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Internal HTTP Load Balancer Terraform Example

This example shows how to deploy an internal HTTP load balancer using plain terraform (i.e. without using any external modules). This example will create all the required resources needed for a working internal load balancer except the GCP project.

Design

In this example we use simple application (an nginx serving a simple HTML file) configured using a startup script. This application is deployed using a Managed Instance Group with a minimum of two instances.

Besides the computing resources, the code also deploys a VPC, the required subnets, and all the components elements of a load balancer (forwarding rule, URL map, health check, etc).

For testing purposes, an additional VM is also created. You can use this VM to confirm the load balancer is correctly configured.

Prerequisites

  1. You must have a recent version of Terraform installed (0.14+).
  2. A working GCP project with the GCE API enabled.

Deploy

The terraform code defines multiple variables. Most of the variables provide default values that can be safely used but you must provide the project id where the resources will be created. Check the Variables section below for more details.

In the following command, we define the project_id variable using terraform's -var option. Make sure to replace $MYPROJECT with your GCP project ID.

$ terraform init
$ terraform apply -var project_id=$MYPROJECT
[Output omitted]
Apply complete! Resources: 13 added, 0 changed, 0 destroyed.

Outputs:

ilb_ip = "10.0.1.5"

After the apply completes, terraform will output the IP address of the load balancer. You can connect to the test instance and use curl to test the load balancer. You should see an output similar to this:

user@local:~$ gcloud compute ssh --tunnel-through-iap vm-test
Last login: xxxx
user@vm-test:~$ curl 10.0.1.5
<pre>
Name: vm-snv1.europe-west1-c.c.$MYPROJECT.internal
IP: 10.0.1.4
Metadata: {
  "created-by": "projects/xxxx/regions/europe-west1/instanceGroupManagers/mig",
  "instance-template": "projects/xxxx/global/instanceTemplates/mig-template-20210518224515151200000001"
}
</pre>
user@vm-test:~$ curl 10.0.1.5
<pre>
Name: vm-tjg7.europe-west1-b.c.$MYPROJECT.internal
IP: 10.0.1.3
Metadata: {
  "created-by": "projects/xxxx/regions/europe-west1/instanceGroupManagers/mig",
  "instance-template": "projects/xxxx/global/instanceTemplates/mig-template-20210518224515151200000001"
}
</pre>
jccb@vm-test:~$

After you're finished, you can destroy all resources with terraform destroy.

Variables

name description type required default
project_id Project where resources will be created string ✓
ranges CIDR ranges for proxy and backend instances object({...}) ...
region Default region for resources string europe-west1

Outputs

name description sensitive
ilb_ip IP of the internal load balancer