Manage agent pools with the HCP Terraform Operator v2

The HCP Terraform Operator for Kubernetes lets you create and manage HCP Terraform agents, agent pools, and tokens through a single Kubernetes custom resource.

HCP Terraform Agents let HCP Terraform communicate with isolated, private, or on-premises infrastructure. By deploying agents within a specific network segment, you can connect your environment and HCP Terraform, which lets Terraform provision and manage private infrastructure.

In this tutorial you will use the HCP Terraform Operator for Kubernetes to create and manage an HCP Terraform Agent. The operator manages the lifecycle of agents, making it easier to scale them quickly and securely.

Prerequisites

This tutorial assumes that you are familiar with the standard Terraform workflow, HCP Terraform, and basic Kubernetes usage.

For this tutorial, you will need:

• An HCP Terraform organization owner account
• kubectl
• A running Kubernetes cluster v1.16+ with the HCP Terraform Operator for Kubernetes installed

If you do not have the HCP Terraform Operator for Kubernetes installed already, follow the Deploy Infrastructure with the HCP Terraform Operator for Kubernetes tutorial through the Deploy the operator step and do not delete the Kind cluster or any of the resources created.

Clone repository

In your terminal, clone the Learn HCP Terraform Operator for Kubernetes repository.

$ git clone https://github.com/hashicorp-education/learn-terraform-kubernetes-operator

Review configuration

Navigate into the v2 directory in the repository.

$ cd learn-terraform-kubernetes-operator/v2

Navigate into the operator directory, which contains configuration files for the operator.

$ cd operator

Open the agentpool.yml file. This file defines an HCP Terraform agent pool with one agent. Replace ORGANIZATION-NAME with your own HCP Terraform organization and save the file.

apiVersion: app.terraform.io/v1alpha2
kind: AgentPool
metadata:
  name: agent-pool-demo
spec:
  organization: ORGANIZATION_NAME
  token:
    secretKeyRef:
    name: terraformrc
    key: token
  name: agent-pool-demo
  agentTokens:
    - name: agent-pool-demo-token
  agentDeployment:
    replicas: 1
    spec:
    containers:
        - name: tfc-agent
        image: "hashicorp/tfc-agent:1.13.1"

Configure HCP Terraform access

The operator authenticates to HCP Terraform using an HCP Terraform Team API token, which it accesses as a Kubernetes secret.

To create the token, navigate to your HCP Terraform organization's Settings page, then click Teams.

• If you use a free HCP Terraform organization, HCP Terraform shows the team settings for the "owners". This is the only available team and it has full access to the HCP Terraform API.

• If you use HCP Standard, Plus, or Terraform Enterprise, HCP Terraform shows the team management page. Click Create a team and name the team k8sop-agents. Under Settings permissions, enable the Manage agent pools permission. Click Update team organization access to save your settings.

Click on the API tokens option in the left navigation, and then choose the Team Tokens tab.

Click Create a team token. If you use a free HCP Terraform organization, choose the owners team. If you use HCP Standard or Plus, choose your k8sop-agents team. Choose an Expiration of 30 days and then click Create.

Click Copy token to copy the token string. You will use this token in the next section.

Copy this token and store it somewhere safe.

Create the agent pool

Create an environment variable to configure the Kubernetes namespace to deploy to named NAMESPACE and set it to edu.

$ export NAMESPACE=edu

Create a secret containing your HCP Terraform Team API token. Replace APITOKEN with the token that you created earlier.

$ kubectl create secret generic -n $NAMESPACE tfc-owner --from-literal=token=APITOKEN

Apply the AgentPool specification to the namespace.

$ kubectl apply -n $NAMESPACE -f agentpool.yml

Review the operator logs to confirm you launched the agent and agent pool.

