Terraform: Autoscaling Group Demo

Build out an autoscaling group for a microservice.

Inputs

Inputs are set in file terraform.tfvars. They are:

• S3 Bucket Name: must be unique
• Public Key (string): This is the key pair used to access instance and trigger auto-scaling

Outline

• The microservice code is available as a zip file: files/hit-counter-master.zip

• An S3 bucket is created and the code zip file is uploaded to it

• A new Autoscaling group is created consisting of:

  • A launch config based on a specified AMI (defaults to an AMI from us-west-2)
  • An Instance Role is applied for S3 Read-Only access
  • A new security group is created and applied to launch config
  • NodeJS, PM2 (process manager) and the microservice are installed and started via UserData
  • An autoscaling policy is setup to manage number of instances
  • A CloudWatch alarm tracking instance metrics is attached to autoscaling group

• A new ELB is created and instances are registered

Demo:

• Run terraform plan, follow instructions as needed.

  • terraform init is needed to initialize
  • View output of terraform plan to see what will be created

• Run terraform run to start provisioning resources

  • final output will be the Elastic Load Balancer URL
  • ELB url format: http://ms-elb-xxxxxxx.<region>.elb.amazonaws.com/)
  • Accessed via browser, outputs JSON : {"hits": NNN,"name":"hit-counter-pid-XXX","host":"ip-XXX-XXX-XXX-XXX"}

• Subscribe to SNS topic hit-counter-asg under AWS Console > SNS > Topics hit-counter-asg

  • Choose EMAIL or SMS as protocol and confirm subscription

• Find newly created instance under AWS Console > EC2 > Name ms_asg and lookup it's public IP

• Use the SSH Private Key (pair of public key specified earlier) to access instance

  • Access using ssh -i <private_key_file> ec2-user@<public ip>

• Using the stress tool, simulate high CPU Utilization and trigger the scaling up of instances.

stress --cpu 2

Terraform setup based on:

• Blog - https://aws.amazon.com/blogs/apn/terraform-beyond-the-basics-with-aws/

• Github - https://github.com/awslabs/apn-blog/tree/tf_blog_v1.0/terraform_demo

• Autoscaling Stack: https://github.com/unifio/terraform-aws-asg

Dependency graph generation (using GraphViz):

terraform graph -draw-cycles -type=plan > autoscaling_graph
"c:\Program Files (x86)\Graphviz2.38\bin\dot.exe" -Tpng autoscaling_graph > graph.png