Plugin Helper: Formatter

The formatter plugin helper manages the lifecycle of the formatter plugin.

Here is an example:

require 'fluent/plugin/output'

module Fluent::Plugin
  class ExampleOutput < Output
    Fluent::Plugin.register_output('example', self)

    # 1. Load formatter helper
    helpers :formatter

    # Omit `shutdown` and other plugin APIs

    def configure(conf)
      super

      # 2. Call `formatter_create` to create object
      @formatter = formatter_create(usage: 'awesome_formatter')
    end

    def format(tag, time, record)
      # 3. Call `format` method to format `record`
      @formatter.format(tag, time, record)
    end
  end
end

For more details, see the following articles:

• Formatter Plugin Overview
• Writing Formatter Plugins
• Format Section

Methods

formatter_create(usage: "", type: nil, conf: nil, default_type: nil)

• usage: unique name required for multiple formatters

• type: formatter type

• conf: formatter plugin configuration

• default_type: default formatter type

Examples:

def configure(conf)
  super
  # Create formatter plugin instance using <format> section in `fluent.conf` during configure phase
  @formatter = formatter_create
end

def format(tag, time, record)
  @formatter.format(tag, time, record)
end

JSON formatter example:

# Create JSON formatter
def configure(conf)
  super
  @json_formatter = formatter_create(usage: 'formatter_in_example_json', type: 'json')
end

def format(tag, time, record)
  @json_formatter.format(tag, time, record)
end

MsgPack formatter example:

# Create MsgPack formatter
def configure(conf)
  super
  @msgpack_formatter = formatter_create(usage: 'formatter_in_example_msgpack', type: 'msgpack')
end

def format(tag, time, record)
  @msgpack_formatter.format(tag, time, record)
end

Plugins using formatter

• filter_stdout
• out_stdout
• out_exec
• out_exec_filter
• out_file
• out_s3

If this article is incorrect or outdated, or omits critical information, please let us know. Fluentd is an open-source project under Cloud Native Computing Foundation (CNCF). All components are available under the Apache 2 License.