Surety

A lightweight guaranteed-delivery messaging system.

Dependency Notes

Surety uses ActiveRecord to persist the message requests in order to provide transactional, guaranteed-delivery requests. Requires ActiveRecord 3.0.0 or higher.
Surety uses Resque to underpin the message processing/retry loop. Requires Resque 1.19.0 or higher.

Usage / Examples

A simple class that can send a message for guaranteed delivery:

class TestGenerator
  include Surety::Generator

  def some_method
    self.send_message(message_content)
  end
end

On the server side, to start up the loop to process messages:

Surety::Processor.request_next

Configuration

Both the prefix for the ActiveRecord database connection name (as specified in database.yml) and the class to which Surety delegates messages for processing after pulling them off the queue are configurable.

Also configurable are three parameters related to failure retries:

retry interval: base amount of time to wait before a retry, in minutes. Defaults to 10.
backoff factor: factor to divide the failure count by before calculating an exponential backoff. The backoff factor is (2^floor(failure count/backoff interval)). Defaults to 2.
max backoff: maximum number of powers of 2 to backoff. Defaults to 7 (which gives a backoff factor of 128; together with the default retry interval of 10, this produces a default max backoff amount of 1280 minutes ~ 1 day).

Example configuration (from a sample config/initializers/surety.rb file)

Surety::Configuration.database_prefix = 'surety_'
Surety::Configuration.message_processing_delegate = MessageDistributor
Surety::Configuration.retry_interval = 20
Surety::Configuration.backoff_factor = 4
Surety::Configuration.max_backoff = 5

Install

As a gem

$ gem install surety

Acknowledgements

Thanks to Ryan and Steve for arguing that this gem was necessary... it is.