fix: healthcheck not responding

[LesnyRumcajs]

Summary of changes

Changes introduced in this pull request:

• this should improve the overall performance of the node given shorter critical section for widely used fields,
• introduced small timeouts for local checks so that the healthcheck is snappy - the default for F3 is 60s and for the simple connection probably something OS-specific - too long!

Reference issue to close (if applicable)

Closes #6515

Other information and links

Change checklist

• I have performed a self-review of my own code,
• I have made corresponding changes to the documentation. All new code adheres to the team's documentation standards,
• I have added tests that prove my fix is effective or that my feature works (if possible),
• I have made sure the CHANGELOG is up-to-date. All user-facing changes should be reflected in this document.

Outside contributions

• I have read and agree to the CONTRIBUTING document.
• I have read and agree to the AI Policy document. I understand that failure to comply with the guidelines will lead to rejection of the pull request.

Summary by CodeRabbit

• Bug Fixes

  • Added short timeouts to health checks to improve responsiveness and avoid hangs during service delays.

• Refactor

  • Made synchronization status updates safer and more efficient by switching to a non-mutating update pattern that reduces contention.
  • Improved peer-failure handling with early short-circuiting for known bad peers to reduce overhead and speed recovery.

[coderabbitai]

Walkthrough

Refactors sync-status update to an immutable read-clone-compute-write pattern, adds a 2s timeout to health probe operations to avoid stalled checks, and short-circuits peer-failure logging via a pre-check against bad_peers.

Changes

Cohort / File(s)	Summary
Chain Sync Refactor src/chain_sync/sync_status.rs, src/chain_sync/chain_follower.rs	SyncStatusReport::update changed from &mut self to &self -> Self and now returns a new report. chain_follower reads/clones the status, computes a new report, then writes it back (reduces write-lock hold and removes in-place mutation).
Health Check Timeout Protection src/health/endpoints.rs, Cargo.toml	Adds MAX_REQ_DURATION_SECS = 2 and wraps check_rpc_server_running and check_f3_running calls with tokio::time::timeout to prevent /livez stalls. Minor Cargo change included.
Peer Manager Control Flow src/libp2p/peer_manager.rs	log_failure now does a read-lock pre-check against bad_peers and returns early for bad peers; per-peer metrics and write-lock updates only run for non-bad peers (changes synchronization/check order).

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Possibly related PRs

• fix(gc): schedule automatic GC only when the node is in sync #6165: Overlaps changes to sync-status update semantics and chain_follower locking patterns.
• fix: add F3 pending activation status to healthcheck API #6415: Also modifies src/health/endpoints.rs and the F3 health check behavior (related timeout/healthcheck fixes).

Suggested reviewers

• akaladarshi
• hanabi1224
• elmattic

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 57.14% 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
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title 'fix: healthcheck not responding' clearly relates to the primary objective of preventing healthcheck endpoints from stalling, matching the linked issue.
Linked Issues check	✅ Passed	The PR addresses key requirements from issue #6515: adds small timeouts to RPC and F3 health checks in endpoints.rs, reduces lock duration in chain_sync modules to prevent stalling, and prevents blocking during healthcheck operations.
Out of Scope Changes check	✅ Passed	All changes align with the stated objectives: timeout additions to health checks, lock duration optimizations in sync modules, and peer manager improvements are all within scope of preventing healthcheck stalling.

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✨ Finishing touches

• 📝 Generate docstrings

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch fix-healthchecks-slow

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[coderabbitai]

Actionable comments posted: 3

🤖 Fix all issues with AI agents

In `@src/chain_sync/sync_status.rs`:
- Around line 162-168: The trace log is printing the old field
self.epochs_behind instead of the freshly computed local epochs_behind; update
the log::trace! call in the SyncStatus reporting code to use the local variable
epochs_behind (computed from
network_head_epoch.saturating_sub(current_head_epoch)) so the logged "epochs
behind" reflects the newly computed value rather than the stale
self.epochs_behind.

In `@src/health/endpoints.rs`:
- Around line 174-180: The current timeout check only tests that the timeout did
not elapse, not that F3 actually returned Ok(true); change the condition that
currently uses tokio::time::timeout(...).await.is_ok() to explicitly inspect the
nested Result from tokio::time::timeout and F3IsRunning::is_f3_running() (e.g.,
match or if let to require Ok(Ok(true))) so the branch only runs when the
timeout completed and the inner call returned Ok(true); update the code
surrounding F3IsRunning::is_f3_running() and MAX_REQ_DURATION_SECS accordingly.
- Around line 144-150: The current check uses
tokio::time::timeout(...).await.is_ok(), which only verifies the timeout didn't
elapse and not whether tokio::net::TcpStream::connect actually succeeded; change
the logic around tokio::time::timeout, MAX_REQ_DURATION_SECS, and
state.config.client.rpc_address to await the timeout result and explicitly
handle its nested Result: treat Ok(Ok(_stream)) as a successful connection, and
treat Ok(Err(_err)) or Err(_elapsed) as failures (log/return the RPC-down path
accordingly), so the endpoint only reports "rpc server running" when the connect
call truly succeeded.

[codecov]

Codecov Report

❌ Patch coverage is 13.95349% with 37 lines in your changes missing coverage. Please review.
✅ Project coverage is 63.31%. Comparing base (46ac35d) to head (a6bddf0).
⚠️ Report is 4 commits behind head on main.

Files with missing lines	Patch %	Lines
src/chain_sync/sync_status.rs	0.00%	20 Missing ⚠️
src/libp2p/peer_manager.rs	0.00%	7 Missing ⚠️
src/health/endpoints.rs	50.00%	6 Missing ⚠️
src/chain_sync/chain_follower.rs	0.00%	4 Missing ⚠️

Additional details and impacted files

Files with missing lines	Coverage Δ
src/chain_sync/chain_follower.rs	39.54% <0.00%> (-0.13%)	⬇️
src/health/endpoints.rs	89.47% <50.00%> (-2.89%)	⬇️
src/libp2p/peer_manager.rs	22.92% <0.00%> (-0.12%)	⬇️
src/chain_sync/sync_status.rs	12.00% <0.00%> (-1.34%)	⬇️

... and 6 files with indirect coverage changes

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