Transaction

Transaction is a small library which helps track the status of running/upcoming tasks. These tasks can be a cron job, background jobs or a simple method. Any task can be plugged into a transaction block.

Transaction uses Redis to store the current status along with the additional attributes(provided during the initialization or transaction update.)

The events within the transaction block can be published via Pubsub client(ex. Pusher, PubNub or any valid pubsub client). These events can be subscribed in the client app for the live status of the transaction.

Requirements

Redis(>=3.0)

Valid Pubsub client if messages need to be published.

Installation

Add this line to your application's Gemfile:

gem 'transaction'

And then execute:

$ bundle

Or install it yourself as:

$ gem install transaction

Usage

Initializing Transaction gem -

In your rails app - create config/transaction.rb

  # Ex. pusher looks like | any pubsub client can be used.
  require 'pusher'
  PubsubClient = Pusher::Client.new(
    app_id:"app_id",
    key: "app_key",
    secret: "app_secret",
    cluster: "cluster_info",
    use_tls: true
  )

  Transaction.configure do |config|
    config.redis = Redis.new # defaults to localhost
    config.pubsub_client = {client: PubsubClient, trigger: 'trigger'}
  end

There's an option to directly connect as well.

  Transaction.redis = Redis.new(url: 'redis://redis_url:6379')
  Transaction.pubsub_client = {client: PubsubClient, trigger: 'trigger'}

The pubsub client accepts the following options -

param	description
client	Any valid pubsub client. Ex. Pusher, PubNub.
trigger	The method name which sends a message to a pubsub client. Ex. 'trigger' for Pusher. 'publish' for PubNub.
channel_name	(Optional) Channel in which the message be published. Defaults to the value of transaction_id.
event	(Optional) Event for which message will be published. Defaults to 'status'

Initializing a transaction

A transaction can be newly initialized or be found with the given transaction_id. If no transaction is found then a new transaction is created.

  attributes = {created_at: Time.now, count: 0 }
  transaction = Transaction::Client.new(options: attributes) # creates a new instance of transaction
  transaction1 = Transaction::Client.new(transaction_id: transaction.transaction_id) # finds the transaction.

Accepted methods for a transaction

The default status of any new transaction is queued. Accepted statuses: ['queued', 'processing', 'success', 'error']. Any transaction at any point will be in one of the states.

method	params	description
start!	-	moves to status processing from queued. Publishes {message: Processing} to pubsub client if enabled.
finish!	(status: 'success', clear: false, data: {})	moves to the passed status (default: success). Any additional data passed is merged with default {message: 'Done}'. clear = true destroy the transaction entry from Redis cache.
clear!	-	destroys the current entry from Redis cache.
refresh!	-	sync current instance transaction with the latest cache (Other instance of a transaction initiated with same transaction id can update the attributes. Hence refresh! is required.).
update_status	status	moves to the passed status. Raises 'Invalid Status' error if the status is not in one of the Accepted statuses defined above.
update_attributes	options = {}	merges the passed options hash to the current attributes object.
trigger_event!	data = {}	publishes the data via pubsub. Current status along with-param data is published(Note: Pubsub client needs to be configured.)

Ex 1: Simple transaction

    def sum_numbers
      arr = (0...10_000).to_a
      options = { created_at: Time.now, total: arr.count  }
      transaction = Transaction::Client.new(options: options)

      transaction.start!
      puts transaction.status # Status moves from `queued` to `processing`

      count = 0
      (1..10_000).each do |i|
        # do some other stuff
        transaction.update_attributes(count: count += 1)
        # do some other stuff
      end

      transaction.finish! # By default moves to status 'success'.

      puts transaction.status # 'success'
      puts transaction.attributes # {:status=>:success, :created_at=>2019-07-19 06:06:43 +0530, :total=>10000, :count=>10000}
    end

Ex 2: Initialize or find a transaction with a transaction id.

    def task1
      transaction = Transaction::Client.new
      SomeWorkerJob.perform_later(transaction.transaction_id) # sidekiq or resque
    end

    class SomeWorkerJob < ApplicationJob
      queue_as :default

      def perform transaction_id
        tr = Transaction::Client.new(transaction_id: transaction_id) # intialize with given transaction_id
        tr.start!

        # do a bunch of stuff
        tr.finish!
      end
    end

Keeping transactions in sync.

Let's say we have 2 transactions t1 and t2 both initialized with the same transaction id. If t2 updates the transaction, then t1 can simply refresh the transaction to get in sync with t2. Note: the transaction will be refreshed with the most recent values. (Versioning transaction updates ??? => Woah that's a nice PR idea.)

  def task1
    transaction = Transaction::Client.new
    transaction.start!
    task2(transaction.transaction_id)

    puts transaction.status # 'processing'
    transaction.refresh!
    puts transaction.status # 'error'
  end

  def task2 transaction_id # in some other context altogether. Task 2 is not at all related to task 1.
    transaction = Transaction::Client.new(transaction_id: transaction_id)
    # do some stuff
    transaction.finish!('error')
  end

Pushing messages to client via pubsub

If a task is running in the background and the client needs to know the status. PubSub can be configured to do so.

   # configure pubsub client as defined above in Initializing Transaction gem

   def long_task
    transaction = Transaction::Client.new
    transaction.start!

    items = (0..10_000).to_a

    items.each do |index|
      transaction.trigger_event!(count: index, total: items.count)
      # do something
    end

    transaction.finish!(data: {count: items.count, total: items.count})
   end

Development

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.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/t2013anurag/transaction. 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.

License

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

Code of Conduct

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