Make aws signer lib dependent on min ruby version

Author: madebydna

fluent-plugin-kafka.gemspec

@@ -22,7 +22,9 @@ Gem::Specification.new do |gem|
 
   if ENV['USE_RDKAFKA']
     gem.add_dependency 'rdkafka', [ENV['RDKAFKA_VERSION_MIN_RANGE'], ENV['RDKAFKA_VERSION_MAX_RANGE']]
-    gem.add_dependency 'aws-msk-iam-sasl-signer', '~> 0.1.1'
+    if Gem::Version.new('3.0' >= Gem::Version.new(RUBY_VERSION)
+      gem.add_dependency 'aws-msk-iam-sasl-signer', '~> 0.1.1'
+    end
   end
 
   gem.add_development_dependency "rake", ">= 0.9.2"

lib/fluent/plugin/out_rdkafka2.rb

@@ -16,11 +16,14 @@
   elsif rdkafka_version >= Gem::Version.create('0.16.0')
     require_relative 'rdkafka_patch/0_16_0'
   end
-  require 'aws_msk_iam_sasl_signer' if rdkafka_version >= Gem::Version.create('0.16.0')
 rescue LoadError, NameError
   raise "unable to patch rdkafka."
 end
 
+if Gem::Version.create(RUBY_VERSION) >= Gem::Version.create('3.0')
+  require 'aws-msk-iam-sasl-signer'
+end
+
 module Fluent::Plugin
   class Fluent::Rdkafka2Output < Output
     Fluent::Plugin.register_output('rdkafka2', self)