Azure VMSS Lifecycle Hook

This feature enables users to conduct a graceful shutdown on VMSS instance, when it is targeted for deletion. This provides huge flexibility for exceptional case handling on customer code.

Overall Architecture

Prerequisite

The subscription must opt in for this feature.
EnablePendingDeletion=true tag configured on the VMSS.

Overall Procedure

Core components

Web Service - healthprobe_flask

Delete VMSS Instance - delete_vmss_instance

Deployment

Environment

Overall evnironment will be deployed from terraform with following characteristics.

Availability Zone: not considered.
PublicLB: deployed with a NAT rule for ssh.
MSI: Enabled and configured as contributor on resource group.
Custom Extension: read bootstrap file.
VMSS scale-in policy: NewestVM, configured from the portal.
Application Gateway: Backend pool and custom probe configured for this VMSS.
Applictions: Written in python, leverages Azure REST API and Azure SDK for python.
Managed Image: Managed Image, which has data disk will be referred.
VMID : Numeric id of VMSS instance is parsed from "name" of IMDS from each VMSS instance.
Data Drive formatting : setup.sh has the code for fdisk and making an entry in /etc/fstab.
Managed Image : a managed image will be retrieved for provisioning of VMSS instance.
Versioning : This code supersedes https://github.com/bedro96/terraform_vmss_ag

Terraform

Clone this git and modify terraform.tfvars as required. Execute following commands to deploy the environment.

terraform init
terraform plan -out=vmss_ag.out
terraform apply vmss_ag.out

n-y-kim / terraform_vmss_from_image_with_multi_ag