fix(machine-controller): report DPU restart outcome accurately

[behroozrafii]

DPU restart handling logged success and queued the reboot-request timestamp before the Redfish restart completed. When the restart failed, logs could falsely imply success, and the lower-level failure log did not identify the affected DPU.

This change:

• Logs the restart attempt before calling Redfish.
• Logs failures with both dpu_machine_id and the returned error.
• Records the reboot-request timestamp and logs success only after the restart succeeds.
• Removes the redundant lower-level failure log while preserving the original error.

This gives operators an accurate restart outcome and identifies the failed DPU without changing any API or configuration.

Related issues

Fixes #3713

Type of Change

• Add - New feature or capability
• Change - Changes in existing functionality
• Fix - Bug fixes
• Remove - Removed features or deprecated functionality
• Internal - Internal changes (refactoring, tests, docs, etc.)

Breaking Changes

• This PR contains breaking changes

Testing

• Unit tests added/updated
• Integration tests added/updated
• Manual testing performed
• No testing required (docs, internal refactor, etc.)
• Existing unit tests run:
  • cargo test -p carbide-machine-controller --lib
  • 56 passed, 0 failed, 0 ignored, 0 measured, 0 filtered out
• Formatting verified:
  • cargo fmt --all -- --check

Additional Notes

No API, configuration, or database-schema changes.

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ℹ️ Recent review info

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📥 Commits

Reviewing files that changed from the base of the PR and between 862b66a and 4fa5d42.

📒 Files selected for processing (1)

• crates/machine-controller/src/handler.rs

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Summary by CodeRabbit

• Bug Fixes
  • DPU restart requests now update reboot status only after the restart succeeds.
  • Failed restart attempts are reported immediately without recording an incorrect reboot-request timestamp.
  • Improved error handling for restart failures.

Walkthrough

The DPU restart handler now performs the Redfish restart before recording reboot-request state or logging success. Restart errors propagate directly, preventing database updates and success logs when the operation fails.

Changes

DPU restart sequencing

Layer / File(s)	Summary
Restart execution and success-gated persistence crates/machine-controller/src/handler.rs	restart_dpu directly propagates Redfish restart errors, while handler_restart_dpu records UpdateRebootRequestedTime and logs success only after a successful restart.

Estimated code review effort: 2 (Simple) | ~10 minutes

Possibly related PRs

• NVIDIA/infra-controller#3845: Modifies DPU reboot sequencing and the timing of reboot intent persistence relative to power operations.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title concisely describes the main change: making DPU restart outcome reporting accurate.
Description check	✅ Passed	The description matches the code changes and clearly explains the restart logging and timestamp behavior.
Linked Issues check	✅ Passed	The implementation matches #3713 by logging attempts before restart, deferring success and DB updates until after success, and preserving failure context.
Out of Scope Changes check	✅ Passed	The changes stay within the restart-handling scope and do not introduce unrelated behavior.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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🧪 Generate unit tests (beta)

• Create PR with unit tests

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