Replicate data across your applications
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README.md

Synapse

This repository contains the code used in the following paper:

Synapse: A Microservices Architecture for Heterogeneous-Database Web Applications

The paper can be downloaded here: http://viennot.com/synapse.pdf

The slides can be found here: http://viennot.com/synapse-slides.pdf

The slides with speaker notes can be found here: http://viennot.com/synapse-slides-notes.pdf

The code

Synapse was renamed from the original name Promiscuous, but in the code, the original name remains.

Synapse's behavior is specified in its test suite: ./spec/integration.

If you are curious about the publishing algorithm, most of it is in here: ./lib/promiscuous/publisher/operation/base.rb.

Rails Quick Tutorial

1. Preparation

We need a few things for the synapse tutorial:

  • The AMQP broker RabbitMQ up and running.
  • The key-value storage system Redis (at least 2.6) up and running.
  • Both applications must be running on separate databases.
  • Both applications must have a User model with two attributes name and email.

2. Publishing

By including the Promiscuous publisher mixin, we can publish the model attributes:

# app/models/user.rb on the publisher app
class User
  include Promiscuous::Publisher
  publish :name, :email
end

3. Subscribing

Similarly to the publisher app, we can subscribe to the attributes:

# app/models/user.rb on the subscriber app
class User
  include Promiscuous::Subscriber
  subscribe :name, :email

  after_create { Rails.logger.info "Hi #{name}!" }
end

4. Replication

The subscriber must listen for new data to arrive. Launch the subscriber with the following command:

bundle exec promiscuous subscribe

You should start the subscriber first, otherwise the appropriate queues will not be created. From now on, you should see the queue in the RabbitMQ web admin page. Create a new user in the publisher's Rails console with:

User.create(:name => 'Yoda')`

You should see the message "Hi Yoda!" appearing in the log file of the subscriber.

License

LGPL.