Add comment and test for bio RDB disk transfer receive timeout

[enjoy-binbin]

The disk-saving bio thread bounds its blocking RDB read with
repl_syncio_timeout, and the abort flag is only checked between
reads, so a silent primary can stall the main thread in
cancelReplicationHandshake() for up to that timeout.

No behavior change: just document why repl_syncio_timeout is
used here instead of repl-timeout, and add a test covering the
abort path.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Pro Plus

Run ID: 866347f1-5c92-4de7-9c22-bde570cd0e10

📥 Commits

Reviewing files that changed from the base of the PR and between 90b5fd8 and fc6aaa6.

📒 Files selected for processing (1)

• tests/integration/replication.tcl

---

📝 Walkthrough

Walkthrough

Replication handshake cancellation now documents that a Bio thread blocked in an RDB socket read can delay the main thread up to repl_syncio_timeout. An integration test exercises this behavior during diskless replication.

Changes

Replication handshake cancellation

Layer / File(s)	Summary
Document and test cancellation timeout src/replication.c, tests/integration/replication.tcl	Comments describe timeout behavior in the RDB receive and handshake-cancellation paths. A diskless replication test verifies cancellation while streamed RDB reading is blocked and restores the configured delay afterward.

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

Suggested reviewers: murphyjacob4

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly matches the main change: documenting the RDB receive timeout and adding a test.
Description check	✅ Passed	The description directly explains the timeout rationale and the added abort-path test.
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.

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands.}

[valkey-review-bot]

One concern with the new value: in the bio thread this socket timeout also doubles as the interval at which server.replica_bio_abort_save is observed, and cancelReplicationHandshake() busy-waits on the main thread for that. Details inline.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 76.79%. Comparing base (4733aed) to head (fc6aaa6).
⚠️ Report is 1 commits behind head on unstable.

Additional details and impacted files

@@             Coverage Diff              @@
##           unstable    #4277      +/-   ##
============================================
- Coverage     76.84%   76.79%   -0.05%     
============================================
  Files           162      162              
  Lines         81479    81479              
============================================
- Hits          62610    62571      -39     
- Misses        18869    18908      +39     

Files with missing lines	Coverage Δ
src/replication.c	85.78% <ø> (-0.37%)	⬇️

... and 19 files with indirect coverage changes

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@tests/integration/replication.tcl`:
- Around line 1708-1712: Update the cancellation test around the $replica
replicaof no one call to measure its elapsed duration and assert it stays below
a tolerant upper bound that is shorter than the normal repl-timeout, while
retaining the existing slow-command log assertion.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Pro Plus

Run ID: a250b14c-d16e-4591-b905-9bf95bb15dec

📥 Commits

Reviewing files that changed from the base of the PR and between 70712a9 and 90b5fd8.

📒 Files selected for processing (2)

• src/replication.c
• tests/integration/replication.tcl