Fix potential deadlock in health streamer

[GuptaManan100]

Description

While we fixed a couple of deadlocks in #17230, one was left pending. It was found while testing for deadlocks in #17238.

The deadlock is similar to the ones fixed in #17230, it was occurring between MakePrimary and the reload. The fix employed is to let go of the lock once it is not required instead of defering its unlocking.

Related Issue(s)

• Bug Report: Deadlock in messager engine #17229

Checklist

• "Backport to:" labels have been added if this change should be back-ported to release branches
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Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 67.39%. Comparing base (2c6e053) to head (eadb128).
Report is 5 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #17261   +/-   ##
=======================================
  Coverage   67.39%   67.39%           
=======================================
  Files        1570     1573    +3     
  Lines      252970   253060   +90     
=======================================
+ Hits       170484   170559   +75     
- Misses      82486    82501   +15     

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[mdlayher]

If we're able, you could consider swapping this for the fairly new atomic.Bool in Go to eliminate this lock all together!

[arthurschreiber]

If we're able, you could consider swapping this for the fairly new atomic.Bool in Go to eliminate this lock all together!

I don't think that's possible here, because we depend on a consistent view over multiple fields (isServingPrimary, state).

[arthurschreiber]

LGTM

[mdlayher]

If a consistent view over multiple fields is necessary then https://pkg.go.dev/sync/atomic#Pointer with a struct is also an option. No strong feelings, just wanted to offer a suggestion to eliminate the lock.

[shlomi-noach]

Looks good