propono

Propono

Propono is a pub/sub gem built on top of Amazon Web Services (AWS). It uses Simple Notification Service (SNS) and Simple Queue Service (SQS) to seamlessly pass messages throughout your infrastructure.

It's beautifully simple to use. Watch an introduction

# On Machine A
Propono::Client.new.listen('some-topic') do |message|
  puts "I just received: #{message}"
end

# On Machine B
Propono::Client.new.publish('some-topic', "The Best Message Ever")

# Output on Machine A a second later.
# - "I just received The Best Message Ever"

Upgrading

Upgrades from v1 to v2, and v2 to v3 are covered in the upgrade documentation.

Installation

Add this line to your application's Gemfile:

gem 'propono'

And then execute:

$ bundle install

Usage

The first thing to do is setup some configuration for Propono. It's best to do this in an initializer, or at the start of your application. If you need to setup AWS authentication, see the AWS Configuration section.

client = Propono::Client.new

You can then start publishing messages easily from anywhere in your codebase.

client = Propono::Client.new
client.publish('some-topic', "Some string")
client.publish('some-topic', {some: ['hash', 'or', 'array']})

Listening for messages is easy too. Just tell Propono what your application is called and start listening. You'll get a block yielded for each message.

client = Propono::Client.new
client.config.application_name = "application-name" # Something unique to this app.
client.listen('some-topic') do |message|
  # ... Do something interesting with the message
end

In the background, Propono is automatically setting up a queue using SQS, a notification system using SNS, and gluing them all together for you. But you don't have to worry about any of that.

Does it matter what I set my application_name to? For a simple publisher and subscriber deployment, no. However, the application_name has a direct impact on subscriber behaviour when more than one is in play. This is because a queue is established for each application_name/topic combination. In practice:

• subscribers that share the same application_name will act as multiple workers on the same queue. Only one will get to process each message.
• subscribers that have a different application_name will each get a copy of a message to process independently i.e. acts as a one-to-many broadcast.

AWS Configuration

By default, Propono will create SQS and SNS clients with no options. In the absence of options, these clients will make use of the credentials on the current host. See the AWS SDK For Ruby Configuration documentation for more details.

To manually configure options for use with AWS, use aws_options, which sets options to be passed to both clients. For example:

client = Propono::Client.new do |config|
  config.aws_options = {
    region:            'aws_region',
    access_key_id:     'your_access_key_id',
    secret_access_key: 'your_secret_access_key'        
  }
end

In addition to this, there are also sqs_options and sns_options, used to configure each client independently. See the SQS Client and SNS Client documentation for available options. These individual options are merged with aws_options with the per-client options taking precendence.

General Configuration

Propono::Client.new do |config|
  # AWS Configuration, see above.
  config.aws_options = {...}
  config.sqs_options = {...}
  config.sns_options = {...}

  config.application_name = "A name unique in your network"
  config.logger = "A logger such as Log4r or Rails.logger"

  config.max_retries = "The number of retries if a message raises an exception before being placed on the failed queue"
  config.num_messages_per_poll = "The number of messages retrieved per poll to SQS"

  config.slow_queue_enabled = true
end

Options

Async

By default messages are posted inline, blocking the main thread. The async: true option can be sent when posting a message, which will spawn a new thread for the message networking calls, and unblocking the main thread.

Visiblity Timeout

For certain tasks (e.g. video processing), being able to hold messages for longer is important. To achieve this, the visibility timeout of a message can be changed on the call to listen. e.g.

client.listen('long-running-tasks', visiblity_timeout: 3600) do |message|
  puts "I just received: #{message}"
end

Slow Queue

The slow queue can be disabled by setting slow_queue_enabled to false. This will yield performance improvements if you do not make use of the "slow queue" functionality.

Is it any good?

Yes.

Contributing

Firstly, thank you!! :heart::sparkling_heart::heart:

We'd love to have you involved. Please read our contributing guide for information on how to get stuck in.

Contributors

This project is managed by the Jeremy Walker.

These individuals have come up with the ideas and written the code that made this possible:

• Jeremy Walker
• Malcolm Landon
• Charles Care
• Rob Styles

Licence

Copyright (C) 2017 Jeremy Walker

This program is free software: you can redistribute it and/or modify it under the terms of the MIT License.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the MIT License for more details.

A copy of the MIT License is available in LICENCE.md along with this program.