Rails中配置邮件定时发送：注册时及注册3个月后发件

Hey Mike, great question! Let's break this down into manageable steps to get that scheduled email up and running without disrupting your existing signup flow. I'll cover two common approaches for Rails scheduled tasks — pick the one that fits your setup best.

First: Prep the Email Template & Mailer Method #

Since you already have signup emails working with the exchange gem, we just need to add a new email for the 3-month follow-up:

1. Open your user mailer (probably app/mailers/user_mailer.rb) and add a new method:

   class UserMailer < ApplicationMailer
     # Your existing signup email method here
     def welcome_email(user)
       # ... your existing code
     end
   
     # New 3-month follow-up email
     def three_months_after_signup_email(user)
       @user = user
       mail(to: @user.email, subject: "We Missed You! Three Months Since You Joined")
     end
   end
   

2. Create the email templates in app/views/user_mailer/:

   • three_months_after_signup_email.html.erb (HTML version)
   • three_months_after_signup_email.text.erb (plain text fallback)
     Fill these with your desired follow-up content — keep it personal!

Option 1: Use the whenever Gem (Simple Cron Jobs) #

If you don't have a background queue set up, whenever is a straightforward way to manage cron tasks through Ruby.

Steps: #

1. Add the gem to your Gemfile:

   gem 'whenever', require: false
   

   Run bundle install to install it.

2. Generate the schedule config file:

   wheneverize .
   

   This creates config/schedule.rb.

3. Configure the daily cron job in config/schedule.rb:

   every :day, at: '2:00 am' do # Run daily at 2 AM (low traffic time)
     runner "User.send_three_month_followup_emails"
   end
   

4. Add the method to your User model to handle finding users and sending emails:

   class User < ApplicationRecord
     # Add a column to track if we've sent this email (prevents duplicates!)
     # Run this migration first: rails generate migration AddThreeMonthsEmailSentAtToUsers three_months_email_sent_at:datetime
     # Then run rails db:migrate
   
     def self.send_three_month_followup_emails
       # Find users who signed up exactly 3 months ago and haven't gotten the email yet
       three_months_ago_window = 3.months.ago.beginning_of_day..3.months.ago.end_of_day
       eligible_users = where(created_at: three_months_ago_window, three_months_email_sent_at: nil)
   
       eligible_users.each do |user|
         UserMailer.three_months_after_signup_email(user).deliver_now
         user.update!(three_months_email_sent_at: Time.current)
       end
     end
   

5. Deploy the cron job:

   # For production
   whenever --update-crontab
   # For development (if you want to test locally)
   whenever --update-crontab --set environment=development
   

Option 2: Use Sidekiq + Sidekiq-Cron (Background Queue, Recommended) #

If you're already using Sidekiq for background jobs, this is the better approach — it keeps email sending off your main server and is more scalable.

Steps: #

1. Add the gems to your Gemfile:

   gem 'sidekiq'
   gem 'sidekiq-cron'
   

   Run bundle install.

2. Configure Sidekiq to load cron jobs on startup. Create/modify config/initializers/sidekiq.rb:

   Sidekiq.configure_server do |config|
     config.on(:startup) do
       # Load cron jobs from the schedule.yml file
       Sidekiq::Cron::Job.load_from_hash YAML.load_file(Rails.root.join('config', 'schedule.yml'))
     end
   end
   
   Sidekiq.configure_client do |config|
     # Standard Sidekiq client config (if you already have this, leave it)
   end
   

3. Create the cron schedule file config/schedule.yml:

   send_three_month_followup_emails:
     cron: "0 2 * * *" # Daily at 2 AM (cron syntax: minute hour day month weekday)
     class: "ThreeMonthsAfterSignupWorker"
     queue: default
   

4. Create the Sidekiq worker in app/workers/three_months_after_signup_worker.rb:

   class ThreeMonthsAfterSignupWorker
     include Sidekiq::Worker
     sidekiq_options retry: 3 # Retry failed emails 3 times
   
     def perform
       three_months_ago_window = 3.months.ago.beginning_of_day..3.months.ago.end_of_day
       # Use find_each to handle large user lists efficiently
       User.where(created_at: three_months_ago_window, three_months_email_sent_at: nil).find_each do |user|
         UserMailer.three_months_after_signup_email(user).deliver_later
         user.update!(three_months_email_sent_at: Time.current)
       end
     end
   end
   

5. Start Sidekiq (and make sure it runs in production):

   bundle exec sidekiq
   

   For deployment, use a process manager like systemd or supervisord to keep Sidekiq running.

Key Notes to Avoid Headaches #

• Prevent duplicate emails: The three_months_email_sent_at column is critical — don't skip adding that migration. It ensures you never send the same email twice to a user.
• Test locally: For development, you can tweak the cron schedule to run every minute (* * * * *) to test quickly, or manually trigger the worker/method in the Rails console:

  # For whenever approach
  User.send_three_month_followup_emails
  # For Sidekiq approach
  ThreeMonthsAfterSignupWorker.perform_async
  

• Use deliver_later: If using Sidekiq, always use deliver_later instead of deliver_now to offload email sending to the background.

Let me know if you hit any snags — whether it's setting up the migration, tweaking the cron schedule, or troubleshooting email delivery!

内容的提问来源于stack exchange，提问作者Mike