auth: refactor health checks monitoring done from LUA records

[chbruyand]

Short description

This PR puts TCP/IP and URL health checks in a single thread (instead of 1 thread per check).

This also removes checks that have been unused for a given period of time (currently 1 hour). This will prevent checks from modified or deleted records to keep being performed by the authoritative server (fix #7988).

Checklist

I have:

• read the CONTRIBUTING.md document
• compiled this code
• tested this code
• included documentation (including possible behaviour changes)
• documented the code
• added or modified regression test(s)
• added or modified unit test(s)

[chbruyand]

Thanks for your review. I added an extra check on insertion when we have the lock and changed how we store items to be deleted.

[pfak]

This also removes checks that have been unused for a given period of time (currently 1 hour).

Not a fan of this behaviour. But, that being said. I'm not a fan of the current behaviour of not running a check until someones tries to look up the record. Is it possible to make this configurable? I would prefer ALL checks to be run if the record exists, and/or the existing behaviour.

[Someguy123]

The configurable health check would be great - it would help resolve the issue I've just reported: #8261

[sbakhos]

If possible I would like to configure the timeout for the health check too. We're looking at implementing this and noticed in our lab a lot of flapping on some of the longer checks (about 500ms).

[chbruyand]

One or two serious reviews would be more than welcome. Also I don't understand why this broke the dnsdist circleci tests :/

[Habbie]

Also I don't understand why this broke the dnsdist circleci tests :/

Can you see if a rebase fixes that? We had/have an issue with CircleCI running commit X tests against commit Y builds, and we merged an improvement for that on master yesterday.

[chbruyand]

Also I don't understand why this broke the dnsdist circleci tests :/

Can you see if a rebase fixes that? We had/have an issue with CircleCI running commit X tests against commit Y builds, and we merged an improvement for that on master yesterday.

Looks like it works (c) now...

[chbruyand]

Thanks for your review. Invalid options (like source) will now trigger an error before being inserted in the check list.

[Habbie]

rebased