feat(config): emit log changed global fields and metric vector_config_reload_rejected when reload is rejected

[suikammd]

Summary

This PR add vector_config_reload_rejected{reason="global_options"} metric and internal event to observe rejected config reloads caused by GlobalOptions changes.

[suikammd]

#1815
Also, would you be open to adding a force_reload flag that allows hot reloads even if GlobalOptions have changed?

I understand this is currently blocked for safety, but in some cases we’d prefer to reload anyway. If you're open to it, I’d be happy to submit a PR. Of course, it would be opt-in and disabled by default.

Let me know — thanks!

[pront]

Thanks @suikammd, this is a nice UX improvement.

[pront]

There are quite a few checks failing. Let me know if you need help addressing them.

[pront]

Hmm I think it would be best to keep the original PR and introduce the metric in a follow up.

Also, while looking at the ReloadRejectReason::GlobalOptionsChanged gauge, I realized that we can probably do something more generic here. Something like emitting reload signals for various reasons e.g. event="config reloaded", event="failed to reload", reason="global options changed".

[pront]

Hi @suikammd, there are a few failing checks.

Hmm I think it would be best to keep the original PR and introduce the metric in a follow up.

Let's go with this approach so we can end up with a better result.

[suikammd]

Hi @pront , thanks for the suggestion!
I’ve split the work into two PRs as you suggested. Once the new PR(#23662 ) is merged, I’ll rebase this one accordingly.

[thomasqueirozb]

#23662 merged!

We will take a look at this PR again once merge conflicts are fixed :)