packaging: switch to YAML config files by default

[patrick-stephens]

Resolves #9714 by switching to using YAML configuration by default for all packages and containers.

For containers we should prepare a PR for the helm chart as well but it will not break the helm chart as that explicitly uses a .conf file for now.

We should ensure this is properly notified during the release notes and beforehand for folks to do any required updates to their rollouts.

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Testing
Before we can approve your change; please submit the following in a comment:

• Example configuration file for the change
• Debug log output from testing the change

• Attached Valgrind output that shows no leaks or memory corruption was found

If this is a change to packaging of containers or native binaries then please confirm it works for all targets.

• Run local packaging test showing all targets (including any new ones) build.
• Set ok-package-test label to test for all targets (requires maintainer to do).

Documentation

• Documentation required for this feature
  installation: switch to YAML config files by default fluent-bit-docs#1551

Backporting

• Backport to latest stable release.

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[patrick-stephens]

cc @stevehipwell on the helm side - the current chart uses a legacy config by default so should not be impacted by this change but maybe we should change the defaults there too?

• https://github.com/fluent/helm-charts/blob/79a39754f24bfd8f9396ddf207b41b48597999cb/charts/fluent-bit/values.yaml#L376
• https://github.com/fluent/helm-charts/blob/79a39754f24bfd8f9396ddf207b41b48597999cb/charts/fluent-bit/values.yaml#L494

[stevehipwell]

@patrick-stephens is the YAML support now idiomatic? I saw flush: 1 when I just gave this a quick scan.

[patrick-stephens]

@patrick-stephens is the YAML support now idiomatic? I saw flush: 1 when I just gave this a quick scan.

There's no change to syntax here, this is primarily around the default config file we're using.

[stevehipwell]

So in the context of Kubernetes I think the current "YAML" format is problematic given the fact that it's not idiomatic YAML but is called YAML and looks like YAML. That said am I correct in understanding that some capabilities are only available via the YAML config?

[patrick-stephens]

So in the context of Kubernetes I think the current "YAML" format is problematic given the fact that it's not idiomatic YAML but is called YAML and looks like YAML. That said am I correct in understanding that some capabilities are only available via the YAML config?

Sorry @stevehipwell missed this but yes, processors are the main one that is only available via YAML config: https://docs.fluentbit.io/manual/pipeline/processors
(All existing filters can be processors too). There's some other stuff like multi-line content that is only possible, e.g. for LUA filters.

I think the main thing on the chart side is making it easy to switch to format.

At the moment I think this is a minimal YAML config for the chart but it leaves all the default config in place:

args:
  - --workdir=/fluent-bit/etc
  - --config=/fluent-bit/etc/conf/fluent-bit.yaml

config:
 extraFiles:
  fluent-bit.yaml: |
    pipeline:
      inputs:
        - name: tail
          tag: kube.*
          path: /var/log/containers/*.log
          multiline.parser: docker, cri
      outputs:
        - name: stdout
          match: '*'

The current config forces legacy config usage as it uses fluent-bit.conf as the name and the file suffix needs to be .yml or .yaml to handle YAML format: https://github.com/fluent/helm-charts/blob/9e36dfa209c73951370f36549e63163419a8bcf7/charts/fluent-bit/templates/configmap.yaml#L12

The chart is protected against the default format changing as the args value specifies the config file directly. We need to switch this depending on if it is .conf or .yaml.