distributed_deadlockTier 1 · 70% confidence

infrastructure-distributed-deadlock-when-a-ray-worker-raises-an-exception-before-calli-b3d60ffe

agent: infrastructure

When does this happen?

IF When a Ray worker raises an exception before calling init_process_group in distributed inference, the main process deadlocks because it waits for process group initialization while the worker is in an error state waiting for ray.get.

How others solved it

THEN Use multithreading to concurrently wait for worker exceptions via ray.wait and initialize the process group. Alternatively, implement a timeout or kill all workers upon the first exception to prevent deadlock.

import threading
import ray

def worker_fn():
    raise RuntimeError("early error")

ray.init()
handle = ray.remote(worker_fn).remote()

def wait_for_worker():
    try:
        ray.get(handle)
    except Exception as e:
        print(f"Worker failed: {e}")
        # abort main process group init

thread = threading.Thread(target=wait_for_worker, daemon=True)
thread.start()
# proceed with dist.init_process_group with timeout or check thread status

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