WorkerTools

WorkerTools is a collection of modules meant to speed up how we write background tasks following a few basic patterns. The structure of plain independent modules with limited abstraction allows to define and override a few methods according to your needs without requiring a deep investment in the library.

These modules provide some features and conventions to address the following points with little configuration on your part:

• How to save the state the task.
• How to save information relevant to the admins / customers.
• How to log the details
• How to handle exceptions and send notifications
• How to process CSV files (as input and output)
• How to process XLXS files (as input, output coming next)
• How to set options

Installation

Add this line to your application's Gemfile:

gem 'worker_tools'

And then execute:

$ bundle

Or install it yourself as:

$ gem install worker_tools

Conventions

Most of the modules require an ActiveRecord model to keep track of the state, information, and files related to the job. The class of this model is typically an Import, Export, Report.. or something more generic like a JobEntry.

An example of this model for an Import using Paperclip would be something like this:

class Import < ApplicationRecord
  enum state: { waiting: 0, complete: 1, failed: 2 }
  enum kind: { foo: 0, bar: 1 }

  has_attached_file :attachment

  validates :kind, presence: true
  validates :state, presence: true
  end

The state complete and failed are used by the modules. Both state and kind could be an enum or just a string field. Whether you have one, none or many attachments, and which library you use to handle it's up to you.

In this case the migration would be something like this:

  def change
    create_table :imports do |t|
      t.integer :kind, null: false
      t.integer :state, default: 0, null: false
      t.text :information
      t.json  :options, default: {}

      t.string :attachment_file_name
      t.integer :attachment_file_size
      t.string :attachment_content_type

      t.timestamps
    end

Module 'Basics'

the basics module takes care of finding or creating the model, marking it as completed or failed, and calling any flow control wrappers around run that had been specified. (See wrappers)

A simple example would be as follows:

class MyImporter
  include WorkerTools::Basic
  wrappers :basics

  def model_class
    Import
  end

  def model_kind
    'foo'
  end

  def run
    # do stuff
  end
end

The basics module contains a perform method, which is the usual entry point for ApplicationJob and Sidekiq. It can receive the id of the model, the model instance, or nothing, in which case it will attempt to create this model on its own.

Module 'Recorder'

Provides some methods to manage a log and the information field of the model. The main methods are add_info, add_log, and record (which both logs and appends the message to the information field). See all methods in recorder

This module has a recoder wrapper that will register the exception details into the log and information field in case of error:

class MyImporter
  include WorkerTools::Basic
  wrappers :basics, :recorder
  # ...
end

If you only want the logger functions, without worrying about persisting a model, you can use the logger wrapper and include the module as a stand alone component (without the basics module), like this:

  class StandAloneWithLogging
    include WorkerTools::Recorder

    def perform
      with_wrapper_logger do
        # do stuff
      end
    end
  end

Module RocketchatErrorNotifier

recorder

Module CSV Input

csv_input

Module CSV Output

csv_output

Module XLSX Input

xlsx_input

Wrappers

In the basics module, perform calls your custom method run to do the actual work of the task, and wraps it around any methods expecting a block that you might have had defined using wrappers. That gives us a systematic way to add logic depending on the output of run and any exceptions that might arise, such as logging the error and context, sending a chat notification, retrying under some circumstances, etc.

The following code

class MyImporter
  include WorkerTools::Basic
  wrappers :basics

  def run
    # do stuff
  end

  # ..
end

is internally handled as

def perform(model_id)
  # set model
  with_wrapper_basics do
    run
  end
end

where this wrapper method looks like

def with_wrapper_basics(&block)
  block.yield # calls run
  # marks the import as complete
  rescue Exception
  # marks the import as failed
  raise
end

if we also add a wrapper to send notifications, such as wrappers :basics, :rocketchat_error_notifier

the resulting nested calls would look like

def perform(model_id)
  # set model
  with_wrapper_basics do
    with_wrapper_rocketchat_error_notifier do
      run
    end
  end
end

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/i22-digitalagentur/worker_tools.

License

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