[Draft] Hotfix: Add env variables to overcome A3 highgpu failure

[SwarnaBharathiMantena]

The NCCL test failure with WEXITSTATUS 3 was caused by a missing environment variable in the Slurm Prolog/Epilog wrapper scripts.

Root Cause Analysis

1. TCPX Initialization: NCCL tests on A3 HighGPU nodes require the rxdm (Receive Data Path Manager) script to create Unix Domain
   Sockets in /run/tcpx-${SLURM_JOB_ID}. These sockets are then mounted into the Enroot container.
2. Multiplexer Failure: The rxdm script is executed via a multiplexer script (slurm_mux). This multiplexer depends on the
   SLURM_SCRIPT_CONTEXT environment variable to determine which scripts to run (e.g., prolog_slurmd or epilog_slurmd).
3. Missing Context: The wrapper scripts external_prolog.sh and external_epilog.sh were calling slurm_mux without setting
   SLURM_SCRIPT_CONTEXT. Consequently, slurm_mux skipped all scripts, including rxdm.
4. Container Startup Failure: Because rxdm did not run, the /run/tcpx-${SLURM_JOB_ID} directory was never created on the compute
   nodes. When srun attempted to start the container, the mount operation failed because the source directory did not exist,
   leading to exit code 3.

Fixes Applied
Updated the following files in the schedmd-slurm-gcp-v6-controller module:

• community/modules/scheduler/schedmd-slurm-gcp-v6-controller/modules/slurm_files/files/external_prolog.sh: Now exports
  SLURM_SCRIPT_CONTEXT="prolog_slurmd".
• community/modules/scheduler/schedmd-slurm-gcp-v6-controller/modules/slurm_files/files/external_epilog.sh: Now exports
  SLURM_SCRIPT_CONTEXT="epilog_slurmd".

These changes ensure that custom prologs and epilogs (including TCPX setup) are correctly identified and executed by the multiplexer.

[gemini-code-assist]

Summary of Changes

Hello @SwarnaBharathiMantena, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request resolves a critical issue causing NCCL test failures on A3 HighGPU nodes by ensuring that Slurm's external prolog and epilog wrapper scripts correctly set the SLURM_SCRIPT_CONTEXT environment variable. This rectifies a problem where the slurm_mux multiplexer was skipping essential setup scripts, such as rxdm for TCPX initialization, leading to container startup failures due to missing directories. The changes guarantee proper execution of custom Slurm hooks, resolving the underlying cause of the test failures.

Highlights

• Environment Variable Export: The SLURM_SCRIPT_CONTEXT environment variable is now explicitly exported in external_prolog.sh and external_epilog.sh scripts. This ensures that the slurm_mux multiplexer correctly identifies and executes custom prolog and epilog scripts, including the rxdm script required for TCPX initialization.
• NCCL Test Failure Resolution: This change directly addresses the NCCL test failure with WEXITSTATUS 3 on A3 HighGPU nodes, which was caused by the rxdm script not running due to the missing environment variable, leading to container startup failures.

Changelog

• community/modules/scheduler/schedmd-slurm-gcp-v6-controller/modules/slurm_files/files/external_epilog.sh
  • Added export SLURM_SCRIPT_CONTEXT="epilog_slurmd" to ensure the correct context is set for the epilog script.
• community/modules/scheduler/schedmd-slurm-gcp-v6-controller/modules/slurm_files/files/external_prolog.sh
  • Added export SLURM_SCRIPT_CONTEXT="prolog_slurmd" to ensure the correct context is set for the prolog script.

Activity

• No human activity has been recorded on this pull request yet.

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[gemini-code-assist]

Code Review

This pull request addresses a critical issue with NCCL test failures on A4 HighGPU nodes by ensuring the SLURM_SCRIPT_CONTEXT environment variable is set correctly in the prolog and epilog wrapper scripts. The fix is direct and well-explained in the description. My review includes a couple of suggestions to add comments to the code, which will improve long-term maintainability by explaining the purpose of this variable directly in the scripts, in line with the project's style guide. The provided rule regarding variable configurability does not apply to these comments, as they focus on documenting hardcoded values rather than making them configurable.

[SwarnaBharathiMantena]

Did not fix the issue. Debugging futher.