🔥 A pub-sub framework built on Kafka

Proof-of-concept, so you probably shouldn’t use it in production

First, install Kafka. With Homebrew, use:

brew install kafka
brew services start zookeeper
brew services start kafka

Add this line to your application’s Gemfile:

gem "wire", github: "ankane/wire"

Publish a message with:

Wire.publish(:visit, {name: "McNulty"})

Create a new consumer with:

rails generate wire:consumer Welcome

It’ll be placed in app/consumers. Update it to:

class WelcomeConsumer < Wire::Consumer
  topic :visit

  def perform(message)
    puts "Hi #{message["name"]}"
  end
end

Run consumers with:

bundle exec wire

Publish model updates from one app

class User < ActiveRecord::Base
  publish :name, :email
end

And subscribe in another app (start consumers as normal)

class User < ActiveRecord::Base
  subscribe :name, :email
end

To sync all records, use:

User.find_each { |user| user.sync }

To make development easier, you can run consumers immediately with:

WelcomeConsumer.perform_now(message)

To consume a single message, use:

WelcomeConsumer.consume_once

Use the metadata method to access info like partition, offset, key, and raw value.

class WelcomeConsumer < Wire::Consumer
  def perform(message)
    metadata[:partition]
    metadata[:offset]
    metadata[:key]
    metadata[:value]
  end
end

By default, Wire uses JSON for serialization.

To disable serialization, use:

Wire.default_serializer = :noop

For MessagePack, add msgpack to your Gemfile and use:

Wire.default_serializer = :msgpack

Or create a custom serializer

class CustomSerializer
  def serialize(data)
    data + "!!!"
  end

  def deserialize(data)
    data.chomp("!!!")
  end
end

Wire.register_serializer(:custom, CustomSerializer, default: true)

You can also specify a serializer when publishing

Wire.publish(topic, message, serializer: :msgpack)

Or consuming

class MessageConsumer < Wire::Consumer
  serializer :msgpack
end

• Multi-threaded consumers
• Auto-reload consumers
• Connection pool for publish
• Hooks for instrumentation
• Ability to disable consumers
• Retries

Thanks to Promiscuous for designing a great interface for model updates.