Closed
Description
🐛 Describe the bug
I'm trying to use Elastic to handle nodes joining or leaving during training. My setup runs two EC2 instances (Ubuntu 24.04, g4dn.xlarge, NVIDIA Tesla T4, driver 550, PyTorch in a venv). My script is minimal, reproducible and attached here. It's a simplified version of this example. Each node runs:
torchrun \
--nproc-per-node=1 \
--max-restarts=3 \
--node-rank=0|1 \
--nnodes=1:2 \
--rdzv-id=001 \
--rdzv-backend=c10d \
--rdzv-endpoint=<IP> \
script.py 50 10 --batch_size 32Each node launches one agent, which manages one worker. The node with --node-rank=0 acts as the rendezvous server. If I kill its process, the training crashes as expected since it's a single point of failure. However, the problem is with the other node. Killing its worker results in correct behavior as the agent restarts it up to the value of --max-restarts. But when I kill its agent, the training crashes instead of continuing with the rendezvous node only. The full traceback of the exception is included below.
On the rendezvous node:
[rank1]:[E409 07:28:50.917104566 ProcessGroupNCCL.cpp:552] [Rank 1] Collective WorkNCCL(SeqNum=632, OpType=ALLREDUCE, NumelIn=1, NumelOut=1, Timeout(ms)=600000) raised the following async exception: NCCL error: remote process exited or there was a network error, NCCL version 2.21.5
ncclRemoteError: A call failed possibly due to a network error or a remote process exiting prematurely.
Last error:
socketProgress: Connection closed by remote peer ip-172-31-36-217.eu-north-1.compute.internal<59116>
Exception raised from checkForNCCLErrorsInternal at /pytorch/torch/csrc/distributed/c10d/ProcessGroupNCCL.cpp:2363 (most recent call first):
frame #0: c10::Error::Error(c10::SourceLocation, std::string) + 0x96 (0x7861000c31b6 in /home/ubuntu/prototype-venv/lib/python3.12/site-packages/torch/lib/libc10.so)
frame #1: c10d::ProcessGroupNCCL::checkForNCCLErrorsInternal(std::shared_ptr<c10d::NCCLComm>&) + 0x220 (0x7860ad5f61c0 in /home/ubuntu/prototype-venv/lib/python3.12/site-packages/torch/lib/libtorch_cuda.so)
frame #2: c10d::ProcessGroupNCCL::WorkNCCL::checkAndSetException() + 0x7b (0x7860ad5fe64b in /home/ubuntu/prototype-venv/lib/python3.12/site-packages/torch/lib/libtorch_cuda.so)
frame #3: c10d::ProcessGroupNCCL::watchdogHandler() + 0x650 (0x7860ad600590 in /home/ubuntu/prototype-venv/lib/python3.12/site-packages/torch/lib/libtorch_cuda.so)
frame #4: c10d::ProcessGroupNCCL::ncclCommWatchdog() + 0x14d (0x7860ad6016ed in /home/ubuntu/prototype-venv/lib/python3.12/site-packages/torch/lib/libtorch_cuda.so)
frame #5: <unknown function> + 0x145c0 (0x78610022e5c0 in /home/ubuntu/prototype-venv/lib/python3.12/site-packages/torch/lib/libtorch.so)
frame #6: <unknown function> + 0x9caa4 (0x786100c9caa4 in /lib/x86_64-linux-gnu/libc.so.6)
frame #7: <unknown function> + 0x129c3c (0x786100d29c3c in /lib/x86_64-linux-gnu/libc.so.6)
[rank1]:[E409 07:28:50.919638087 ProcessGroupNCCL.cpp:2168] [PG ID 0 PG GUID 0(default_pg) Rank 1] failure detected by watchdog at work sequence id: 632 PG status: last enqueued work: 632, last completed work: 631
[rank1]:[E409 07:28:50.919656087 ProcessGroupNCCL.cpp:667] Stack trace of the failed collective not found, potentially because FlightRecorder is disabled. You can enable it by setting TORCH_NCCL_TRACE_BUFFER_SIZE to a non-zero value.
Started epoch 19
[rank1]:[E409 07:28:50.740369821 ProcessGroupNCCL.cpp:681] [Rank 1] Some NCCL operations have failed or timed out. Due to the asynchronous nature of CUDA kernels, subsequent GPU operations might run on corrupted/incomplete data.
