feat(fluent-bit): Added hot-reload support

[stevehipwell]

No description provided.

[stevehipwell]

This PR is waiting for some external testing and I'll mark it as ready once this has happened.

[stevehipwell]

@edsiper @naseemkullah do you want to take a look at the changes here?

The structural changes are required to support hot-reload as user-overridable files should be in a leaf directory to enable direct Kubernetes ConfigMap or Secret mounting. I'm not sure what the side effects of these changes are but when all paths in the config are absolute I've tested that everything works as expected.

[edsiper]

I think @patrick-stephens would be times better than me to review these changes

[stevehipwell]

@edsiper there are some fundamental questions about how Fluent Bit config and workdir works that I asked @patrick-stephens and he passed on to @leonardo-albertovich (I think I got the GH user correct).

[patrick-stephens]

Looks good to me, some good improvements here as well as the hot reload support.

I would add something to the docs to explain how hot reload is being done via a watcher sidecar. I think we should look at the requirements on port/webserver usage vs just signals too to confirm.

[stevehipwell]

@patrick-stephens this change came from the two Fluent Bit prototype charts I've been working on (see below) and has been extensively tested (as part of the aggregator chart).

• Fluent Bit Aggregator
• Fluent Bit Collector

[patrick-stephens]

@stevehipwell I'm happy with this change to merge whenever you are.

[kyontan]

Hi @stevehipwell

I found that the .Values.volumeMounts got ignored after the release of this.
Since I had overridden config volume with the value, now we have no way to override it.
How can we fix the issue?

6b04c1c#diff-d501e88794e6225fbd785cd688bd23d39ffa17e1cafa6f9a704a5b95a73a10d7L88-L89

[stevehipwell]

@kyontan volumeMounts was removed as we now mount the ConfigMap directly. You can use extraVolumes & extraVolumeMounts to mount additional volumes.