PubsubClient

This is a wrapper around the google-cloud-pubsub gem. There are times when it is useful to stub out these resources while in development or test environment. This will allow clients to do just that. Additionally, this gem also handles proper memoization of these resources even in forked and/or multi-threaded environments.

Add this line to your application's Gemfile:

gem 'pubsub_client'

And then execute:

$ bundle install

Or install it yourself as:

$ gem install pubsub_client

In order to use this gem, the environment variable GOOGLE_APPLICATION_CREDENTIALS must be set and point to the credentials JSON file.

If there are environments where setting up credentials is too burdensome and/or publishing messages is not desired, PubsubClient can be stubbed out with .stub!, e.g.

@client = PubsubClient.new

if test_env?
   @client.stub!
end

To publish a message to Pub/Sub, call @client.publish(message, 'the-topic'). This method takes any serializable object as an argument and yields a result object to a block. The result object has a method #succeeded? that returns true if the message was successfully published, otherwise false. In the latter case, there is a method #error that returns the error.

@client.publish(message, 'some-topic') do |result|
  if result.succeeded?
    puts 'yay!'
  else
    puts result.error
  end
end

To subscribe to a topic, a client must first get a handle to the subscriber object. After doing so, a call to subscriber.listener will yield two arguments: the data (most clients will only need this) and the full Pub/Sub message (for anything more robust). Documentation for the full message can be found here.

Optionally, a client can choose to handle exceptions raised by the subscriber. If a client chooses to do so, the listener must be configured before on_error since the latter needs a handler to the underlying listener. Additionally, exceptions will only be raised when the work inside the block is happening on the same thread. For instance, if the block enqueues a background worker and that worker raises an error, it will not be handled by the on_error block.

subscriber = @client.subscriber('some-subscription')

subscriber.listener(concurrency: 4, auto_ack: false) do |data, received_message|
  # Most clients will only need the first yielded arg.
  # It is the same as calling received_message.data
end

# Optional
subscriber.on_error do |ex|
  # Do something with the exception.
end

subscriber.subscribe # This will sleep

By default, the underlying subscriber will use a concurrency of 8 threads and will acknowledge all messages. If these defaults are acceptable to the client, no arguments need to be passed in the call to listener.

subscriber.listener do |data, received_message|
  # Do something
end

After checking out the repo, run bin/setup to install dependencies. Then, run rake spec to run the tests. You can also 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 contribute, open a pull request against main. Note that once your changes have been made, you should not manually modify the version.rb or CHANGELOG as these will get updated automatically as part of the release process.

To release a new version, after you have merged your changes into main:

1. Run the gem-release script. This can be found here.

   path/to/gem-release [major/minor/patch] "Short message with changes"
   

   Note that the Short message with changes is what gets reflected in the releases of the repo.
2. Run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org. This step will update the version.rb and CHANGELOG files.

Bug reports and pull requests are welcome on GitHub at https://github.com/[USERNAME]/pubsub_client. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the code of conduct.

The gem is available as open source under the terms of the MIT License.

Everyone interacting in the PubsubClient project's codebases, issue trackers, chat rooms and mailing lists is expected to follow the code of conduct.