HeyYou

Use postgres to LISTEN/NOTIFY to trigger custom events.

Let's say you've got a fleet of machines running code, you only want to trigger a custom event on all of them or one of them. With HeyYou it is super easy. What kind of event? Maybe it is for debugging or maybe it is for housekeeping. For example you could take a heap dump off of a running server and upload it to S3 using this library.

Add this line to your application's Gemfile:

gem 'hey_you'

And then execute:

$ bundle

Or install it yourself as:

$ gem install hey_you

Somewhere in your code you can run:

HeyYou.new.listen do |payload|
  puts "Hey I got a message: #{payload}"
end

This will spin up a new thread and periodically check for a notification, this won't block execution by default.

Then in another console, you can run:

HeyYou.new.notify("sup")

When your listening process gets the message it will print out

"Hey I got a message: sup"

By default all listens and notifies happen on the same channel. If you want you can specify a different channel

HeyYou.new(channel: "new_channel_name").listen do |payload|
  puts "Hey I got a message: #{payload}"
end

It is important to note that you need to notify against the same name.

HeyYou.new(channel: "new_channel_name").notify("sup")

By default the background thread wakes up every 60 seconds and waits 0.1 seconds to see if there is a message. You can customize this behavior using sleep and ttl. So to have it check every 10 seconds, and not wait at all you could run

HeyYou.new(ttl: 1, sleep: 10).listen do |payload|
  puts "Hey I got a message: #{payload}"
end

A lower sleep will decrease delay between sending and receiving messages but will decrease overall program performance.

By default HeyYou assumes you're using Active Record and already have a connection configured. If you want to use a different ORM, you'll need to provide HeyYou with an object that responds to exec that executes arbitrary SQL and a method wait_for_notify that accepts ttl, sleep and takes a block.

You can configure your connection manually

HeyYou.new(connection: my_custom_object)

Or you can set it globally

HeyYou::DEFAULT_CONNECTION = my_custom_object

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 release a new version, update the version number in version.rb, and then 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.

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

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