Install gem in Serverless Framework and AWS Lambda with Ruby environment

How to deploy AWS Lambda Ruby script that requires gem installation with Serverless Framework.

Procedure outline

You can easily do it by inserting a plugin.

1. serverless plugin install -n serverless-ruby-layer
2. Create Gemfile
3. After that, if you deploy normally, it will do various things without permission

Detailed procedure

Serverless Framework service creation

$ serverless create --template aws-ruby
Serverless: Generating boilerplate...
 _______                             __
|   _   .-----.----.--.--.-----.----|  .-----.-----.-----.
|   |___|  -__|   _|  |  |  -__|   _|  |  -__|__ --|__ --|
|____   |_____|__|  \___/|_____|__| |__|_____|_____|_____|
|   |   |             The Serverless Application Framework
|       |                           serverless.com, v2.16.1
 -------'

Serverless: Successfully generated boilerplate for template: "aws-ruby"
Serverless: NOTE: Please update the "service" property in serverless.yml with your service name

Three files will be generated.

.gitignore
handler.rb
serverless.yml

Plugin installation

Install a plugin called serverless-ruby-layer.

$ serverless plugin install -n serverless-ruby-layer

The following files and directories will increase.

node_modules
package.json
package-lock.json

Since Serverless Framework is implemented in Node.js, it seems that node_modules and package.json exist even though it is a Ruby project.

Source code

serverless.yml

serverless.yml has the following contents. The description of plugins is added without permission when the plugin is installed.

service: sample

frameworkVersion: '2'

provider:
  name: aws
  runtime: ruby2.7
  region: ap-northeast-1

functions:
  hello:
    handler: handler.hello

plugins:
  - serverless-ruby-layer

Gemfile

Create a Gemfile with the following contents.

Let's use holiday_japan as a sample of gem. A gem that determines Japanese holidays.

source "https://rubygems.org"

gem 'holiday_japan'

Ruby source code

handler.rb

require 'json'
require 'holiday_japan'

def hello(event:, context:)
  holidayName = HolidayJapan.name(Date.new(2021, 8, 8))
  puts(holidayName) #To CloudWatch"Mountain day"Is written out
end

Deploy

If you create it so far and then deploy it with the serverless command, not only the Lambda itself but also the serverless command will automatically create a gem-installed image and upload it as a layer of AWS Lambda.

$ serverless deploy -v

Run

Looking at the deployment results in the AWS Management Console, it looks like this:

Lambda

Layer

Execution result CloudWatch Logs

Link

-(Python version) Pip installation in Serverless Framework and AWS Lambda with Python environment