c12s-kubespray/contrib/terraform/packet

Kubernetes on Packet with Terraform

Provision a Kubernetes cluster with Terraform on Packet.

Status

This will install a Kubernetes cluster on Packet bare metal. It should work in all locations and on most server types.

Approach

The terraform configuration inspects variables found in variables.tf to create resources in your Packet project. There is a python script that reads the generated.tfstate file to generate a dynamic inventory that is consumed by cluster.yml to actually install Kubernetes with Kubespray.

Kubernetes Nodes

You can create many different kubernetes topologies by setting the number of different classes of hosts.

• Master nodes with etcd: number_of_k8s_masters variable
• Master nodes without etcd: number_of_k8s_masters_no_etcd variable
• Standalone etcd hosts: number_of_etcd variable
• Kubernetes worker nodes: number_of_k8s_nodes variable

Note that the Ansible script will report an invalid configuration if you wind up with an even number of etcd instances since that is not a valid configuration. This restriction includes standalone etcd nodes that are deployed in a cluster along with master nodes with etcd replicas. As an example, if you have three master nodes with etcd replicas and three standalone etcd nodes, the script will fail since there are now six total etcd replicas.

Requirements

• Install Terraform
• Install dependencies: sudo pip install -r requirements.txt
• Account with Packet Host
• An SSH key pair

SSH Key Setup

An SSH keypair is required so Ansible can access the newly provisioned nodes (bare metal Packet hosts). By default, the public SSH key defined in cluster.tf will be installed in authorized_key on the newly provisioned nodes (~/.ssh/id_rsa.pub). Terraform will upload this public key and then it will be distributed out to all the nodes. If you have already set this public key in Packet (i.e. via the portal), then set the public keyfile name in cluster.tf to blank to prevent the duplicate key from being uploaded which will cause an error.

If you don't already have a keypair generated (~/.ssh/id_rsa and ~/.ssh/id_rsa.pub), then a new keypair can be generated with the command:

ssh-keygen -f ~/.ssh/id_rsa

Terraform

Terraform will be used to provision all of the Packet resources with base software as appropriate.

Configuration

Inventory files

Create an inventory directory for your cluster by copying the existing sample and linking the hosts script (used to build the inventory based on Terraform state):

$ cp -LRp contrib/terraform/packet/sample-inventory inventory/$CLUSTER
$ cd inventory/$CLUSTER
$ ln -s ../../contrib/terraform/packet/hosts

This will be the base for subsequent Terraform commands.

Packet API access

Your Packet API key must be available in the PACKET_AUTH_TOKEN environment variable. This key is typically stored outside of the code repo since it is considered secret. If someone gets this key, they can startup/shutdown hosts in your project!

For more information on how to generate an API key or find your project ID, please see: https://support.packet.com/kb/articles/api-integrations

The Packet Project ID associated with the key will be set later in cluster.tf.

For more information about the API, please see: https://www.packet.com/developers/api/

Example:

$ export PACKET_AUTH_TOKEN="Example-API-Token"

Note that to deploy several clusters within the same project you need to use terraform workspace.

Cluster variables

The construction of the cluster is driven by values found in variables.tf.

For your cluster, edit inventory/$CLUSTER/cluster.tf.

The cluster_name is used to set a tag on each server deployed as part of this cluster. This helps when identifying which hosts are associated with each cluster.

While the defaults in variables.tf will successfully deploy a cluster, it is recommended to set the following values:

• cluster_name = the name of the inventory directory created above as $CLUSTER
• packet_project_id = the Packet Project ID associated with the Packet API token above

Enable localhost access

Kubespray will pull down a Kubernetes configuration file to access this cluster by enabling the kubeconfig_localhost: true in the Kubespray configuration.

Edit inventory/$CLUSTER/group_vars/k8s-cluster/k8s-cluster.yml and comment back in the following line and change from false to true: \# kubeconfig_localhost: false becomes: kubeconfig_localhost: true

Once the Kubespray playbooks are run, a Kubernetes configuration file will be written to the local host at inventory/$CLUSTER/artifacts/admin.conf

Terraform state files

In the cluster's inventory folder, the following files might be created (either by Terraform or manually), to prevent you from pushing them accidentally they are in a .gitignore file in the terraform/packet directory :

• .terraform
• .tfvars
• .tfstate
• .tfstate.backup

You can still add them manually if you want to.

Initialization

Before Terraform can operate on your cluster you need to install the required plugins. This is accomplished as follows:

$ cd inventory/$CLUSTER
$ terraform init ../../contrib/terraform/packet

This should finish fairly quickly telling you Terraform has successfully initialized and loaded necessary modules.

Provisioning cluster

You can apply the Terraform configuration to your cluster with the following command issued from your cluster's inventory directory (inventory/$CLUSTER):

$ terraform apply -var-file=cluster.tf ../../contrib/terraform/packet
$ export ANSIBLE_HOST_KEY_CHECKING=False
$ ansible-playbook -i hosts ../../cluster.yml

Destroying cluster

You can destroy your new cluster with the following command issued from the cluster's inventory directory:

$ terraform destroy -var-file=cluster.tf ../../contrib/terraform/packet

If you've started the Ansible run, it may also be a good idea to do some manual cleanup:

• remove SSH keys from the destroyed cluster from your ~/.ssh/known_hosts file
• clean up any temporary cache files: rm /tmp/$CLUSTER-*

Debugging

You can enable debugging output from Terraform by setting TF_LOG to DEBUG before running the Terraform command.

Ansible

Node access

SSH

Ensure your local ssh-agent is running and your ssh key has been added. This step is required by the terraform provisioner:

$ eval $(ssh-agent -s)
$ ssh-add ~/.ssh/id_rsa

If you have deployed and destroyed a previous iteration of your cluster, you will need to clear out any stale keys from your SSH "known hosts" file ( ~/.ssh/known_hosts).

Test access

Make sure you can connect to the hosts. Note that Container Linux by CoreOS will have a state FAILED due to Python not being present. This is okay, because Python will be installed during bootstrapping, so long as the hosts are not UNREACHABLE.

$ ansible -i inventory/$CLUSTER/hosts -m ping all
example-k8s_node-1 | SUCCESS => {
    "changed": false,
    "ping": "pong"
}
example-etcd-1 | SUCCESS => {
    "changed": false,
    "ping": "pong"
}
example-k8s-master-1 | SUCCESS => {
    "changed": false,
    "ping": "pong"
}

If it fails try to connect manually via SSH. It could be something as simple as a stale host key.

Deploy Kubernetes

$ ansible-playbook --become -i inventory/$CLUSTER/hosts cluster.yml

This will take some time as there are many tasks to run.

Kubernetes

Set up kubectl

• Install kubectl on the localhost.

• Verify that Kubectl runs correctly

kubectl version

• Verify that the Kubernetes configuration file has been copied over

cat inventory/alpha/$CLUSTER/admin.conf

• Verify that all the nodes are running correctly.

kubectl version
kubectl --kubeconfig=inventory/$CLUSTER/artifacts/admin.conf  get nodes

What's next

Try out your new Kubernetes cluster with the Hello Kubernetes service.