[rank1]:[E409 07:28:50.740390368 ProcessGroupNCCL.cpp:695] [Rank 1] To avoid data inconsistency, we are taking the entire process down.
[rank1]:[E409 07:28:50.740431045 ProcessGroupNCCL.cpp:1895] [PG ID 0 PG GUID 0(default_pg) Rank 1] Process group watchdog thread terminated with exception: NCCL error: remote process exited or there was a network error, NCCL version 2.21.5
ncclRemoteError: A call failed possibly due to a network error or a remote process exiting prematurely.
Last error:
socketProgress: Connection closed by remote peer ip-172-31-36-217.eu-north-1.compute.internal<59116>
Exception raised from checkForNCCLErrorsInternal at /pytorch/torch/csrc/distributed/c10d/ProcessGroupNCCL.cpp:2363 (most recent call first):
frame #0: c10::Error::Error(c10::SourceLocation, std::string) + 0x96 (0x7861000c31b6 in /home/ubuntu/prototype-venv/lib/python3.12/site-packages/torch/lib/libc10.so)
frame #1: c10d::ProcessGroupNCCL::checkForNCCLErrorsInternal(std::shared_ptr<c10d::NCCLComm>&) + 0x220 (0x7860ad5f61c0 in /home/ubuntu/prototype-venv/lib/python3.12/site-packages/torch/lib/libtorch_cuda.so)
frame #2: c10d::ProcessGroupNCCL::WorkNCCL::checkAndSetException() + 0x7b (0x7860ad5fe64b in /home/ubuntu/prototype-venv/lib/python3.12/site-packages/torch/lib/libtorch_cuda.so)
frame #3: c10d::ProcessGroupNCCL::watchdogHandler() + 0x650 (0x7860ad600590 in /home/ubuntu/prototype-venv/lib/python3.12/site-packages/torch/lib/libtorch_cuda.so)
frame #4: c10d::ProcessGroupNCCL::ncclCommWatchdog() + 0x14d (0x7860ad6016ed in /home/ubuntu/prototype-venv/lib/python3.12/site-packages/torch/lib/libtorch_cuda.so)
frame #5: <unknown function> + 0x145c0 (0x78610022e5c0 in /home/ubuntu/prototype-venv/lib/python3.12/site-packages/torch/lib/libtorch.so)
frame #6: <unknown function> + 0x9caa4 (0x786100c9caa4 in /lib/x86_64-linux-gnu/libc.so.6)
frame #7: <unknown function> + 0x129c3c (0x786100d29c3c in /lib/x86_64-linux-gnu/libc.so.6)
terminate called after throwing an instance of 'c10::DistBackendError'
what(): [PG ID 0 PG GUID 0(default_pg) Rank 1] Process group watchdog thread terminated with exception: NCCL error: remote process exited or there was a network error, NCCL version 2.21.5
ncclRemoteError: A call failed possibly due to a network error or a remote process exiting prematurely.
Last error:
socketProgress: Connection closed by remote peer ip-172-31-36-217.eu-north-1.compute.internal<59116>
Exception raised from checkForNCCLErrorsInternal at /pytorch/torch/csrc/distributed/c10d/ProcessGroupNCCL.cpp:2363 (most recent call first):
frame #0: c10::Error::Error(c10::SourceLocation, std::string) + 0x96 (0x7861000c31b6 in /home/ubuntu/prototype-venv/lib/python3.12/site-packages/torch/lib/libc10.so)
frame #1: c10d::ProcessGroupNCCL::checkForNCCLErrorsInternal(std::shared_ptr<c10d::NCCLComm>&) + 0x220 (0x7860ad5f61c0 in /home/ubuntu/prototype-venv/lib/python3.12/site-packages/torch/lib/libtorch_cuda.so)
frame #2: c10d::ProcessGroupNCCL::WorkNCCL::checkAndSetException() + 0x7b (0x7860ad5fe64b in /home/ubuntu/prototype-venv/lib/python3.12/site-packages/torch/lib/libtorch_cuda.so)
frame #3: c10d::ProcessGroupNCCL::watchdogHandler() + 0x650 (0x7860ad600590 in /home/ubuntu/prototype-venv/lib/python3.12/site-packages/torch/lib/libtorch_cuda.so)
frame #4: c10d::ProcessGroupNCCL::ncclCommWatchdog() + 0x14d (0x7860ad6016ed in /home/ubuntu/prototype-venv/lib/python3.12/site-packages/torch/lib/libtorch_cuda.so)
