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Usage

Initial Setup

Add patches to the project Gemfile

gem 'patches', '~> 2.4.0'

Install the database migration

bundle exec rake patches:install:migrations

Migrate database

bundle exec rake db:migrate

Configuration

If you would like to run the patches asynchronously, or would like them to notify your Slack channel when they fail or succeed, you need to set up an initializer to set those options.

Patches::Config.configure do |config|
  config.use_sidekiq = true

  config.use_slack = true
  config.slack_options = {
    webhook_url: ENV['SLACK_WEBHOOK_URL'],
    channel: ENV['SLACK_CHANNEL'],
    username: ENV['SLACK_USER']
  }
end

Additionally, you can override the default prefix and suffix of the notification message in the patches config:

  # for example
  config.notification_prefix = "#{Tenant.current.name}-#{Rails.env}"  # => [READYTECH-STAGING]
  config.notification_suffix = Tenant.current.name  # => ... patches succeeded for Readytech

Running patches in parallel for tenants

If you are using the Apartment gem, you can run the patches for each tenant in parallel. Just set the config sidekiq_parallel to true and you're good to go.

Patches::Config.configure do |config|
  config.use_sidekiq = true
  config.sidekiq_parallel = true
end

Note: Make sure your sidekiq queue is able to process concurrent jobs. You can use config.sidekiq_options to customise it.

Application version verification

In environments where a rolling update of sidekiq workers is performed during the deployment, multiple versions of the application run at the same time. If a Patches job is scheduled by the new application version during the rolling update, there is a possibility that it can be executed by the old application version, which will not have all the required patch files.

To prevent this case, set the application version in the config:

Patches::Config.configure do |config|
  revision_file_path = Rails.root.join('REVISION')

  if File.exist?(revision_file_path)
    config.application_version = File.read(revision_file_path)
    config.retry_after_version_mismatch_in = 1.minute
  end
end

Creating Patches

Generate a patch

bundle exec rails g patches:patch PreferenceUpdate

Which will result in a file like below

class PreferenceUpdate < Patches::Base
  def run
    # Code goes here
  end
end

update the run method and then execute

Generate patch with specs

bundle exec rails g patches:patch PreferenceUpdate --specs=true
bundle exec rake patches:run

Patches will only ever run once, patches will run in order of creation date.

To run patches on deployment using Capistrano, edit your Capfile and add

require 'patches/capistrano'

And then in your deploy.rb

after 'last_task_you_want_to_run' 'patches:run'

If you are using sidekiq and restarting the sidekiq process on the box as a part of the deploy process, please make sure that the patches run task runs after sidekiq restarts, otherwise there is no guarentee the tasks will run.

File Download

If a patch requires data assets, you could use S3 to store the file. If credentials are defined in env vars, as per https://docs.aws.amazon.com/cli/latest/topic/config-vars.html#id1

require 'aws-sdk-s3'
Aws::S3::Client.new.get_object(bucket: @bucket_name, key: filename, response_target: destination)

Multitenant

Patches will detect if Apartment gem is installed and if there are any tenants and run the patches for each tenant