$ kubectl logs deployment/terraform-operator-hcp-terraform-operator -n tfc-operator-system -f
2023-03-28T12:58:05Z    INFO    Reconcile Agent Pool    {"agentpool": "edu/agent-pool-demo", "msg": "status.agentPoolID is empty, creating a new agent pool"}
2023-03-28T12:58:05Z    INFO    Reconcile Agent Pool    {"agentpool": "edu/agent-pool-demo", "msg": "successfully created a new agent pool with ID apool-REDACTED"}

Verify the agent pool

Navigate to your HCP Terraform organization settings. Go to the Agents page and verify that you created a new agent pool named agent-pool-demo with one agent.

Enable autoscaling

Provide the .spec.autoscaling configuration in your AgentPool specification so that the operator scales the number of agents based on the number of pending Terraform workloads.

Open the agentpool.yml file and add the following configuration.

apiVersion: app.terraform.io/v1alpha2
kind: AgentPool
spec:
  ##...
  autoscaling:
    minReplicas: 0
    maxReplicas: 1
    targetWorkspaces:
    - name: greetings
    cooldownPeriod:
      scaleUpSeconds: 30
      scaleDownSeconds: 30

The minReplicas and maxReplicas fields define the number of agents that the operator will deploy. By default, the operator will wait 300 seconds between scaling events, but you can configure the wait time with the scaleUpSeconds and scaleDownSeconds fields.

The optional targetWorkspaces configuration takes an array of workspaces to enable autoscaling on. If you omit this field, the operator will determine when to scale the agent pods based on the load of all workspaces configured to use the agent pool. You can identify workspaces with the following identifiers:

• name: The name of the workspace (Example: greetings).
• id: The ID of the workspace (Example: ws-NUVHA9feCXzAmPHx).
• wildcardName: A pattern to search for workspace names (Example: west-development-*).

In the above example, the operator will only scale the pods for this agent pool based on the load of the greetings workspace.

Apply the updated AgentPool spec.

$ kubectl apply -n $NAMESPACE -f agentpool.yml

Open the workspace.yml file and configure the workspace to use the agent pool by adding the .spec.agentPool configuration with the agent pool name.

apiVersion: app.terraform.io/v1alpha2
kind: Workspace
spec:
  ##...
  agentPool:
    name: agent-pool-demo

Next, update the workspace executionMode and set the vale to agent.

apiVersion: app.terraform.io/v1alpha2
kind: Workspace
spec:
  ##...
  executionMode: agent

Finally, apply the updated Workspace spec.

$ kubectl apply -n $NAMESPACE -f workspace.yml

With no pending Terraform workloads, the operator automatically scales the number of agents to match the minReplicas defined in your configuration. In this case, the operator stops all running agents. Watch the pods in the operator namespace and verify that the agent pods are stopped.

$ kubectl -n $NAMESPACE get pods -w
##...
edu                   agents-of-agent-pool-demo-78477fbb6f-2bsch                     0/1     Terminating         0          9m25s

Clean up resources

First, destroy the agent pool and agent by removing the resource definition from your cluster.

$ kubectl delete -n $NAMESPACE agentpool agent-pool-demo

Next, delete the Kubernetes resources. Navigate to the root directory.

$ cd ..

Destroy the namespace, secrets, and the operator. Confirm the deletion by typing yes when prompted.

$ terraform destroy
##...
Plan: 0 to add, 0 to change, 5 to destroy.

Do you really want to destroy all resources?
  Terraform will destroy all your managed infrastructure, as shown above.
  There is no undo. Only 'yes' will be accepted to confirm.

  Enter a value: yes
##...
Destroy complete! Resources: 5 destroyed.

Finally, if you are running on Kind, delete the cluster.

$ kind delete cluster --name terraform-learn
Deleting cluster "terraform-learn" …

Next steps

In this tutorial, you used the HCP Terraform Operator for Kubernetes to create an HCP Terraform agent pool. You can modify and extend the example configuration to deploy multiple agent pools, and scale the number of agents in each agent pool.

Visit the following resources to learn more about the HCP Terraform Operator for Kubernetes.

• Read the Deploy infrastructure with the HCP Terraform Operator v2 tutorial.
• To learn more about the operator and its design, check out the hashicorp/hcp-terraform-operator repository.
• To discover more about managing Kubernetes with Terraform, review the HashiCorp Kubernetes tutorials.