Hacking Rails mail delivery for an async solution with Sidekiq, Redis, Local Postfix SMTP server

app mailers queue_deliver_mailer.rb

class QueueDeliveryMailer < ActionMailer::Base
  self.delivery_method = Rails.application.config.mail_queue_outbound_delivery_method #remember this from development.rb
  layout nil

  def rebuild_mail(id)
    mail({:from => $redis.get("mail:#{id}:sender_address"),
         :to => $redis.get("mail:#{id}:recipient_address"),
         :reply_to => $redis.get("mail:#{id}:reply_to_address"),
         :mime_version => $redis.get("mail:#{id}:mime_version"),
         :content_type => $redis.get("mail:#{id}:content_type"),
         :content_transfer_encoding => $redis.get("mail:#{id}:content_transfer_encoding"),
         :subject => $redis.get("mail:#{id}:subject")
         }) do |format|
      format.text {render :text => $redis.get("mail:#{id}:body")}
    end
  end
end

app workers mail_worker.rb

class MailWorker
  include Sidekiq::Worker

  def perform(id)
    m = QueueDeliveryMailer.rebuild_mail(id) #this is in mailers/queue_deliver_mailer.rb
    puts m.delivery_method
    puts m.delivery_method.settings
    puts m.deliver
  end
end

config environments development.rb

config.mail_queue_outbound_delivery_method = :smtp #to be used in a later mailer class used by Sidekiq worker

config initializers setup_mail.rb

ActionMailer::Base.add_delivery_method :queued, MailDebug::QueuedDelivery #now all mail is routed through this
ActionMailer::Base.delivery_method = :queued
ActionMailer::Base.raise_delivery_errors = true
ActionMailer::Base.perform_deliveries = true
ActionMailer::Base.smtp_settings = {
    address:              '127.0.0.1',
    port:                  25,
    domain:               'app.com',
}

config sidekiq.yml

verbose: true
:concurrency:  25
:queues:
  - [mailer, 5]
  - [default, 5]

lib mail_debug queued_delivery.rb

module MailDebug
  class QueuedDelivery
    def initialize(values={})
      #nothing
    end
    def deliver!(mail)
     
      queue_id = Time.now.to_s + ($redis.incr "next.mail_worker.id").to_s
      #Object schema mail:id:mail_field

      #push all mail headers in redis queue
      $redis.set "mail:#{queue_id}:mime_version", mail.mime_version
      $redis.set "mail:#{queue_id}:content_type", mail.content_type
      $redis.set "mail:#{queue_id}:content_transfer_encoding", mail.content_transfer_encoding
      $redis.set "mail:#{queue_id}:subject", mail.subject
      $redis.set "mail:#{queue_id}:body", mail.body
      $redis.set "mail:#{queue_id}:recipient_address", mail.to.first
      $redis.set "mail:#{queue_id}:sender_address", mail.from.first
      $redis.set "mail:#{queue_id}:reply_to_address", mail.reply_to ? mail.reply_to.first : nil

      MailWorker.perform_async(queue_id) #this is the sidekiq worker
    end
  end
end