Message

Message provides flexible & reliable background/asynchronous job processing mechanism on top of simple queue interface.

Any developer can create queue adapter for Message to hook up different messaging/queue system.

One in-memory queue is included with Message for you to start development and test, and you can easily swap in other queues later.

Installation

Use AWS SQS as back-end queue system

gem 'message-sqs'

How to use

Initialization

Add an initializer config/initializers/message.rb

Message.logger = Rails.logger
# Setup default job queue name, default: "message-worker-default"
Message.worker.default_job = "app-name-#{ENV['MESSAGE_NAMESPACE']}-message-worker-default"
# Bypass queue system and process job synchronously when you called .async
# default: false
Message.worker.sync = !Rails.env.production?
# Change to sqs adapter for asynchronous calls, default is a thread-safe in memory queue named :in_memory
Message.queue.adapter = :sqs

Start worker thread for JRuby in config/initializers/message.rb:

# Start a worker thread in production
if Rails.env.production? && $0 !~ /rake$/
  # Sleep 15 seconds for processed every 10 jobs or less
  # default: size = 10, interval = 5
  Message.worker.start(:size => 10, :interval => 15)
end

Add a rake task for start worker process

namespace :message do
  task :worker do
    Message.worker.start(:size => 10, :interval => 15).join
  end
end

To monitor worker thread events:

Message.worker.callbacks[:start] << lambda {|job_name, options| "start event with options" } Message.worker.callbacks[:crash] << lambda {|job_name, e| "crash event with error" } Message.worker.callbacks[:stop] << lambda {|job_name| "stop event" }

By default, there are event log callbacks installed.

Queuing jobs

Call .async.method(params) on any object and it will be processed in the background.

# without message
@img.resize(36)

# with message
@img.async.resize(36)

The above .async call will enqueue the job to a default job queue (Message.worker.default_job)

Start worker to process default job queue

Message.worker.start

Named job queue

Queuing jobs into speicific queue named 'image-resize-queue':

@img.async('image-resize-queue').resize(36)

Start a worker to process queued jobs:

Message.worker('image-resize-queue').start

Change to synchronize mode

Message.worker.sync = true

This is designed for test environment or Rails development environment. After set the synch option to true, the async jobs will be processed immediately when .async.method(params) is called. The default value is false.

Change default worker job name

For some environment or queue system (e.g. AWS SQS), you will need set an application specific job name, so that you can share same account for multiple applications using Message.

Message.worker.default_job = "app-name-#{Rails.env}-message-default"

Change backend queue system

By change queue adapter:

Message.queue.adapter = :sqs