Latchu@DevOps

Posted on Aug 29

Part-35: 🚀 Deploying an Unmanaged Instance Group with Load Balancer in Google Cloud Platform (GCP)

#googlecloud #devops #cloud #tutorial

When running workloads on Google Cloud Platform (GCP), managing VM instances in groups allows you to distribute traffic and increase reliability. While Managed Instance Groups (MIGs) are typically recommended, sometimes you may want to use Unmanaged Instance Groups (UMIGs) to manually control non-identical VMs.

In this tutorial, we’ll walk through creating an Unmanaged Instance Group, attaching a health check, creating a firewall rule, and finally exposing it through a Load Balancer.

🔹 What is an Unmanaged Instance Group?

Allows non-identical VMs in the same group (e.g., e2-micro + e2-small).
Supports load balancing.
❌ Does not support autoscaling, auto-healing, rolling updates, or multi-zone deployments.
No instance template required.
⚠️ Not recommended for production unless you specifically want to manage VMs yourself.

🛠️ Step-01: Setup & Introduction

We’ll create:

Two VM instances running Nginx.
An Unmanaged Instance Group.
A Health Check & Firewall Rule.
An HTTP Load Balancer.
Finally, verify traffic distribution across VMs.

First, ensure you have a webserver-install.sh file in your Cloud Shell:

#!/bin/bash
sudo apt install -y telnet
sudo apt install -y nginx
sudo systemctl enable nginx
sudo chmod -R 755 /var/www/html
HOSTNAME=$(hostname)
sudo echo "<!DOCTYPE html> <html> <body style='background-color:rgb(250, 210, 210);'>
<h1>Welcome to Latchu@DevOps - WebVM App1</h1>
<p><strong>VM Hostname:</strong> $HOSTNAME</p>
<p><strong>VM IP Address:</strong> $(hostname -I)</p>
<p><strong>Application Version:</strong> V1</p>
<p>Google Cloud Platform - Demos</p>
</body></html>" | sudo tee /var/www/html/index.html

🛠️ Step-02: Create VMs

# Set project
gcloud config set project gcpdemos

# VM1 - e2-micro
gcloud compute instances create vm1 \
  --zone=us-central1-a \
  --machine-type=e2-micro \
  --tags=http-server \
  --metadata-from-file=startup-script=webserver-install.sh 

# VM2 - e2-small
gcloud compute instances create vm2 \
  --zone=us-central1-a \
  --machine-type=e2-small \
  --tags=http-server \
  --metadata-from-file=startup-script=webserver-install.sh

Step-03: Create Unmanaged Instance Group

Goto > Compute Engine > Instance groups > Create a new Unmanaged Instance group

Name: umig-1
Description: unmanaged-instance-group-1
Location: us-central1(IOWA)
Zone: us-central1-a
Network: default (leave to defaults)
Subnetwork: default (leave to defaults)
VM Instances: vm1, vm2
Specify Port Name Mapping:

Port Name: webserver-port
Port Numbers: 80

Click on CREATE

CLI

# Create UMIG
gcloud compute instance-groups unmanaged create umig-1 \
   --zone=us-central1-a \
   --description=unmanaged-instance-group-1

# Add named port for HTTP
gcloud compute instance-groups unmanaged set-named-ports umig-1 \
   --zone=us-central1-a \
   --named-ports=webserver-port:80

# Add VMs to UMIG
gcloud compute instance-groups unmanaged add-instances umig-1 \
   --zone=us-central1-a \
   --instances=vm1,vm2

Step-04: Review Unmanaged Instance Group Properties

Go to Compute Engine -> Instance Groups -> Click on umig-1
Review the following Tabs

Overview
Details
Monitoring
Errors (Not applicable for Unmanaged Instance Groups)

Step-05: Create Health Check

What is Health Check?

A health check determines whether a VM instance is healthy by sending requests to the instance.
An instance is considered healthy if it returns consecutive responses within a specified time.
Health checks are used for load balancing and autoscaling managed instance groups

Go to Compute Engine -> Instance Groups -> Health Checks -> CREATE HEALTH CHECK
Name: app1-health-check
Description:
Scope: Regional
Region: us-central-1 (IOWA)
Protocol: HTTP
Port: 80
Proxy Protocol: None
Request Path: /index.html
Response: Welcome
Host HTTP Header: leave empty (leave to defaults)
Logs: Off (leave to defaults) If enabled Cloud Logging cost is going to be high
Health Criteria: Leave to defaults

CLI

# Create Health Check
gcloud compute health-checks create http app1-health-check \
   --project=gcpdemos \
   --port=80 \
   --request-path=/index.html \
   --proxy-header=NONE \
   --response=Welcome \
   --region=us-central1 \
   --no-enable-logging \
   --check-interval=10 \
   --timeout=5 \
   --unhealthy-threshold=3 \
   --healthy-threshold=2

Click on Create

Step-06: Create a firewall rule to allow health check probes to connect to your app

Health check probes come from addresses in the ranges 130.211.0.0/22 and 35.191.0.0/16, so make sure your firewall rules allow the health check to connect.

