transaction: add contextual logging with start_ts (#267)

[eduralph]

Enrich the transaction lifecycle, plan/retry, and region-cache logging with each transaction's start_ts and region/store context; add commit/rollback outcome logs, log dropping an active transaction under all check levels, and a terminal warn when region-error retries are exhausted. Truncate keys in the one full-key error log. Fix message typos/duplicates and remove dead logger-threading comments. Add a dependency-free capture-logger test and a RUST_LOG note to the README.

Refs #267

Signed-off-by: Eduard Ralph eduard@ralphovi.net

Summary by CodeRabbit

• Documentation
  • Added a new Logging section covering how logging is handled, how to choose a backend, RUST_LOG, and how log levels correspond to transaction lifecycle and operational/error events.
• Bug Fixes
  • Fixed misleading debug output for reverse key scans.
• Improvements
  • Expanded transaction lifecycle/2PC logging with start timestamps and more timing/lock context; refined region error, retry, and cache invalidation logs.
  • Improved logged key prefixes by hex-encoding and truncating for readability.
• Tests
  • Added log-capture assertions to verify lifecycle logs include the transaction start timestamp.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 1807e24c-7fea-498d-844d-fc2ebbc549fe

📥 Commits

Reviewing files that changed from the base of the PR and between feff589 and 56fb14c.

📒 Files selected for processing (1)

• src/transaction/lock.rs

🚧 Files skipped from review as they are similar to previous changes (1)

• src/transaction/lock.rs

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📝 Walkthrough

Walkthrough

This PR expands logging across client operations, region retries, cache updates, and transaction/2PC lifecycles. It adds contextual timestamps and durations, hexadecimal key formatting, log-capture tests, and README guidance for configuring log output.

Changes

Logging improvements

Layer / File(s)	Summary
Logging documentation and client operations README.md, src/raw/client.rs, src/transaction/client.rs	Documents log configuration, fixes the reverse-scan log label, and enriches transaction client lifecycle and garbage-collection messages.
Cache and region retry logging src/region_cache.rs, src/request/plan.rs	Adds cache update/invalidation logs and enriches region retry diagnostics with identifiers, errors, and exhausted-retry warnings.
Reusable key log formatting src/transaction/lock.rs	Makes format_key_for_log crate-visible, formats key prefixes as hexadecimal with 16-byte truncation, and adds unit tests.
Transaction and 2PC lifecycle logging src/transaction/transaction.rs	Adds start timestamp and operation context to transaction, heartbeat, pessimistic lock, Drop, and 2PC logs; updates commit completion details and TransactionStatus debugging.
Transaction log capture validation src/transaction/transaction.rs	Adds a capturing logger and an asynchronous test verifying lifecycle logs include start_ts.

Estimated code review effort: 2 (Simple) | ~15 minutes

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly summarizes the main change: adding contextual transaction logging with start_ts.
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.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[pingyu]

Rest LGTM.

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: iosmanthus, pingyu

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• OWNERS [iosmanthus,pingyu]

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2026-07-11 14:02:44.876463514 +0000 UTC m=+463150.912558570: ☑️ agreed by pingyu.
• 2026-07-11 14:07:17.906659581 +0000 UTC m=+463423.942754627: ☑️ agreed by iosmanthus.