Create a HTTP load balancer in GCP

lb-backend.sh

# Set default region and zone
gcloud config set compute/region europe-west1
gcloud config set compute/zone europe-west1-b

# Create an instance template
gcloud compute instance-templates create lb-backend-template \
   --region=europe-west1 \
   --network=default \
   --subnet=default \
   --tags=allow-health-check \
   --machine-type=e2-medium \
   --image-family=debian-12 \
   --image-project=debian-cloud \
   --metadata=startup-script='#!/bin/bash
     apt-get update
     apt-get install apache2 -y
     a2ensite default-ssl
     a2enmod ssl
     vm_hostname="$(curl -H "Metadata-Flavor:Google" \
     http://metadata.google.internal/computeMetadata/v1/instance/name)"
     echo "Page served from: $vm_hostname" | \
     tee /var/www/html/index.html
     systemctl restart apache2'

# Create a managed instance group
gcloud compute instance-groups managed create lb-backend-group \
   --template=lb-backend-template --size=2 --zone=europe-west1-b

# Create a firewall rule to allow health checks
gcloud compute firewall-rules create fw-allow-health-check \
  --network=default \
  --action=allow \
  --direction=ingress \
  --source-ranges=130.211.0.0/22,35.191.0.0/16 \
  --target-tags=allow-health-check \
  --rules=tcp:80

# Create a global static IP address
gcloud compute addresses create lb-ipv4-1 \
  --ip-version=IPV4 \
  --global

# Create a health check
gcloud compute health-checks create http http-basic-check \
  --port 80

# Create a backend service and add the instance group
gcloud compute backend-services create web-backend-service \
  --protocol=HTTP \
  --port-name=http \
  --health-checks=http-basic-check \
  --global

# Add the instance group to the backend service
gcloud compute backend-services add-backend web-backend-service \
  --instance-group=lb-backend-group \
  --instance-group-zone=europe-west1-b \
  --global

# Create a URL map to route requests to the backend service
gcloud compute url-maps create web-map-http \
    --default-service web-backend-service

# Create an HTTP proxy to route requests
gcloud compute target-http-proxies create http-lb-proxy \
    --url-map web-map-http

# Create a global forwarding rule to route incoming requests to the proxy
gcloud compute forwarding-rules create http-content-rule \
   --address=lb-ipv4-1\
   --global \
   --target-http-proxy=http-lb-proxy \
   --ports=80

You need to create resources for the HTTP load balancer. You can read more about Managed instance groups (MIGs).

Set the values as follows, leaving all others at their defaults:

Property	Value (type value or select option as specified)
Backend Template	lb-backend-template
tags	allow-health-check
Managed instance group	lb-backend-group
machine-type	e2-medium
image-family and image-project	same as previously created VMs
fw-allow-health-check	fw-allow-health-check
Allow source-ranges	130.211.0.0/22, 35.191.0.0/16
Traffic	ingress
Port	80
external IP address	lb-ipv4-1
health check	http-basic-check
URL map	web-map-http
Target http proxy	http-lb-proxy