# Create Firewall rule
gcloud compute firewall-rules create allow-health-check \
    --allow tcp:80 \
    --source-ranges 130.211.0.0/22,35.191.0.0/16 \
    --network default

Goto > Networks > default

Step-07: Create a Load Balancer

Go to Network Services -> Load Balancing -> Create Load Balancer -> HTTP(S) Load Balancing -> START CONFIGURATION
Internet facing or internal only: From internet to my VMs
Single Region deployment
Create Loadbalancer and Configure
Click on Continue
Name: lb-for-umig1
WARNING: Click on RESERVE SUBNET

NAME: proxy-only-subnet
IP Address: 10.0.0.0/24
Click on CREATE

Frontend Configuration

New Frontend IP and port
Name: fip-lb-umig
Protocol: HTTP
Network Service Tier: Premium
IP Version: IPV4
IP Address: Click on CREATE IP ADDRESS

NAME: sip-lb-umig
DESCRIPTION: sip-lb-umig

Port: 80
Click on DONE

CREATE A BACKEND SERVICE

Click on CREATE A BACKEND SERVICE
Name: lb-backend-umig
Description: lb-backend-umig
Backend Type: Instance Group
Protocol: HTTP
Naed Port: http
Timeout: 30
New backend: umig-1

Port Numbers: 80 (select webserver-port named port from that instance group)
Balancing mode: Utilization
Maximum backend utilization: 80
Maximum RPS: leave empty (leave to defaults)
Scope: per instance (leave to defaults)
Capacity: 100
Click on DONE
Click on CREATE
Cloud CDN: leave it unchecked (leave to defaults)
Health check: app1-health-check
Logging: leave unchecked (leave to defaults)
Security: leave unselected (leave to defaults)
Click on CREATE

Host and Path Rules

Mode: Simple host and path rule

Review and Finalize

Front End
Backend

Click on CREATE
It will take 3 to 5 minutes to create the load balancer.

Step-08: Verify Load Balancer Properties after creation

Go to Network Services -> Load Balancing -> lb-for-umig
Verify if Instances are Healthy

Step-09: Access Sample Application using LB IP

# Access Sample App
http:/;<LB-IP-ADDRESS>
http://35.209.128.93
Observation: 
1. Keep refreshing to see the output from both Virtual Machines
2. You will see output from both VMs switching

# Curl with while loop runs every 1 second
while true; do curl http://35.209.128.93/; sleep 1; done

Step-10: Clean-Up - Delete Load Balancer

Go to Network Services -> Load Balancing -> lb-for-unmanaged-instance-group
Click on DELETE
Select Backend services:lb-backend-umig for deletion
Leave Health Checks: app1-health-check unchecked to not to delete
Click on DELETE LOAD BALANCER AND SELECTED RESOURCES

Step-11: Clean-Up Delete Unmanaged Instance Group

Go to Compute Engine -> Instance Groups -> Click unmanaged-instance-group-1
Click on DELETE GROUP

# Delete Instance Group - Unmanaged
gcloud compute instance-groups unmanaged delete unmanaged-instance-group-1 \
   --project=gcpdemos \
   --zone=us-central1-a

Step-12: Clean-Up - Delete VM Instances

Delete the VM instances

# Delete VM 
gcloud compute instances delete vm1 --zone=us-central1-a
gcloud compute instances delete vm2 --zone=us-central1-a

# List VMs
gcloud compute instances list --filter='name:vm1'
gcloud compute instances list --filter='name:vm2'

Step-13: Clean-Up - Release External IP Address used for LB

Go to VPC Networks -> External IP Addresses
Select sip-lb-umig and click on RELEASE STATIC IP ADDRESS

# Delete External Static IP Address
gcloud compute addresses delete sip-lb-umig \
   --project=gcpdemos \
   --region=us-central1

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