This mixin is to prepend to 3rd party plugins of v0.12 APIs. 3rd party plugins may override default values of some parameters, like `buffer_type`. But default values of such parameters will NOT used, but defaults of <buffer>@type</buffer> will be used in fact. It should bring troubles. This mixin defines Class method .config_param and .config_set_default (which should be used by extend) to propagate changes of default values to subsections.
# File lib/fluent/compat/propagate_default.rb, line 28 def self.included(mod) mod.extend(ClassMethods) end