Kamal Rails Series Part 4: Configure Redis and Sidekiq

Next up in our Rails Kamal series is adding Redis and Sidekiq configuration. Sidekiq is a very well-known background task manager in the Rails community. Sidekiq uses Redis as a data store for scheduling jobs. In this article, we are going to build upon our existing configuration to add Redis and Sidekiq to our deployment.

Step 1: Add Redis to your Gemfile

# Gemfile

# Use Redis adapter to run Action Cable in production
gem "redis", "~> 4.0"

Step 2: Add Sidekiq (Skip if you already have Sidekiq jobs)

We will add Sidekiq to our Gemfile by doing bundle add sidekiq.

We will then create a dummy job by doing:

rails generate sidekiq:job dummy

Step 3: Add configuration in deploy.yml

#config/deploy.yml

# Name of your application. Used to uniquely configure containers.
service: rubypodcatcher

# Name of the container image.
image: joshio1/rubypodcatcher

# Deploy to these servers.
servers:
  web:
    hosts:
      - <SERVER_IP>
    options:
      network: "private"

  ..other configuration..
  
job:
    hosts:
      - <SERVER_IP>
    cmd: bundle exec sidekiq -q default -q mailers
    options:
      network: "private"

env:
  clear:
    HOSTNAME: rubypodcatcher.com
    DB_HOST: <SERVER_IP>
    RAILS_SERVE_STATIC_FILES: true
    RAILS_LOG_TO_STDOUT: true
    REDIS_URL: "redis://rubypodcatcher-redis:6379/0"
  secret:
    - RAILS_MASTER_KEY

accessories:
  redis:
    image: redis:latest
    host: <SERVER_IP>
    directories:
      - data:/data
    options:
      network: "private"

• If we don’t already have a private network created on the remote server, we need to create it as shown in a previous article in this series.

docker network create -d bridge private

• Note that if you have any other configuration in the deploy.yml file related to Postgres or any other configuration, that does not have to be modified.

Step 4: Add Redis as an accessory

Note that we have added Redis as an accessory. In order to deploy redis, we will use this command:

kamal env push
kamal accessory boot redis

Step 5: Deploy

Next step is to deploy on our remote server. We will do:

kamal deploy

How to check whether it’s working?

• To check whether redis is working fine:

irb(main):008:0> redis = Redis.new
=> #<Redis client v4.8.1 for redis://rubypodcatcher-redis:6379/0>
irb(main):009:0> 
irb(main):010:0> redis.set("sample_key", "sample_value")
=> "OK"

• To check whether Sidekiq is working fine:

irb(main):005:0> DummyJob.perform_async
2024-01-18T15:39:15.194Z pid=7 tid=2jb INFO: Sidekiq 7.2.0 connecting to Redis with options {:size=>10, :pool_name=>"internal", :url=>"redis://rubypodcatcher-redis:6379/0"}
=> "2ab8740502724b5d107182cd"

Conclusion:

• This article shows how we can deploy Sidekiq and Redis using Kamal on a Rails application. Rails 8 is going to use SolidQueue going forward which is a new technology that uses database as a data store instead of Redis. I’ll soon write about Solid Queue and Kamal.
• Check out these previous articles from this series:

Part 1: Deploying a basic Rails application using Kamal on Hetzner

• Part 2: Add Postgres to deployed Rails application using Kamal
• Part 3: Add SSL configuration using Kamal

Listen to this podcast where DHH talks about Rails and Kamal.

If you would like to search for specific terms or concepts or names in Ruby/Rails podcasts, check out rubypodcatcher.com