# Rdkafka

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The `rdkafka` gem is a modern Kafka client library for Ruby based on
[librdkafka](https://github.com/edenhill/librdkafka/).
It wraps the production-ready C client using the [ffi](https://github.com/ffi/ffi)
gem and targets Kafka 0.10+ and Ruby 2.1+.

This gem only provides a high-level Kafka consumer. If you are running
an older version of Kafka and/or need the legacy simple consumer we
suggest using the [Hermann](https://github.com/reiseburo/hermann) gem.

## Installation

This gem downloads and compiles librdkafka when it is installed. If you
have any problems installing the gem please open an issue.

## Usage

See the [documentation](http://www.rubydoc.info/github/thijsc/rdkafka-ruby/master) for full details on how to use this gem. Two quick examples:

### Consuming messages

```ruby
config = {
  :"bootstrap.servers" => "localhost:9092",
  :"group.id" => "ruby-test"
}
consumer = Rdkafka::Config.new(config).consumer
consumer.subscribe("ruby-test-topic")

consumer.each do |message|
  puts "Message received: #{message}"
end
```

### Producing messages

```ruby
config = {:"bootstrap.servers" => "localhost:9092"}
producer = Rdkafka::Config.new(config).producer

100.times do |i|
  puts "Producing message #{i}"
  producer.produce(
      topic:   "ruby-test-topic",
      payload: "Payload #{i}",
      key:     "Key #{i}"
  ).wait
end
```

## Development

For development we expect a local zookeeper and kafka instance to be
running. Run `bundle` and `cd ext && bundle exec rake && cd ..`. Then
create the topics as expected in the specs: `bundle exec rake create_topics`.

You can then run `bundle exec rspec` to run the tests. To see rdkafka
debug output:

```
DEBUG_PRODUCER=true bundle exec rspec
DEBUG_CONSUMER=true bundle exec rspec
```

To see everything working run these in separate tabs:

```
bundle exec rake consume_messages
bundle exec rake produce_messages
```