README.md in caerbannog-0.1.0 vs README.md in caerbannog-0.2.0
- old
+ new
@@ -1,10 +1,11 @@
# Caerbannog
+[](https://circleci.com/gh/magplus/caerbannog)
-Welcome to your new gem! In this directory, you'll find the files you need to be able to package up your Ruby library into a gem. Put your Ruby code in the file `lib/caerbannog`. To experiment with that code, run `bin/console` for an interactive prompt.
+Implements a database buffer and workers for sending and receiving events
+to/from RabbitMQ.
-TODO: Delete this and the text above, and describe your gem
## Installation
Add this line to your application's Gemfile:
@@ -20,16 +21,90 @@
$ gem install caerbannog
## Usage
-TODO: Write usage instructions here
+The gem is meant to be used by a sender application and one or more receiver
+applications.
+### On the sender side
+
+Caerbannog needs to be configured with a message storage class that is an
+ActiveRecord model or works like an ActiveRecord model with regards to the
+methods `.all`, `.create!` and `#destroy`, and has two attributes `name` and
+`payload`. It also needs a RabbitMQ read and a write URL.
+
+```ruby
+Caerbannog.configure do |config|
+ config.message_class = MessageQueueMessage
+ config.rabbit_read_url = ENV['RABBIT_URL']
+ config.rabbit_write_url = ENV['RABBIT_URL']
+end
+```
+
+If you are using the gem from within a Rails application, you can run the
+following to generate this model and the configuration:
+
+ $ rails generate caerbannog
+
+This generates a migration file, an ActiveRecord message class
+`MessageQueueMessage`, and an initializer file.
+
+This class will be used to store messages when you call
+`Caerbannog::Queue.push`, before they are sent to RabbitMQ,
+
+Call the `Caerbannog::Queue.push` method with two parameters: the message name,
+that will be used as the routing key in RabbitMQ, and the message payload,
+which should be a hash or an array.
+
+```ruby
+Caerbannog::Queue.push('message name', { one_field: 'one', two_field: 'two' })
+```
+
+We then need a background publisher that uses the `all` method of the message
+class to fetch all pushed messages and send them to RabbitMQ, and then
+`destroy`s them.
+
+If you have initialized the `Caerbannog::Queue#message_class=`, you can use
+something like this to start the publisher process:
+
+ $ bundle exec rails runner 'Caerbannog::Queue.publish'
+
+### On the receiving side
+
+To receive messages you need to run a subscriber process that calls the
+`Caerbannog::Queue.subscribe` method. An example subscriber class with some
+error handling might look like this:
+
+```ruby
+class MessageQueueWorker
+ def perform
+ Caerbannog::Queue.subscribe('my-apps-queue-name', 'message-name1', 'message-name2') do |delivery_info, properties, payload|
+ parsed_message = JSON.parse(payload)
+ # Do something with the parsed message
+ end
+ rescue Bunny::TCPConnectionFailedForAllHosts => e
+ puts 'Oh no' # Handle the error somehow
+ sleep 10 # Wait for RabbitMQ to come back up
+ retry # Try to reconnect
+ end
+end
+```
+
+and you might run this process like
+
+ $ bundle exec rails runner 'MessageQueueWorker'
+
## Development
-After checking out the repo, run `bin/setup` to install dependencies. Then, run `bin/console` for an interactive prompt that will allow you to experiment.
+After checking out the repo, run `bin/setup` to install dependencies. Then, run
+`bin/console` for an interactive prompt that will allow you to experiment.
-To install this gem onto your local machine, run `bundle exec rake install`. To release a new version, update the version number in `version.rb`, and then run `bundle exec rake release` to create a git tag for the version, push git commits and tags, and push the `.gem` file to [rubygems.org](https://rubygems.org).
+To install this gem onto your local machine, run `bundle exec rake install`. To
+release a new version, update the version number in `version.rb`, and then run
+`bundle exec rake release` to create a git tag for the version, push git
+commits and tags, and push the `.gem` file to
+[rubygems.org](https://rubygems.org).
## Contributing
1. Fork it ( https://github.com/[my-github-username]/caerbannog/fork )
2. Create your feature branch (`git checkout -b my-new-feature`)