhanced IBRS, RSB filling, PBRSB-eIBRS SW sequence
Vulnerability Srbds: Not affected
Vulnerability Tsx async abort: Not affected

==============================
Versions of relevant libraries

[pip3] numpy==1.26.4
[pip3] nvidia-cublas-cu12==12.6.4.1
[pip3] nvidia-cuda-cupti-cu12==12.6.80
[pip3] nvidia-cuda-nvrtc-cu12==12.6.77
[pip3] nvidia-cuda-runtime-cu12==12.6.77
[pip3] nvidia-cudnn-cu12==9.5.1.17
[pip3] nvidia-cufft-cu12==11.3.0.4
[pip3] nvidia-cufile-cu12==1.11.1.6
[pip3] nvidia-curand-cu12==10.3.7.77
[pip3] nvidia-cusolver-cu12==11.7.1.2
[pip3] nvidia-cusparse-cu12==12.5.4.2
[pip3] nvidia-cusparselt-cu12==0.6.3
[pip3] nvidia-ml-py==12.575.51
[pip3] nvidia-nccl-cu12==2.26.2
[pip3] nvidia-nvjitlink-cu12==12.6.85
[pip3] nvidia-nvtx-cu12==12.6.77
[pip3] pytorch-lightning==2.5.1.post0
[pip3] pyzmq==26.2.0
[pip3] torch==2.7.0
[pip3] torchaudio==2.7.0
[pip3] torchmetrics==0.10.3
[pip3] torchvision==0.22.0
[pip3] transformers==4.52.4
[pip3] triton==3.3.0
[conda] numpy 1.26.4 pypi_0 pypi
[conda] nvidia-cublas-cu12 12.6.4.1 pypi_0 pypi
[conda] nvidia-cuda-cupti-cu12 12.6.80 pypi_0 pypi
[conda] nvidia-cuda-nvrtc-cu12 12.6.77 pypi_0 pypi
[conda] nvidia-cuda-runtime-cu12 12.6.77 pypi_0 pypi
[conda] nvidia-cudnn-cu12 9.5.1.17 pypi_0 pypi
[conda] nvidia-cufft-cu12 11.3.0.4 pypi_0 pypi
[conda] nvidia-cufile-cu12 1.11.1.6 pypi_0 pypi
[conda] nvidia-curand-cu12 10.3.7.77 pypi_0 pypi
[conda] nvidia-cusolver-cu12 11.7.1.2 pypi_0 pypi
[conda] nvidia-cusparse-cu12 12.5.4.2 pypi_0 pypi
[conda] nvidia-cusparselt-cu12 0.6.3 pypi_0 pypi
[conda] nvidia-ml-py 12.575.51 pypi_0 pypi
[conda] nvidia-nccl-cu12 2.26.2 pypi_0 pypi
[conda] nvidia-nvjitlink-cu12 12.6.85 pypi_0 pypi
[conda] nvidia-nvtx-cu12 12.6.77 pypi_0 pypi
[conda] pytorch-lightning 2.5.1.post0 pypi_0 pypi
[conda] pyzmq 26.4.0 pypi_0 pypi
[conda] torch 2.7.0 pypi_0 pypi
[conda] torchaudio 2.7.0 pypi_0 pypi
[conda] torchmetrics 0.10.3 pypi_0 pypi
[conda] torchvision 0.22.0 pypi_0 pypi
[conda] transformers 4.52.4 pypi_0 pypi
[conda] triton 3.3.0 pypi_0 pypi

==============================
vLLM Info

ROCM Version : Could not collect
Neuron SDK Version : N/A
vLLM Version : 0.9.1
vLLM Build Flags:
CUDA Archs: Not Set; ROCm: Disabled; Neuron: Disabled
GPU Topology:
GPU0 CPU Affinity NUMA Affinity GPU NUMA ID
GPU0 X 0-23 0 N/A

Legend:

X = Self
SYS = Connection traversing PCIe as well as the SMP interconnect between NUMA nodes (e.g., QPI/UPI)
NODE = Connection traversing PCIe as well as the interconnect between PCIe Host Bridges within a NUMA node
PHB = Connection traversing PCIe as well as a PCIe Host Bridge (typically the CPU)
PXB = Connection traversing multiple PCIe bridges (without traversing the PCIe Host Bridge)
PIX = Connection traversing at most a single PCIe bridge
NV# = Connection traversing a bonded set of # NVLinks

==============================
Environment Variables

NCCL_CUMEM_ENABLE=0
PYTORCH_NVML_BASED_CUDA_CHECK=1
TORCHINDUCTOR_COMPILE_THREADS=1
CUDA_MODULE_LOADING=LAZY

🐛 Describe the bug

AsyncLLMEngine stucks in V1, but works in V0.

predict.py

from vllm import SamplingParams
from vllm.lora.request import LoRARequest
import time 
# from loguru import logger
import torch

async def async_gen(model, text, uid):
    results_generator = model.generate(
            text,
            SamplingParams(
                n=1,  # Number of output sequences to return for each prompt.
                top_k=1,  # Float that controls the cumulative probability of the top tokens to consider.
                temperature=0,  # randomness of the sampling
                seed=777, # Seed for reprodicibility
                skip_special_tokens=False,  # Whether to skip special tokens in the output.
                max_tokens=1,  # Maximum number of tokens to generate per output sequence.
                ],
                logprobs=25
            ),
            uid,
            lora_request=LoRARequest("clue_type", 1, "./checkpoint-300")
        )
    
    final_output = None

    async for request_output in results_generator:
        final_output = request_output
    
    return final_output

async def predict_clue_type(model, tokenizer, inputs, uid):
    text = inputs["text"]
    
    responses = await async_gen(model, text, uid)
  
    
    return {"success": True, "prob": prob, "message": ""}

main.py

@app.post("/v1/models/{model_name}:predict")
async def predict(request: Item): # async def predict(request: Item):
    inputs = request.dict()
    st = time.time()
    md5 = hashlib.md5()
    md5.update(json.dumps(inputs, indent=4, ensure_ascii=False).encode("utf-8"))
    uid = md5.hexdigest()
    random_uid = uuid.uuid4()
    
    
    try:
        res = await predict_clue_type(engine, tokenizer, inputs, random_uid)
    except:
        error_mess = json.dumps(
            { "uid": uid,
                "input": inputs,
                "error": traceback.format_exc()
            }, indent = 4)
        
        #logger.error(error_mess)
        print(error_mess)
        res = {"success": False, "message": error_mess, "prob": -1}
    finally:
        et = time.time()
        cost_time = round(et - st, 1)
        #logger.info(f"Predict {uid} costs : {cost_time}s")
        print(f"Predict {uid} costs : {cost_time}s")
    return res



@app.on_event("startup")
async def startup_event():
    st = time.time()
    global tokenizer, engine
    tokenizer = AutoTokenizer.from_pretrained('./Qwen3-8B')

    engine = AsyncLLMEngine.from_engine_args(
            AsyncEngineArgs(
                    model="./Qwen3-8B",
                    tensor_parallel_size=1,
                    gpu_memory_utilization=0.5, 
                    trust_remote_code=True,
                    dtype="bfloat16" if is_bfloat16_supported() else "float16", 
                    enforce_eager=True,
                    max_model_len=4096,
                    disable_log_stats=True,
                    max_logprobs=25,
                    enable_lora=True,
                    max_lora_rank=64,
                    disable_log_requests=True
            )
        )
    et = time.time()
    cost_time = round(et - st, 1)
    print(f"Initalization costs : {cost_time}s")

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