Lamby Rails: A Rails+Lamby Example App

This app was created by following the official Lamby Quick Start Guide.

Notes

Generate the initial Rails app:

brew install awscli jq
brew tap aws/tap
brew install aws-sam-cli

asdf shell ruby 2.7.1

gem install rails -N

rails new lamby_rails \
  --skip-action-mailer --skip-action-mailbox --skip-action-text \
  --skip-active-record --skip-active-storage --skip-puma \
  --skip-action-cable --skip-spring --skip-listen --skip-turbolinks \
  --skip-system-test --skip-bootsnap

cd lamby_rails

git add .
git commit -m 'initial'

Edit app/controllers/application_controller.rb:

class ApplicationController < ActionController::Base
+  def index
+    render html: "<h1>Hello Lamby</h1>".html_safe
+  end
end

Edit config/routes.rb:

Rails.application.routes.draw do
+  root to: "application#index"
end

Save progress:
```
git add -p
git commit -m 'hello lamby'
```
Install lamby gems:
```
bundle add lamby aws-sdk-ssm
```

Edit Gemfile:

- gem "lamby", "~> 2.0"
+ gem "lamby", "~> 2.0", require: false

Finish installing lamby:

./bin/rake -r lamby lamby:install

git add -p
git status
git add .
git commit -m 'install lamby'

I set up my AWS credentials here:

# ~/.aws/credentials
[lamby_rails]
aws_access_key_id = VALUE
aws_secret_access_key = SECRET_VALUE

And the region config here:

# ~/.aws/config
[lamby_rails]
output = json
region = us-west-1

I set my AWS_PROFILE using direnv. Edit .envrc:
```
export AWS_PROFILE=lamby_rails
```
then run:
```
direnv allow
```

Configure SSM w/ Rails master key:

aws ssm put-parameter \
  --name "/config/lamby_rails/env/RAILS_MASTER_KEY" \
  --type "SecureString" \
  --value $(cat config/master.key)

Edit app.rb and add this line right after require 'lamby':

ENV['RAILS_MASTER_KEY'] =
  Lamby::SsmParameterStore.get!('/config/lamby_rails/env/RAILS_MASTER_KEY')

Edit template.yaml CloudFormation/SAM file by adding this to the Properties section of your RailsFunction. This addition allows your Lambda's runtime policy to read configs from SSM Parameter store (see full template.yml attached):

Policies:
  - Version: "2012-10-17"
    Statement:
      - Effect: Allow
        Action:
          - ssm:GetParameter
          - ssm:GetParameters
          - ssm:GetParametersByPath
          - ssm:GetParameterHistory
        Resource:
          - !Sub arn:aws:ssm:${AWS::Region}:${AWS::AccountId}:parameter/config/lamby_rails/*

Save progress:

git add -p
git commit -m 'configure lamby'

Edit .envrc (change the bucket name):

export CLOUDFORMATION_BUCKET=lamby-rails-josh
export AWS_DEFAULT_REGION=us-west-1

don't forget:

direnv allow

Now run:

aws s3 mb "s3://$CLOUDFORMATION_BUCKET"

./bin/deploy

This uses Docker to bake the Rails app Lambda function. That can take a long time on macOS. Go get some coffee or tea. :)
```
$ time ./bin/deploy

Successfully created/updated stack - lambyrails-production-us-west-1 in None
./bin/deploy  17.45s user 9.86s system 5% cpu 9:04.13 total
```
(that's the build/deploy time on an 8-core MacBook Pro 🤔)

joshuap/lamby_rails

Lamby Rails: A Rails+Lamby Example App

Links

Notes