Awesome
Hermann
A Ruby gem implementing a Kafka Publisher and Consumer
On MRI (C-based Ruby), this library wraps the librdkafka library which is implemented in C.
On JRuby this library declares jar
dependencies
inside the .gemspec
to express dependencies on the Java-based Kafka library
provided by the Kafka project. Tools like
jbundler will handle these
declarations correctly.
Usage
Usage is modelled on the kafka-rb gem and is fairly straightforward.
- Kafka 0.8 is supported.
- Ruby 1.9.3, 2.1.1 and JRuby are tested against
Producer
Zookeeper discovery
Discover Kafka brokers through zookeeper. Looks at /brokers/ids
in Zookeeper to find the list of brokers.
require 'hermann/producer'
require 'hermann/discovery/zookeeper'
broker_ids_array = Hermann::Discovery::Zookeeper.new('localhost:2181').get_brokers
producer = Hermann::Producer.new('topic', broker_ids_array)
promise = producer.push('hello world') # send message to kafka
promise.value # forces the Concurrent::Promise to finish excuting (#value!)
promise.state # the state of the promise
MRI only
require 'hermann/producer'
broker_ids_array = Hermann::Discovery::Zookeeper.new('localhost:2181').get_brokers
p = Hermann::Producer.new('topic', broker_ids_array) # arguments topic, list of brokers
f = p.push('hello world from mri')
f.state
p.tick_reactor
f.state
Consumer
Messages can be consumed by calling the consume method and passing a block to handle the yielded messages. The consume method blocks, so take care to handle that functionality appropriately (i.e. use Concurrent::Promise, Thread, etc).
(JRuby)
require 'hermann'
require 'hermann/consumer'
require 'hermann_jars'
topic = 'topic'
new_topic = 'other_topic'
the_consumer = Hermann::Consumer.new(topic, zookeepers: "localhost:2181", group_id: "group1")
the_consumer.consume(new_topic) do |msg| # can change topic with optional argument to .consume
puts "Recv: #{msg}"
end
(MRI)
MRI currently has no zookeeper / client group support.
require 'hermann'
require 'hermann/consumer'
topic = 'topic'
new_topic = 'other_topic'
the_consumer = Hermann::Consumer.new(topic, brokers: "localhost:9092", partition: 1)
the_consumer.consume(new_topic) do |msg, key, offset| # can change topic with optional argument to .consume
puts "Recv: #{msg}, key: #{key}, offset: #{offset}"
end
Metadata request (MRI-only)
Topic and cluster metadata may be retrieved in the MRI version by querying the Kafka brokers.
require 'hermann'
require 'hermann/discovery/metadata'
c = Hermann::Discovery::Metadata.new( "localhost:9092" )
topic = c.topic("topic")
puts topic.partitions.first
consumers = topic.partitions.map do |partition|
partition.consumer
end
Build & Unit Test
First time (from a clean repository):
bundle install && bundle exec rake
Thereafter:
bundle exec rake spec
Testing
To run the integration tests:
- startup your own instance of zookeeper/kafka
rspec spec/integration/producer_spec.rb
How to convert from using jruby-kafka
- Gemfile
- remove jruby-kafka
- add
gem "hermann"
bundle install
- Jarfile
- removed unecessary jars from your Jarfile (i.e. kafka, log4j)
- jar dependencies are automatically included with Hermann
jbundle install
- Test out one of the Producer/Consumer examples above