fix: gracefully retire dask workers so srun exits silently#95
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`workers.terminate()` SIGTERM-s the srun process, which then prints "srun: forcing job termination" and "task 0: Killed" to stderr on every clean `lc run` inside a SLURM allocation. Ask the scheduler to retire workers first (close_workers=True): each `dask worker` process exits on its own, srun's task returns code 0, and srun terminates silently. SIGTERM/SIGKILL remain as fallbacks if retire_workers fails or workers don't exit within 20s. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
✅ Eval Results
Graders✅ spec_valid (1.00) Full output |
When retire_workers(close_workers=True) tells the worker to exit on shutdown, the parent Nanny sees the child die and logs "Worker process died unexpectedly" before it picks up the graceful-close flag. Drop the Nanny: each srun task is a single run-scoped worker, so auto-restart doesn't help (srun wouldn't relaunch the task anyway). The worker process exits cleanly when retired and srun terminates silently. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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Summary
Test plan
Notes
Independent of #94 (the dask logger env-var fix); both touch `_slurm_backed_cluster` but in different sections, so whichever lands first will need a trivial rebase of the other.
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