Reduce ERROR log spam for expected NoSuchKey responses

[VershaAgrawal]

Describe the Problem

Expected missing-object lookups (e.g. Thanos marker GETs) were treated like failures. Every NoSuchKey / NO_SUCH_OBJECT was logged at ERROR with a full stack.

Explain the Changes

1. Demote expected missing-object outcomes to quiet dbg.log1 (no stack): NoSuchKey on GET/HEAD in s3_rest.js, and NO_SUCH_OBJECT in rpc.js (_request and _on_request). S3/RPC responses are unchanged (still 404 NoSuchKey); all other errors (auth, NoSuchBucket, internal failures, etc.) continue to log at ERROR with stack.

Issues: Fixed #xxx / Gap #xxx

1. https://redhat.atlassian.net/browse/DFBUGS-9093

Testing Instructions:

• Doc added/updated
• Tests added

Summary by CodeRabbit

• Bug Fixes
  • Reduced unnecessary error logging for expected missing-object responses from storage and RPC requests.
  • Missing-object errors are now recorded as informational or debug messages without detailed request data or stack traces.
  • Other errors continue to receive detailed logging for troubleshooting.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

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Run ID: c65e4d99-a3ae-49ed-b121-363e2a6494ee

📥 Commits

Reviewing files that changed from the base of the PR and between fcb149f and 1c608df.

📒 Files selected for processing (2)

• src/endpoint/s3/s3_rest.js
• src/rpc/rpc.js

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📝 Walkthrough

Walkthrough

The change reduces log detail for expected missing-object errors. S3 GET and HEAD NoSuchKey errors use informational logs. RPC NO_SUCH_OBJECT errors use concise debug logs. Other errors keep detailed logging.

Changes

Expected missing-object logging

Layer / File(s)	Summary
S3 missing-key logging src/endpoint/s3/s3_rest.js	S3 XML and HTML handlers log NoSuchKey errors for GET and HEAD requests at informational level. Other errors retain detailed logging.
RPC missing-object logging src/rpc/rpc.js	RPC request and server handlers log NO_SUCH_OBJECT errors without request parameters or stack traces. Other errors retain detailed logging.

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

Merge Risk: ⚪ Minimal · up to 1c608

This localized change reduces noisy error logging for expected missing-object responses while preserving response behavior and error logging for other failures; no actionable merge-blocking risk remains.

Suggested reviewers: naveenpaul1, liranmauda, aayushchouhan09

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly describes the main change: reducing error-log noise for expected NoSuchKey responses.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[naveenpaul1]

Do we need to include NO_SUCH_OBJECT also?

[naveenpaul1]

can we add JSON.stringify(req.headers) too?