frame #5: <unknown function> + 0x145c0 (0x78610022e5c0 in /home/ubuntu/prototype-venv/lib/python3.12/site-packages/torch/lib/libtorch.so)
frame #6: <unknown function> + 0x9caa4 (0x786100c9caa4 in /lib/x86_64-linux-gnu/libc.so.6)
frame #7: <unknown function> + 0x129c3c (0x786100d29c3c in /lib/x86_64-linux-gnu/libc.so.6)
Exception raised from ncclCommWatchdog at /pytorch/torch/csrc/distributed/c10d/ProcessGroupNCCL.cpp:1901 (most recent call first):
frame #0: c10::Error::Error(c10::SourceLocation, std::string) + 0x96 (0x7861000c31b6 in /home/ubuntu/prototype-venv/lib/python3.12/site-packages/torch/lib/libc10.so)
frame #1: <unknown function> + 0xe5c6fc (0x7860ad25c6fc in /home/ubuntu/prototype-venv/lib/python3.12/site-packages/torch/lib/libtorch_cuda.so)
frame #2: <unknown function> + 0x145c0 (0x78610022e5c0 in /home/ubuntu/prototype-venv/lib/python3.12/site-packages/torch/lib/libtorch.so)
frame #3: <unknown function> + 0x9caa4 (0x786100c9caa4 in /lib/x86_64-linux-gnu/libc.so.6)
frame #4: <unknown function> + 0x129c3c (0x786100d29c3c in /lib/x86_64-linux-gnu/libc.so.6)
E0409 07:28:52.647000 1312 torch/distributed/elastic/multiprocessing/api.py:869] failed (exitcode: -6) local_rank: 0 (pid: 1318) of binary: /home/ubuntu/prototype-venv/bin/python3
Traceback (most recent call last):
File "/home/ubuntu/prototype-venv/bin/torchrun", line 8, in <module>
sys.exit(main())
^^^^^^
File "/home/ubuntu/prototype-venv/lib/python3.12/site-packages/torch/distributed/elastic/multiprocessing/errors/__init__.py", line 355, in wrapper
return f(*args, **kwargs)
^^^^^^^^^^^^^^^^^^
File "/home/ubuntu/prototype-venv/lib/python3.12/site-packages/torch/distributed/run.py", line 918, in main
run(args)
File "/home/ubuntu/prototype-venv/lib/python3.12/site-packages/torch/distributed/run.py", line 909, in run
elastic_launch(
File "/home/ubuntu/prototype-venv/lib/python3.12/site-packages/torch/distributed/launcher/api.py", line 138, in __call__
return launch_agent(self._config, self._entrypoint, list(args))
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/ubuntu/prototype-venv/lib/python3.12/site-packages/torch/distributed/launcher/api.py", line 260, in launch_agent
result = agent.run()
^^^^^^^^^^^
File "/home/ubuntu/prototype-venv/lib/python3.12/site-packages/torch/distributed/elastic/metrics/api.py", line 137, in wrapper
result = f(*args, **kwargs)
^^^^^^^^^^^^^^^^^^
File "/home/ubuntu/prototype-venv/lib/python3.12/site-packages/torch/distributed/elastic/agent/server/api.py", line 711, in run
result = self._invoke_run(role)
^^^^^^^^^^^^^^^^^^^^^^
File "/home/ubuntu/prototype-venv/lib/python3.12/site-packages/torch/distributed/elastic/agent/server/api.py", line 899, in _invoke_run
self._restart_workers(self._worker_group)
File "/home/ubuntu/prototype-venv/lib/python3.12/site-packages/torch/distributed/elastic/metrics/api.py", line 137, in wrapper
result = f(*args, **kwargs)
^^^^^^^^^^^^^^^^^^
File "/home/ubuntu/prototype-venv/lib/python3.12/site-packages/torch/distributed/elastic/agent/server/api.py", line 702, in _restart_workers
self._initialize_workers(worker_group)
File "/home/ubuntu/prototype-venv/lib/python3.12/site-packages/torch/distributed/elastic/metrics/api.py", line 137, in wrapper
result = f(*args, **kwargs)
^^^^^^^^^^^^^^^^^^
