etcdmain: centralize exit handling

[majiayu000]

What\n- funnel startEtcdOrProxyV2 exit paths through a single osutil.Exit call\n- convert config parsing help/version/flag exits into exit errors\n- add a small exit code helper for etcdmain\n\n## Why\nFollow-up to #21032 (step 2 after #21062) to unify exit calls.\n\n## Testing\n- not run (not requested)

[k8s-ci-robot]

Hi @majiayu000. Thanks for your PR.

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[serathius]

This doesn't follow the proposal at #21032 (comment), please align.

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: majiayu000, serathius

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[serathius]

Please sign the DCO

[majiayu000]

Sorry for the dco, caused by a new computer.

[serathius]

/ok-to-test

[serathius]

/cc @fuweid @ahrtr

[k8s-ci-robot]

@majiayu000: The following test failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
pull-etcd-verify	2f8b52b	link	true	/test pull-etcd-verify

Full PR test history. Your PR dashboard. Please help us cut down on flakes by linking to an open issue when you hit one in your PR.

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[codecov]

Codecov Report

❌ Patch coverage is 0% with 33 lines in your changes missing coverage. Please review.
✅ Project coverage is 68.48%. Comparing base (a438759) to head (2f8b52b).
⚠️ Report is 4 commits behind head on main.

Files with missing lines	Patch %	Lines
server/etcdmain/etcd.go	0.00%	29 Missing ⚠️
server/etcdmain/config.go	0.00%	4 Missing ⚠️

Additional details and impacted files

Files with missing lines	Coverage Δ
server/etcdmain/config.go	72.51% <0.00%> (ø)
server/etcdmain/etcd.go	0.00% <0.00%> (ø)

... and 17 files with indirect coverage changes

@@            Coverage Diff             @@
##             main   #21081      +/-   ##
==========================================
+ Coverage   68.44%   68.48%   +0.03%     
==========================================
  Files         429      429              
  Lines       35281    35303      +22     
==========================================
+ Hits        24149    24178      +29     
+ Misses       9732     9729       -3     
+ Partials     1400     1396       -4     

---

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[serathius]

Please fix:

../server/etcdmain/config.go:133:49: non-wrapping format verb for fmt.Errorf. Use `%w` to format errors (errorlint)
		return fmt.Errorf("%w: %v", ErrArgumentError, perr)
		                                              ^
../server/etcdmain/etcd.go:82:75: non-wrapping format verb for fmt.Errorf. Use `%w` to format errors (errorlint)
			return fmt.Errorf("%w: error creating zap logger %v", ErrGeneralError, zapError)
			                                                                       ^
../server/etcdmain/etcd.go:94:72: non-wrapping format verb for fmt.Errorf. Use `%w` to format errors (errorlint)
		return fmt.Errorf("%w: failed to verify flags %v", ErrArgumentError, err)
		                                                                     ^
../server/etcdmain/etcd.go:166:66: non-wrapping format verb for fmt.Errorf. Use `%w` to format errors (errorlint)
			return fmt.Errorf("%w: discovery failed %v", ErrGeneralError, err)
			                                                              ^
../server/etcdmain/etcd.go:180:65: non-wrapping format verb for fmt.Errorf. Use `%w` to format errors (errorlint)
			return fmt.Errorf("%w: failed to start %v", ErrGeneralError, err)
			                                                             ^
../server/etcdmain/etcd.go:183:65: non-wrapping format verb for fmt.Errorf. Use `%w` to format errors (errorlint)
		return fmt.Errorf("%w: discovery failed %v", ErrGeneralError, err)
		                                                              ^
../server/etcdmain/etcd.go:199:64: non-wrapping format verb for fmt.Errorf. Use `%w` to format errors (errorlint)
		return fmt.Errorf("%w: listener failed %v", ErrGeneralError, lerr)
		```

[fuweid]

what about returning nil here?
without ErrExitOK, it's easy to handle error

[majiayu000]

Thanks for the comment!

The reason for using ErrExitOK instead of nil is to control the execution flow.

In startEtcdOrProxyV2Error, we call cfg.parse(args). If cfg.parse returns nil (as suggested for the --help case), the function would assume everything is fine and continue to execute the subsequent logic (initializing the logger and eventually calling startEtcd to boot up the server).

For --help and --version, we want to terminate the flow immediately and exit with 0. Since we wanted to avoid calling os.Exit deeply inside config.go, returning a specific sentinel error ErrExitOK allows us to bubble up this "exit request" to the main entry point and handle it gracefully there.