improve health checker for adapting coordinator

[rambohe-ch]

What type of PR is this?

Uncomment only one /kind <> line, hit enter to put that in a new line, and remove leading whitespace from that line:
/kind bug
/kind documentation
/kind enhancement
/kind good-first-issue
/kind feature
/kind question
/kind design
/sig ai
/sig iot
/sig network
/sig storage

/kind feature

What this PR does / why we need it:

In order to check the healthy status of pool-coordinator component in the NodePool, the HealthChecker module is need to improved to adapt two kinds backends. so several Interfaces have been added:

• HealthChecker: health checker for pool-coordinator component
• MultipleBackendsHealthChecker: health checker for kube-apiservers on cloud
• BackendProber: used for sending heartbeat to backend.

btw: the detail info about pool coordinator, please dive into the following proposals:

• https://github.com/openyurtio/openyurt/blob/master/docs/proposals/20220307-nodepool-governance-capability.md
• https://github.com/openyurtio/openyurt/blob/master/docs/proposals/20220414-multiplexing-cloud-edge-traffic.md

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?

other Note

[openyurt-bot]

@rambohe-ch: GitHub didn't allow me to assign the following users: your_reviewer.

Note that only openyurtio members, repo collaborators and people who have commented on this issue/PR can be assigned. Additionally, issues/PRs can only have 10 assignees at the same time.
For more information please see the contributor guide

In response to this:

What type of PR is this?

Uncomment only one /kind <> line, hit enter to put that in a new line, and remove leading whitespace from that line:
/kind bug
/kind documentation
/kind enhancement
/kind good-first-issue
/kind feature
/kind question
/kind design
/sig ai
/sig iot
/sig network
/sig storage

/kind feature

What this PR does / why we need it:

In order to check the healthy status of pool-coordinator component in the NodePool, the HealthChecker module is need to improved to adapt two kinds backends. so several Interfaces have been added:

• HealthChecker: health checker for pool-coordinator component
• MultipleBackendsHealthChecker: health checker for kube-apiservers on cloud
• BackendProber: used for sending heartbeat to backend.

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?

other Note

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[rambohe-ch]

@Congrool @donychen1134 @gnunu @luc99hen PTAL

[codecov]

Codecov Report

Merging #1032 (4db7624) into master (2a67506) will increase coverage by 0.81%.
The diff coverage is 86.82%.

@@            Coverage Diff             @@
##           master    #1032      +/-   ##
==========================================
+ Coverage   48.15%   48.96%   +0.81%     
==========================================
  Files          95       96       +1     
  Lines       13010    13053      +43     
==========================================
+ Hits         6265     6392     +127     
+ Misses       6209     6130      -79     
+ Partials      536      531       -5     

Flag	Coverage Δ
unittests	48.96% <86.82%> (+0.81%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
pkg/yurthub/healthchecker/fake_checker.go	0.00% <0.00%> (ø)
pkg/yurthub/healthchecker/node_lease.go	91.00% <ø> (+19.00%)	⬆️
pkg/yurthub/proxy/remote/loadbalancer.go	46.15% <40.00%> (+6.15%)	⬆️
pkg/yurthub/healthchecker/health_checker.go	85.95% <87.50%> (+33.56%)	⬆️
pkg/yurthub/healthchecker/prober.go	96.34% <96.34%> (ø)
pkg/yurthub/kubernetes/rest/config.go	61.53% <100.00%> (ø)
pkg/yurthub/proxy/remote/remote.go	1.35% <100.00%> (+<0.01%)	⬆️
pkg/util/iptables/iptables.go	87.67% <0.00%> (+0.54%)	⬆️

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.

[gnunu]

/LGTM

[openyurt-bot]

@gnunu: changing LGTM is restricted to collaborators

In response to this:

/LGTM

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[openyurt-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: gnunu, rambohe-ch

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• OWNERS [rambohe-ch]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[Congrool]

/lgtm