Fluent Bit supports both a classic configuration file format and a YAML format. The support for YAML reflects industry direction. But if you’ve come from Fluentd to Fluent Bit or have been using Fluent Bit from the early days, you’re likely to be using the classic format. The differences can be seen here:

[SERVICE]
    flush 5
    log_level debug
[INPUT]
   name dummy
   dummy {"key" : "value"}
   tag blah
[OUTPUT]
   name stdout
   match *
#
# Classic Format
#

service:
    flush: 1
    log_level: info
pipeline:
    inputs:
        - name: dummy
          dummy: '{"key" : "value"}'
          tag: blah
    outputs:
        - name: stdout
          match: "*"
#
# YAML Format
#

Why migrate to YAML?

Beyond having a consistent file format, the driver is that some new features are not supported by the classic format. Currently, this is predominantly for Processors; it is fair to assume that any other new major features will likely follow suit.

Migrating from classic to YAML

The process for migrating from classic to YAML has two dimensions:

• Change of formatting
  • YAML indentation and plugins as array elements
  • addressing any quirks such as wildcard (*) being quoted, etc
• Addressing constraints such as:
  • Using include is more restrictive
  • Ordering of inputs and outputs is more restrictive – therefore match attributes need to be refined.

None of this is too difficult, but doing it by hand can be laborious and easy to make mistakes. So, we’ve just built a utility that can help with the process. At the moment, this solution is in an MVP state. But we hope to have beefed it up over the coming few weeks. What we plan to do and how to use the util are all covered in the GitHub readme.

The repository link (fluent-bit-classic-to-yaml-converter)

Update 4th July 24

A quick update to say that we now have a container configuration in the repository to make the tool very easy to use. All the details will be included in the readme, along with some additional features.

Update 7th July

We’ve progressed past the MVP state now. The detected include statements get incorporated into a proper include block but commented out.

We’ve added an option to convert the attributes to use Kubernetes idiomatic form, i.e., aValue rather than a_value.

The command line has a help option that outputs details such as the control flags.

Update 12th July

In the last couple of days, we pushed a little too quickly to GitHub and discovered we’d broken some cases. We’ve been testing the development a lot more rigorously now, and it helps that we have the regression container image working nicely. The Javadoc is also generating properly.

We have identified some edge cases that need to be sorted, but most scenarios have been correctly handled. Hopefully, we’ll have those edge scenarios fixed tomorrow, so we’ll tag a release version then.