Ruby on Jets - AWS serverless framework for Ruby on Rails

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Ruby on Rails (RoR) is my favorite web framework, and today I will share an AWS serverless framework of RoR: Ruby on Jets. I’m not an AWS expert and even have no AWS certifications, and besides, this is my first time to use AWS Lambda, API gateway, dynamodb, and other serverless services.

Preparation:#

  1. Add aws_access_key_id and aws_secret_access_key to ~/.aws/credentials
  2. Docker / Docker-compose I use in this demo.

Let’s look at initial project structure:
project-structure.png

There’s my Gemfile, Dockerfile, and docker-compose.yml

Gemfile

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source "https://rubygems.org"

gem "jets", "~> 3.0.0"

Dockerfile

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FROM ruby:2.7
RUN apt-get update \
    && apt-get -y install rsync zip

WORKDIR /api
COPY ./api /api
RUN bundle install

docker-compose.yml

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version: '3'

services:
  api:
    build:
      context: ../
      dockerfile: docker/api/Dockerfile
    command: bash -c "bundle exec jets server --port 3000 --host 0.0.0.0"
    environment:
      - AWS_PROFILE=default
      - AWS_REGION=ap-northeast-2
    volumes:
      - '../api:/api'
      - ~/.aws:/root/.aws
    ports:
      - "3000:3000"
    depends_on:
      - dynamodb
      - db
  dynamodb:
    image: instructure/dynamo-local-admin
    ports:
      - "8000:8000"
      - "8001:8001"
      - "8002:8002"
  db:
    image: mysql:8
    environment:
      MYSQL_ROOT_PASSWORD: root
      MYSQL_DATABASE: app
      MYSQL_USER: docker
      MYSQL_PASSWORD: docker
      TZ: 'Asia/Taipei'
    ports:
      - 3306:3306
    volumes:
      - ./mysql/conf.d:/etc/mysql/conf.d

Then, We go to docker folder to run docker-compose run api jets new . --database=mysql to install gems and generate Jets project.
jets-new.png

Now we can use docker-compose up --build to build api, db, and dynamodb containers.
docker-build.png

Can you see it? >> localhost:3000
localhost.png

Let’s CRUD#

We have to grant DB user first:

In docker folder

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$ > docker-compose exec db /bin/bash

In db container

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root@db0c0d54dfef:/# mysql -uroot -p
mysql> GRANT ALL ON *.* to docker@'%';

After granting docker permission, we can generate scaffold, create database and install webpacker by using jets:

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docker-compose exec api jets generate scaffold post title:string
docker-compose exec api jets db:create db:migrate
docker-compose exec api jets webpacker:install

Go to localhost/posts and see the result:
localhost-posts

Finally, we are ready to deploy. env-file shows how to set environments. Let’s go to AWS RDS create a MySQL RDS, and set value to .env.development.remote.
development-remote

Well done! Deploy it.

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docker-compose exec api sh -c 'JETS_ENV_REMOTE=1 bundle exec jets db:create db:migrate'
docker-compose exec api sh -c 'JETS_ENV_REMOTE=1 bundle exec jets deploy'

jets-deploy

…….Waiting……

We will get a URL, and we can get the page by clicking URL
jets-deploy-done

serverless-page

That’s all. But I have to mention that if you get ERROR: Limit Reached when you deploy, you need to check serverlessgems rate-limits page. That’s why we eventually used AWS CDK and changed the language to Typescript in our Firstage All-in-one blog.

Next time I will introduce AWS CDK and which services we use.