health_check: add Cached custom health checker

[hudayou]

Signed-off-by: Jacky Hu jacky.hu@walmart.com

Commit Message: health_check: add Cached custom health checker
Additional Description: Allow use of cached health check result from an external third party health checker
Risk Level: L
Testing: unit test, manual testing
Docs Changes:
Release Notes:
Platform Specific Features:
[Optional Runtime guard:]
[Optional Fixes #Issue]
[Optional Fixes commit #PR or SHA]
[Optional Deprecated:]
[Optional API Considerations:]

[repokitteh-read-only]

CC @envoyproxy/api-shepherds: Your approval is needed for changes made to (api/envoy/|docs/root/api-docs/).
envoyproxy/api-shepherds assignee is @adisuissa
CC @envoyproxy/api-watchers: FYI only for changes made to (api/envoy/|docs/root/api-docs/).
CC @envoyproxy/dependency-shepherds: Your approval is needed for changes made to (bazel/.*repos.*\.bzl)|(bazel/dependency_imports\.bzl)|(api/bazel/.*\.bzl)|(.*/requirements\.txt)|(.*\.patch).
envoyproxy/dependency-shepherds assignee is @RyanTheOptimist

🐱

Caused by: #24742 was opened by hudayou.

see: more, trace.

[hudayou]

Need to fix some format errors
/wait

[hudayou]

Need to figure out:

1. how to fix windows build
2. why compile_time_options ci failed?
3. add more tests for code coverage

/wait

[adisuissa]

Thanks.
Can you provide some more background about this extension in the PR description (also is there a tracking issue)?

[adisuissa]

Can/should the cached server be an upstream cluster?
This should take care of all the connection parameters.

[hudayou]

No, this parameters are for a cache server
The purpose is to avoid query upstream cluster and just use the cache

https://github.com/envoyproxy/envoy/blob/badad5f2aadde7523be4e422146ff10a099055db/source/extensions/health_checkers/cached/hiredis.cc

[hudayou]

Thanks. Can you provide some more background about this extension in the PR description (also is there a tracking issue)?

Yep, we are using a redis cache to avoid excessive/unnecessary health checks to our backend servers.

Below is some description about it.

I'll update the PR description about it. There is no tracking issue, if needed by you I can create one.

https://github.com/envoyproxy/envoy/blob/badad5f2aadde7523be4e422146ff10a099055db/docs/root/configuration/upstream/health_checkers/cached.rst

[hudayou]

Need to fix windows build issue by providing alias to static libs as required
/wait

[mattklein123]

Hi,

Thanks for the contribution. We can't accept a contribution this large without a tracking issue, small design doc, etc. Also, this extension would need a sponsor to go in the main repo vs. contrib. Please read the contributing guide. I'm going to close this for now until we sort that out.

Thanks

[hudayou]

Sorry, I apologize for not providing a issue, I'll provide it today.

[hudayou]

Created issue as required here.

#24757