IdempotentBlock

This gem execute passed block by once using database unique key.

class IdempotentExecutor < ApplicationRecord
  #  user_id             :bigint(8)      not null
  #  block_type          :integer(11)    not null
  #  signature           :string(255)    not null
  #  expired_time        :datetime       not null
  #
  # Indexes
  #
  #  unique_index  (user_id, type, signature) UNIQUE

  include IdempotentBlock

  enum block_type: [:post_create]

  register_idempotent_column :user_id, :block_type, :signature
end

exec = IdempotentExecutor.new(user_id: user.id, block_type: :post_create, signature: 'abcdefg')
exec.start do
  user.user_posts.create(params[:new_post])
end

# we don't execute block and raise IdempotentBlock::IdempotentError
exec.start do
  user.user_posts.create(params[:new_post])
end

Installation

Add this line to your application's Gemfile:

gem 'idempotent_block'

And then execute:

$ bundle

Or install it yourself as:

$ gem install idempotent_block

Usage

Basic

exec_1 = IdempotentExecutor.new(user_id: user.id, block_type: :post_create, signature: 'abcdefg')

# first time, we got no error and executed block 
exec_1.finished?
# => false

exec.start do
  user.user_posts.create(params[:new_post])
end

user.user_posts.count
# => 1

exec_1.finished?
# => true

exec_1.executed?
# => true

# second time, we didn't execute block
exec_2 = IdempotentExecutor.new(user_id: user.id, block_type: :post_create, signature: 'abcdefg')
exec_2.finished?
# => true
exec_2.executed?
# => false

exec_2.start do
  user.user_posts.create(params[:new_post])
end

user.user_posts.count
# => 1 we don't execute block

exec_2.finished?
# => true
exec_2.executed?
# => false

Force execute

When you pass force option, we always execute block and update state.

exec.finished?
# => true

exec.start(force: true) do
  user.user_posts.create(params[:new_post])
end

exec.executed?
# => true

Stop execute block

If you raise error in block, we stop execute block and rollback state.

exec.start do
  raise 'error'
end

# when retry, execute block because above block didn't completed
exec.start do
  user.user_posts.create(params[:new_post])
end

Background

exec = IdempotentExecutor.new(user_id: user.id, type: :post_create, signature: 'abcdefg')
exec.start do
  user.user_posts.create(params[:new_post])
end

We use transaction so we rewrite this code like this.

exec = IdempotentExecutor.new(user_id: user.id, type: :post_create, signature: 'abcdefg')

ActiveRecord::Base.transaction do
  user.user_posts.create(params[:new_post])

  begin
    exec.save!
    exec.executed = true
    exec.finished = true
  rescue => ActiveRecord::RecordNotUnique
    exec.finished = true
    exec.executed = false
  end 
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/[USERNAME]/idempotent_block. 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 IdempotentBlock project’s codebases, issue trackers, chat rooms and mailing lists is expected to follow the code of conduct.