[NopeCharon]

What this PR does / why we need it:

Adds a typeConverter filter to ClusterFilter and Filter, for Fluent Bit's type_converter plugin. Until now the only way to use it was customPlugin.

There is one list for each source type Fluent Bit supports: intKeys, uintKeys, floatKeys and strKeys. Each entry has a fromKey, a toKey and the target type:

spec:
  match: "*"
  filters:
    - typeConverter:
        uintKeys:
          - fromKey: Mem.total
            toKey: Mem.total_str
            type: string
        strKeys:
          - fromKey: code
            toKey: code_int
            type: int

This renders as:

[Filter]
    Name    type_converter
    Match    *
    Uint_Key    Mem.total Mem.total_str string
    Str_Key    code code_int int

In the YAML config format, a key with several conversions becomes a list.

I used structured entries rather than raw "FROM TO TYPE" strings so the CRD can check them. Fluent Bit wants exactly three tokens per entry and won't start without at least one rule ([filter:type_converter] no rules). So the API server rejects:

• keys that are empty or contain whitespace
• types other than int, uint, float and string
• empty lists, and a typeConverter with no conversions (a CEL rule)

The deepcopy code, CRDs, setup.yaml and API docs are regenerated, and the filter is listed in docs/plugins/fluentbit/index.md.

Which issue(s) this PR fixes:

Fixes #2131

Does this PR introduced a user-facing change?

Add the type_converter filter plugin to the Fluent Bit ClusterFilter and Filter.

Additional documentation, usage docs, etc.:

New docs/plugins/fluentbit/filter/type_converter.md

Testing

• TestFilter_TypeConverter_Params checks the rendered parameters, including several entries for one key and an empty filter.
• TestClusterFilterList_Load_TypeConverter checks the classic and YAML output of a ClusterFilter.
• make test, make lint, make verify and make generate manifests docs-update pass locally, with no diff left over.
• I ran both rendered configs (classic and YAML) on fluent/fluent-bit:5.2.0 with a dummy input, and the converted fields showed up with the right types, e.g. "code_int":404,"ratio_float":0.5,"n_str":"42".
• I applied the generated CRD to an envtest API server. A valid ClusterFilter is accepted. An empty typeConverter, an empty list, an unsupported type, an empty key and a key with a space are all rejected with the messages above.

[cvas22]

Checked the classic and YAML output against the Fluent Bit type_converter docs: one Int_Key/Uint_Key/Float_Key/Str_Key line per conversion in classic, and the repeated keys turn into a list in YAML, which is what the YAML loader expects. The CEL rule for at least one list makes sense too. Looks good to me.

[marcofranssen]

Can you rebase to resolve the conflicts?

[NopeCharon]

Rebased onto master and resolved the conflicts (kept both sysinfo and typeConverter).