Fix issues revealed in test setup; Add fork info to README

Gemfile

@@ -3,4 +3,5 @@ source 'https://rubygems.org'
 # Specify your gem's dependencies in fluent-plugin-kafka.gemspec
 gemspec
 
+gem 'json', '2.7.3' # override of 2.7.4 version
 gem 'rdkafka', ENV['RDKAFKA_VERSION_MIN_RANGE'], ENV['RDKAFKA_VERSION_MAX_RANGE'] if ENV['USE_RDKAFKA']

README.md

@@ -29,6 +29,45 @@ If you want to use zookeeper related parameters, you also need to install zookee
 
 ## Usage
 
+### :exclamation: In this fork: MSK IAM Authentication Support for `rdkafka2` Output Type
+
+This fork adds support for using MSK IAM authentication with the `rdkafka2` output type in Fluentd. Authentication and authorization with an MSK cluster are facilitated through a base64-encoded signed URL, which is generated by the [aws-msk-iam-sasl-signer-ruby](https://github.com/bruce-szalwinski-he/aws-msk-iam-sasl-signer-ruby) library.
+
+The `aws-msk-iam-sasl-signer-ruby` library provides an [example](https://github.com/bruce-szalwinski-he/aws-msk-iam-sasl-signer-ruby/tree/main/examples/rdkafka) for generating the OAuthBearer token using rdkafka, which is one of the core Kafka libraries supported by the Fluentd fluent-plugin-kafka plugin. This fork integrates that example into the `Fluent::Rdkafka2Output` class, enabling AWS IAM authentication.
+
+The key change is the inclusion of a refresh callback:
+```ruby
+Rdkafka::Config.oauthbearer_token_refresh_callback = method(:refresh_token)
+```
+This callback triggers token generation when needed, ensuring continuous authentication with the MSK cluster.
+
+#### Configuration Example
+To enable this feature, configure your Fluentd input as follows:
+
+```
+<match *>
+    @type rdkafka2
+    # Kafka brokers to connect to (typically port 9098 or 9198 for IAM authentication)
+    brokers <broker_addresses>
+    # Topic to write events to
+    topic_key test-topic-1
+    default_topic test-topic-1
+
+    # AWS Region (required)
+    aws_msk_region us-east-1
+
+    # Use a shared producer for the connection (required)
+    share_producer true
+
+    # MSK IAM authentication settings (required)
+    rdkafka_options {
+      "security.protocol": "sasl_ssl",
+      "sasl.mechanisms": "OAUTHBEARER"
+    }
+</match>
+```
+With this configuration, Fluentd will handle the token refresh and manage the connection to your MSK cluster using AWS IAM authentication.
+
 ### Common parameters
 
 #### SSL authentication
@@ -563,7 +602,7 @@ You need to install rdkafka gem.
     </match>
 
 `rdkafka2` supports `discard_kafka_delivery_failed_regex` parameter:
-- `discard_kafka_delivery_failed_regex` - default: nil - discard the record where the Kafka::DeliveryFailed occurred and the emitted message matches the given regex pattern, such as `/unknown_topic/`. 
+- `discard_kafka_delivery_failed_regex` - default: nil - discard the record where the Kafka::DeliveryFailed occurred and the emitted message matches the given regex pattern, such as `/unknown_topic/`.
 
 If you use v0.12, use `rdkafka` instead.
 

fluent-plugin-kafka.gemspec

@@ -21,7 +21,6 @@ Gem::Specification.new do |gem|
   gem.add_dependency 'ruby-kafka', '>= 1.5.0', '< 2'
   gem.add_dependency 'rdkafka'
   gem.add_dependency 'aws-msk-iam-sasl-signer'
-  gem.add_dependency 'json', '2.7.3'
   gem.add_development_dependency "rake", ">= 0.9.2"
   gem.add_development_dependency "test-unit", ">= 3.0.8"
   gem.add_development_dependency "test-unit-rr", "~> 1.0"

lib/fluent/plugin/out_rdkafka2.rb

@@ -4,6 +4,7 @@
 require 'fluent/plugin/kafka_plugin_util'
 
 require 'rdkafka'
+require 'aws_msk_iam_sasl_signer'
 
 begin
   rdkafka_version = Gem::Version::create(Rdkafka::VERSION)
@@ -307,8 +308,14 @@ def build_config
     end
 
     def refresh_token(_config, _client_name)
-      print "refreshing token\n"
+      log.info("+--- Refreshing token")
       client = get_producer
+      # This will happen once upon initialization and is expected to fail, as the producer isnt set yet
+      # We will set the token manually after creation and after that this refresh method will work
+      unless client
+        log.info("Could not get shared client handle, unable to set/refresh token (this is expected one time on startup)")
+        return
+      end
       signer = AwsMskIamSaslSigner::MSKTokenProvider.new(region: @aws_msk_region)
       token = signer.generate_auth_token
 
@@ -325,18 +332,21 @@ def refresh_token(_config, _client_name)
       end
     end
 
-    # HERE -----------------
     def start
       if @share_producer
         @shared_producer = @rdkafka.producer
+        log.info("Created shared producer")
+        if @aws_msk_region
+          refresh_token(nil, nil)
+          log.info("Set initial token for shared producer")
+        end
       else
         @producers = {}
         @producers_mutex = Mutex.new
       end
 
       super
     end
-    # HERE -----------------
 
     def multi_workers_ready?
       true