File "/home/ubuntu/prototype-venv/lib/python3.12/site-packages/torch/distributed/elastic/agent/server/api.py", line 683, in _initialize_workers
self._rendezvous(worker_group)
File "/home/ubuntu/prototype-venv/lib/python3.12/site-packages/torch/distributed/elastic/metrics/api.py", line 137, in wrapper
result = f(*args, **kwargs)
^^^^^^^^^^^^^^^^^^
File "/home/ubuntu/prototype-venv/lib/python3.12/site-packages/torch/distributed/elastic/agent/server/api.py", line 500, in _rendezvous
rdzv_info = spec.rdzv_handler.next_rendezvous()
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/ubuntu/prototype-venv/lib/python3.12/site-packages/torch/distributed/elastic/rendezvous/dynamic_rendezvous.py", line 1162, in next_rendezvous
self._op_executor.run(join_op, deadline, self._get_deadline)
File "/home/ubuntu/prototype-venv/lib/python3.12/site-packages/torch/distributed/elastic/rendezvous/dynamic_rendezvous.py", line 676, in run
raise RendezvousClosedError
torch.distributed.elastic.rendezvous.api.RendezvousClosedError
On the other node:
W0409 07:28:49.530000 1359 torch/distributed/elastic/agent/server/api.py:719] Received 15 death signal, shutting down workers
W0409 07:28:49.531000 1359 torch/distributed/elastic/multiprocessing/api.py:897] Sending process 1365 closing signal SIGTERM
Traceback (most recent call last):
File "/home/ubuntu/prototype-venv/bin/torchrun", line 8, in <module>
sys.exit(main())
^^^^^^
File "/home/ubuntu/prototype-venv/lib/python3.12/site-packages/torch/distributed/elastic/multiprocessing/errors/__init__.py", line 355, in wrapper
return f(*args, **kwargs)
^^^^^^^^^^^^^^^^^^
File "/home/ubuntu/prototype-venv/lib/python3.12/site-packages/torch/distributed/run.py", line 918, in main
run(args)
File "/home/ubuntu/prototype-venv/lib/python3.12/site-packages/torch/distributed/run.py", line 909, in run
elastic_launch(
File "/home/ubuntu/prototype-venv/lib/python3.12/site-packages/torch/distributed/launcher/api.py", line 138, in __call__
return launch_agent(self._config, self._entrypoint, list(args))
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/ubuntu/prototype-venv/lib/python3.12/site-packages/torch/distributed/launcher/api.py", line 260, in launch_agent
result = agent.run()
^^^^^^^^^^^
File "/home/ubuntu/prototype-venv/lib/python3.12/site-packages/torch/distributed/elastic/metrics/api.py", line 137, in wrapper
result = f(*args, **kwargs)
^^^^^^^^^^^^^^^^^^
File "/home/ubuntu/prototype-venv/lib/python3.12/site-packages/torch/distributed/elastic/agent/server/api.py", line 711, in run
result = self._invoke_run(role)
^^^^^^^^^^^^^^^^^^^^^^
File "/home/ubuntu/prototype-venv/lib/python3.12/site-packages/torch/distributed/elastic/agent/server/api.py", line 870, in _invoke_run
time.sleep(monitor_interval)
File "/home/ubuntu/prototype-venv/lib/python3.12/site-packages/torch/distributed/elastic/multiprocessing/api.py", line 84, in _terminate_process_handler
raise SignalException(f"Process {os.getpid()} got signal: {sigval}", sigval=sigval)
torch.distributed.elastic.multiprocessing.api.SignalException: Process 1359 got signal: 15
This happens regardless of whether
67E6
I use CTRL-C or kill <PID>. I’ve reviewed several related issues and discussions, like 67616, 67742, 147064 and this post. None of them address this scenario. Let me know if this behavior is expected or if I’m missing something. I’m happy to provide more details if needed.
