Serverless use cases for Web projects

Oleksii Vasyliev

• Web and Mobile Developer, DevOps
• Open-Source libs: Certonid, Storybook Addon Root Attribute, PGTune, SQL Joins Visualizer, etc
• Open-Source books: Setting up and scaling of PostgreSQL (Russian), Cooking Infrastructure by Chef
• Leading RWpod podcast about Ruby and JavaScript

Serverless

Serverless Solutions

Ruby on Serverless

Resize Images on S3 bucket

AWS S3 events

  # Gemfile
  source 'https://rubygems.org'

  gem 'aws-sdk-s3'
  gem 'mini_magick'

# handler.rb
require 'resizer'

class ImageHandler

  def self.process(event:, context:)
    event = event["Records"].first
    bucket_name = event["s3"]["bucket"]["name"]
    object_name = event["s3"]["object"]["key"]

    file = Resizer.from_s3(bucket_name, object_name)
    file.resize "100x100"
    file.upload_file("resized-your-images", "resized_" + event["s3"]["object"]["key"] )
  end
end

require "aws-sdk-s3"
require "mini_magick"

class Resizer
    def resize(params)
        image = MiniMagick::Image.open(@tmp_file)
        ...
        image.write @resized_tmp_file
    end

    def upload_file(target_bucket, target_object)
        s3 = Aws::S3::Resource.new()
        object = s3.bucket(target_bucket).object(target_object).upload_file(@resized_tmp_file)
    end
end

AWS API Gateway

AWS API Gateway

http://YOUR_CLOUDFRONT_WEBSITE_HOSTNAME_HERE/300×300/your_image.jpg

http://YOUR_CLOUDFRONT_WEBSITE_HOSTNAME_HERE/25×25/your_image.jpg

http://YOUR_CLOUDFRONT_WEBSITE_HOSTNAME_HERE/500×500/your_image.jpg

AWS Lambda@Edge

Use case with static website

CloudFront does allow you to specify a default root object (index.html), but it only works on the root of the website (such as http://www.example.com > http://www.example.com/index.html). It does not work on any subdirectory (such as http://www.example.com/about/)

https://railsware.com/ - works on CloudFront

https://railsware.com/railswarians/ - not resolve to "index.html"

exports.handler = (event, context, callback) => {
  const request = event.Records[0].cf.request;

  if (request.uri.match('.+/$')) {
    request.uri += 'index.html';
    callback(null, request);
  } else if (request.uri.match('(.+)/index.html')) {
    ...
  }
}

  ...
  } else if (request.uri.match('(.+)/index.html')) {
    const prefixPath = request.uri.match('(.+)/index.html');
    const response = {
      status: '301',
      statusDescription: 'Found',
      headers: {
        location: [{
          key: 'Location', value: prefixPath[1] + '/',
        }],
      }
    };
    callback(null, response);
  } else if (request.uri.match('/[^/.]+$')) {
    ...
  }
}

  ...
  } else if (request.uri.match('/[^/.]+$')) {
    const response = {
      status: '301',
      statusDescription: 'Found',
      headers: {
        location: [{
          key: 'Location', value: request.uri + '/',
        }],
      }
    };
    callback(null, response);
  } else {
    callback(null, request);
  }
}

Lambda@Edge Use Cases

• Website Security and Privacy (add headers for response)
• Search Engine Optimization (SEO)
• Intelligently Route Across Origins and Data Centers
• Bot Mitigation at the Edge
• Real-time Image Transformation
• A/B Testing
• User Authentication and Authorization
• User Tracking and Analytics

AWS Lambda + AWS Route53 + AWS S3 = Letsencrypt wildcard certificate

• github.com/railsware/acme-aws-lambda
• github.com/railsware/s3_fetch_certs

load_paths = Dir["./vendor/bundle/ruby/2.5.0/bundler/gems/**/lib"]
$LOAD_PATH.unshift(*load_paths)
require 'acme_aws_lambda'

AcmeAwsLambda.configure do |config|
  config.production_mode = true
  config.contact_email = 'admin@example.com'
  config.domains = ['example.com', '*.example.com']
  config.common_name = '*.example.com'
  config.s3_bucket = 'example.com-certificates'
  config.s3_certificates_key = 'certificates/example.com'
  config.route53_domain = 'example.com'
end

def handler(event:, context:)
  AcmeAwsLambda.create_or_renew_cert
end

Cron task to update certificates

 # crontab
0 3 * * * /opt/s3_fetch/s3_fetch_certs
-accessKeyId="access-key"
-secretAccessKey="secret-access-key"
-bucket="s3-bucket" -certsKey="path-on-s3"
-outDirectory="/etc/nginx/certs" -outName="production"
-runAfterChange="systemctl reload nginx"

$ certonid -h

Usage:
  certonid [OPTIONS] COMMAND [ARG...]
  certonid [command]

Available Commands:
  completion  Generates bash completion scripts
  decrfile    Decrypt file
  decrstr     Decrypt text
  encrfile    Encrypt file
  encrstr     Encrypt text
  gencert     Generate user or host certificate
  help        Help about any command
  randstr     Generate random string (32 bytes)

Pros

• Pricing (free tier)
• Reduced maintenance
• Scalability
• Faster delivery
• Security

Cons

• Vendor-operated environment
• Limits and cost alterations
• Security
• Cold starts
• Not efficient for long-running applications
• Performance (functions with less RAM have slower CPU speed)
• Test functions locally sometimes improssible

Serverless Cost

• Cost-calculator.bref.sh - Serverless costs calculator
• Serverlesscalc.com - Serverless Cost Calculator
• Servers.lol - Should your EC2 be a Lambda?

Tips

• Lambda functions are completely isolated from the public Internet
• Executing a Lambda from another Lambda is slow
• Optimize for your language
• Deploy fault-tolerant code (idempotence). Your Lambda function might execute twice
• Use Dead Letter Queues to save event invocation data
• Use metrics for better observability

<Thank You!> Questions?