Kafka::Retryable

Consumer failures are common for Kafka consumers, and if these are left unhandled, it can lead to data losses. There are many ways to buffer and retry messages that encounter failures. The aim of kafka-retryable is to provide multiple types of failure handling policies that can be used depending on the need.

Installation

Add this line to your application's Gemfile:

gem 'kafka-retryable'

And then execute:

$ bundle

Or install it yourself as:

$ gem install kafka-retryable

Usage

kafka_retryable allows failed messages to be buffered into a dead_letter_queue inside Kafka. In the future, it will provision for retry mechanisms and the ability to buffer in other messaging systems.

1. Setup the gem by setting configuration parameters. In a rails project, this can be done inside config/initializers/kafka_retryable.rb for instance:

 Kafka::Retryable.setup do |config|
   config.failure_handling.enabled = true
   config.buffer.kafka.seed_brokers = ['kafka://localhost:9092']
 end

These are the available configurations:

Option	Value type	Description	Default
failure_handling.enabled	Boolean	Set if buffering failed messages to a topic in Kafka is enabled	true
buffer.kafka.seed_brokers	Array	Kafka broker URL. Example: kafka://127.0.0.1:9092 or kafka+ssl://127.0.0.1:909	nil

1. Start with declaring configuration parameters for your class using the following syntax:

Class KafkaConsumer
  include Kafka::Retryable::HandleFailure

  configure_handler buffer: :kafka, 
                    dead_letter_queue: :topic_t1, 
                    exception_blacklist: [Karafka::InvalidMessageError],
                    after_failure: ->(error, message) { Bugsnag.notify("#{error}-#{message}") }

  def consume
    # Message consumption logic goes here
  end
end

• dead_letter_queue: Topic where the consumer should enqueue the failure message.
• exception_blacklist: List of exception classes for which the error handling logic does not apply
• exception_whitelist: List of exception classes for which the error handling logic should apply
• after_failure: Accepts a proc that is executed after failure handling is completed

If exception_blacklist and exception_whitelist are both missing, then the error handling logic will apply for all exception classes.

1. Enclose message processing logic inside handle_failure(message) helper method provided by kafka-retryable

handle_failure(message) do
  MessageProcessor.new(message).perform
end

Overall, this is how Kafka Consumers using kafka-retryable will look like:

Class KafkaConsumer
  include Kafka::Retryable::HandleFailure

  configure_handler buffer: :kafka, 
                    dead_letter_queue: :topic_t1, 
                    exception_blacklist: [Karafka::InvalidMessageError],
                    after_failure: ->(error, message) { Bugsnag.notify("#{error}-#{message}") }

  def consume
    handle_failure(message)
      # Message consumption logic goes here
    end
  end
end

kafka-retryable will make sure any exceptions outside the exception_blacklist will cause the message to be enqueued into the dead_letter_queue specified in the failure_handler configuration.

Development

After checking out the repo, run bin/setup to install dependencies. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/[USERNAME]/kafka-retryable. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Contributor Covenant code of conduct.

License

The gem is available as open source under the terms of the MIT License.

Code of Conduct

Everyone interacting in the Kafka::Retryable project’s codebases, issue trackers, chat rooms and mailing lists is expected to follow the code of conduct.