Versions
PyTorch version: 2.6.0+cu124
Is debug build: False
CUDA used to build PyTorch: 12.4
ROCM used to build PyTorch: N/A
OS: Ubuntu 24.04.2 LTS (x86_64)
GCC version: (Ubuntu 13.3.0-6ubuntu2~24.04) 13.3.0
Clang version: Could not collect
CMake version: Could not collect
Libc version: glibc-2.39
Python version: 3.12.3 (main, Feb 4 2025, 14:48:35) [GCC 13.3.0] (64-bit runtime)
Python platform: Linux-6.8.0-1026-aws-x86_64-with-glibc2.39
Is CUDA available: True
CUDA runtime version: Could not collect
CUDA_MODULE_LOADING set to: LAZY
GPU models and configuration: GPU 0: Tesla T4
Nvidia driver version: 550.144.03
cuDNN version: Could not collect
HIP runtime version: N/A
MIOpen runtime version: N/A
Is XNNPACK available: True
CPU:
Architecture: x86_64
CPU op-mode(s): 32-bit, 64-bit
Address sizes: 46 bits physical, 48 bits virtual
Byte Order: Little Endian
CPU(s): 4
On-line CPU(s) list: 0-3
Vendor ID: GenuineIntel
Model name: Intel(R) Xeon(R) Platinum 8259CL CPU @ 2.50GHz
CPU family: 6
Model: 85
Thread(s) per core: 2
Core(s) per socket: 2
Socket(s): 1
Stepping: 7
BogoMIPS: 4999.99
Flags: 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 ssse3 fma cx16 pcid sse4_1 sse4_2 x2apic movbe popcnt tsc_deadline_timer aes xsave avx f16c rdrand hypervisor lahf_lm abm 3dnowprefetch pti fsgsbase tsc_adjust bmi1 avx2 smep bmi2 erms invpcid mpx avx512f avx512dq rdseed adx smap clflushopt clwb avx512cd avx512bw avx512vl xsaveopt xsavec xgetbv1 xsaves ida arat pku ospke avx512_vnni
Hypervisor vendor: KVM
Virtualization type: full
L1d cache: 64 KiB (2 instances)
L1i cache: 64 KiB (2 instances)
L2 cache: 2 MiB (2 instances)
L3 cache: 35.8 MiB (1 instance)
NUMA node(s): 1
NUMA node0 CPU(s): 0-3
Vulnerability Gather data sampling: Unknown: Dependent on hypervisor status
Vulnerability Itlb multihit: KVM: Mitigation: VMX unsupported
Vulnerability L1tf: Mitigation; PTE Inversion
Vulnerability Mds: Vulnerable: Clear CPU buffers attempted, no microcode; SMT Host state unknown
Vulnerability Meltdown: Mitigation; PTI
Vulnerability Mmio stale data: Vulnerable: Clear CPU buffers attempted, no microcode; SMT Host state unknown
Vulnerability Reg file data sampling: Not affected
Vulnerability Retbleed: Vulnerable
Vulnerability Spec rstack overflow: Not affected
Vulnerability Spec store bypass: Vulnerable
Vulnerability Spectre v1: Mitigation; usercopy/swapgs barriers and __user pointer sanitization
Vulnerability Spectre v2: Mitigation; Retpolines; STIBP disabled; RSB filling; PBRSB-eIBRS Not affected; BHI Retpoline
Vulnerability Srbds: Not affected
Vulnerability Tsx async abort: Not affected
Versions of relevant libraries:
[pip3] numpy==2.2.4
[pip3] nvidia-cublas-cu12==12.4.5.8
[pip3] nvidia-cuda-cupti-cu12==12.4.127
[pip3] nvidia-cuda-nvrtc-cu12==12.4.127
[pip3] nvidia-cuda-runtime-cu12==12.4.127
[pip3] nvidia-cudnn-cu12==9.1.0.70
[pip3] nvidia-cufft-cu12==11.2.1.3
[pip3] nvidia-curand-cu12==10.3.5.147
[pip3] nvidia-cusolver-cu12==11.6.1.9
[pip3] nvidia-cusparse-cu12==12.3.1.170
[pip3] nvidia-cusparselt-cu12==0.6.2
[pip3] nvidia-nccl-cu12==2.21.5
[pip3] nvidia-nvjitlink-cu12==12.4.127
[pip3] nvidia-nvtx-cu12==12.4.127
[pip3] torch==2.6.0
[pip3] torchaudio==2.6.0
[pip3] torchvision==0.21.0
[pip3] triton==3.2.0
[conda] Could not collect
cc @H-Huang @awgu @wanchaol @fegin @fduwjj @wz337 @wconstab @d4l3k