[fluent-bit] Adding support of StatefulSet

[anosulchik]

It might be useful to run fluent-bit in StatefulSet mode when for example it's configured with storage persistence.

Here's an example setup with persisted storage where StatefulSet is needed for middleware fluent-bit:

client fluent-bit [forward_out] --> [forward_in] middleware fluent-bit [...] --> [...]

In order to mount volume in StatefulSet, add this into your helm values:

values:
   extraVolumeMounts:
   - name: fluent-bit-middleware-buffer
     mountPath: /var/lib/fluent-bit

   config:
     service: |
        [SERVICE]
            storage.path /var/lib/fluent-bit
            ...

P.S. Suggested change is based on implementation of StatefulSet for fluentd helm chart.

[anosulchik]

@edsiper @stevehipwell @naseemkullah Guys, can you please review this PR and let me know if there's something wrong with it? Thanks.

[stevehipwell]

@anosulchik I'm in the process of adding specific collector (DaemonSet) and aggregator (StatefulSet) charts for both Fluent Bit and Fluentd; these will be tightly constrained and focused on doing one thing as well as possible.

For this reason I'm not keen on adding extra complexity to this chart as once the new charts are available I'll be focusing my effort on them.

[ksauzz]

Hi, I'm also curious about statefulset support to manage fluent-bit as aggregator. Although we have managed fluent-bit aggregator as statefulset with this patch for about 1 year, it would be nice for us to consider to merge this PR if releasing the new charts takes more efforts.

Thank you for your consideration.