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AWS EC2 infrastructure provider

This infrastructure provider uses Terraform to create the AWS infrastructure needed to host a Kubernetes cluster.

The provisioned infrastructure typically looks something like

HA Kubernetes in AWS

This infrastructure is created in a given AWS region (such as eu-west-2) and VPC. One can either specify an existing VPC (via ${vpc_id}) or leave it unspecified to have Terraform create a new VPC (with a given IP address range, as specified by ${vpc_address_rance}.

Some notable details on the spawned infrastructure:

  • It makes use of several availability zones, and spreads masters and worker nodes over the AZs in a round-robin manner to promote fault-tolerance. The setup illustrated in the image can withstand the loss of an entire AZ while still being operational.

  • A VPC-internal load-balancer is used to connect workers with the masters. This allows the cluster communication to remain within the cluster. The load-balancer uses health-checks to only forward traffic to working master nodes.

  • A separate internet-facing (public) load-balancer is set up to allow a cluster administrator to access the apiserver (via kubectl).

Configure

The Terraform script (main.tf) requires some input in order to provision servers. The set of parameters is quite large but most of the parameters are optional and can safely be left out.

Terraform will prompt for (missing) mandatory variables. This can be a bit tedious, and one can therefore place variables in one or more variable files which are passed with --var-file flags.

The mandatory parameters are:

  • aws_access_key: AWS Access Key ID of IAM user that will be used to run Terraform.

  • aws_secret_key: AWS Secret Access Key of IAM user that will be used to run Terraform.

  • region: The AWS region where the infrastructure is to be created. For example, eu-west-2.

  • cluster_name: A name that should describe the purpose of the cluster (for example, customer-x). Although not strictly necessary, make sure that you use a unique name for each cluster, since the cluster name will be used to tag created resources (and will help you distinguish resources belonging to different clusters).

  • vpc_id: can either be set to the ID of an existing VPC (e.g., vpc-9b716af2) or left unspecified to have Terraform create a new VPC. If a new VPC is to be created, ${vpc_address_range}, the VPC CIDR block should be specified (for instance, 10.0.0.0/16).

  • availability_zones: Describes how to set up cluster subnets across availability zones. The master and worker nodes will be assigned to AZs in a round-robin manner. Three AZs are desirable to promote a fault-tolerant setup that can withstand the loss of one availability zone.

    It could look something like (note that the AZs must be within the specified ${region} and the subnet cidr blocks must be proper subsets of the VPC's CIDR block):

      availability_zones = {
     "us-east-2a" = {
       "subnet_cidr_block" = "10.0.0.0/24"
     }

     "us-east-2b" = {
       "subnet_cidr_block" = "10.0.1.0/24"
     }

     "us-east-2c" = {
       "subnet_cidr_block" = "10.0.2.0/24"
     }
   }

  • num_masters: The number of master nodes to create. Needs to be at least three for high-availability.

  • num_workers: The number of worker nodes to create.

There are a bunch of optional arguments, most of which can safely be ignored. Notably, one can set the SSH login key to use for created VMs via ssh_private_key_path and ssh_public_key_path.

An example configuration is shown in examples/config.tfvars.

To view all available configuration options see main.tf.

Run

# initialize the working directory
terraform init infra-providers/aws

# plan the provsioning (this is a dry-run that won't execute anything)
terraform plan -var-file config.tfvars infra-providers/aws

# execute the provisioning plan
terraform apply -var-file config.tfvars infra-providers/aws

Output

When terraform apply finishes, it outputs information about the infrastructure it produced. Some of these output items need to be passed to the installer. These include:

  • master_public_ips: needs to be set in the publicIP field for each master in the cluster definition.
  • master_private_ips: needs to be set in the privateIP field for each master in the cluster definition.
  • worker_public_ips: needs to be set in the publicIP field for each worker in the cluster definition.
  • worker_private_ips: needs to be set in the privateIP field for each worker in the cluster definition.
  • master_internal_loadbalancer_fqdn: needs to be set in the masterLoadBalancerAddress field in the cluster definition.
  • master_public_loadbalancer_fqdn: needs to be added to the list of master FQDNs in masterFQDNs.

Install Kubernetes

Once all VMs have booted, it is time to run the installer (refer to the README.md).