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Terraform: Autoscaling Group Demo

Build out an autoscaling group for a microservice.


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


  • The microservice code is available as a zip file: files/

  • 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


  • 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>
    • 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:

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


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