PubSub code sample

About

A code sample app which implements the pub/sub model.

Preliminary requirements

You may want to install Redis and run redis-server with the default local settings.

Usage

Broker

• Run redis-server

We need Redis for message persistence so each subscriber receives the recent messages from the last 30 minutes on established connection with the broker.

• Two ways to propel the central broker:
  • PubSubRedis::Broker.new.run
  • bundle exec rake ps:broker

The aforementioned rake task uses the default development configuration - localhost:20000.

By default PubSubRedis::Broker has a dependency injection of PubSubRedis::LocationTuple which evaluates to the tuple (localhost, 20_000) if nothing else is mentioned.

Subscribers

Subscripe to particular topics

For the purposes of flexibility, several ways to instantiate a subscriber are possible.

A simple DSL is defined for convenience and bulk topic subscription.

listener = PubSubRedis::Subscriber.new do |subscriber|
  subscriber.enroll 'cars'
  subscriber.enroll 'money'
  subscriber.enroll 'girls'
end

listener.topics # => ['cars', 'money', 'girls']

Single topic can also be subscribed by:

listener.enroll('food')

listener.topics # => ['cars', 'money', 'girls', 'food']

Duplicative topics get rejected.

listener.enroll('grils')

listener.topics # => ['cars', 'money', 'girls', 'food']

By default PubSubRedis::Subscriber accepts a PubSubRedis::LocationTuple which evaluates to (localhost, 20_000) if nothing else is mentioned.

Listen

Invoke the method PubSubRedis::Subscriber#listen

listener.listen

Now this subscriber is listening from the central broker for new messages. It also gets the recent messages from the last 30 minutes on an established connection.

listener.listen do |message|
  # make something with message
  something = 1 + 1
  puts "[#{something}] MODIFIED MESSAGE #{message}"
end

Sample subscribers

Sample could be executed by the following rake tasks:

• bundle exec rake ps:subscriber_one Subscribed for topics: cars, money, girls

• bundle exec rake ps:subscriber_two Subscribed for topics: money

Publisher

Invoke PubSubRedis::Publisher#execute to send messages to the central broker.

publisher = PubSubRedis::Publisher.new

publisher.execute(topic: 'money', body: 'lorem ipsum dollor')

Sample publisher

Sample could be executed by the following rake task:

• bundle exec rake ps:publisher

Sample CLI Chat

A sample chat is implemented by the means of this gem.

start the broker:

1. redis-server
2. bundle exec rake ps:broker

start chat client (two times)

bundle exec rake ps:chat