Alchemy Flux

Alchemy-Flux is the Ruby implementation of the Alchemy Micro-Services Framework. Flux is implemented in Ruby using the EventMachine and AMQP gems, these work well with the Alchemy style of communication.

To install Alchemy-Flux:

gem install alchemy-flux

To create instances of two services, A and B, and have instance A1 call service B:

require 'alchemy-flux'

service_a1 = AlchemyFlux::Service.new("A")

service_b1 = AlchemyFlux::Service.new("B") do |message|
  {'body' => "Hello #{message['body']}"}
end

service_a.start
service_b.start

# Synchronous message
response = service_a1.send_request_to_service("B", {'body' => "Alice"})
puts response['body'] # Hello Alice

# Asynchronous message
service_a1.send_request_to_service("B", {'body' => "Bob"}) do |response|
  puts response['body'] # Hello Bob
end

sleep(1) # wait for asynchronous message to complete

service_a.stop
service_b.stop

Alchemy Flux comes with an implementation in Rack so that other popular frameworks like Rails or Sinatra can be used with Alchemy. The main configuration is done through environment variables:

1. ALCHEMY_SERVICE_NAME: the name of the service. REQUIRED
2. AMQ_URI: URL of the RabbitMQ cluster. Default is 'amqp://127.0.0.1',
3. PREFETCH: the number of messages to prefetch from RabbitMQ and handle concurrently. Default is 20.
4. TIMEOUT: the amount of milliseconds the service will wait for outgoing requests. Default is 30000
5. THREADPOOL_SIZE: number of Event Machine Threads, must be greater than PREFETCH and should be as it represents the number of async calls and requests the service can handle. Default is 500
6. ALCHEMY_RESOURCE_PATHS: a comma separated list of resource paths that are handled by this service e.g. '/v1/users,/v1/admins'. Default is ''

Then alchemy-flux gem into a project and run rackup -s alchemy to start the server with Alchemy.

For example, to run a simple Sinatra application in the Alchemy framework you will need the files:

# ./Gemfile
source 'https://rubygems.org'

gem 'sinatra'
gem 'alchemy-flux'

# ./config.ru
ENV['ALCHEMY_SERVICE_NAME'] = 'helloworld.service'
ENV['ALCHEMY_RESOURCE_PATHS'] = '/v1/hello'

require 'alchemy-flux'
require './service'
run Sinatra::Application

# ./service.rb
require 'sinatra'

get '/v1/hello' do
  content_type :json
  {'hello' => 'world!'}.to_json
end

Then run:

bundle install
bundle exec rackup -s alchemy

The service will now be listening on RabbitMQ for incoming messages, running a router and calling over HTTP, or calling directly from another service will be routed to this service.

The documentation for Alchemy Flux is generated by yard.

Example sending a message:

bundle exec ruby examples/example_1_send_message.rb

• Graham Jenson
• Tom Cully
• Andrew Hodgkinson
• Max Dietrich
• Dave Harris