Using a public ECR image in local Kubernetes cluster in Terraform - amazon-web-services

Question

I've setup a very simple local kubernetes cluster for development purposes, and for that I aim to pull a docker image for my pods from ECR.
Here's the code
terraform {
required_providers {
kubernetes = {
source = "hashicorp/kubernetes"
version = ">= 2.0.0"
}
}
}
provider "kubernetes" {
config_path = "~/.kube/config"
}
resource "kubernetes_deployment" "test" {
metadata {
name = "test-deployment"
namespace = kubernetes_namespace.test.metadata.0.name
}
spec {
replicas = 2
selector {
match_labels = {
app = "MyTestApp"
}
}
template {
metadata {
labels = {
app = "MyTestApp"
}
}
spec {
container {
image = "public ECR URL" <--- this times out
name = "myTestPod"
port {
container_port = 4000
}
}
}
}
}
}
I've set that ECR repo to public and made sure that it's accessible. My challenge is that in a normal scenario you have to login to ECR in order to retrieve the image, and I do not know how to achieve that in Terraform. So on 'terraform apply', it times out and fails.
I read the documentation on aws_ecr_repository, aws_ecr_authorization_token,Terraform EKS module and local-exec, but none of them seem to have a solution for this.
Achieving this in a Gitlab pipeline is fairly easy, but how can one achieve this in Terraform? how can I pull an image from a public ECR repo for my local Kubernetes cluster?

Answer 1

After a while, I figured out the cleanest way to achieve this;
First retrieve your ECR authorization token data;
data "aws_ecr_authorization_token" "token" {
}
Second, create a secret for your kubernetes cluster**:
resource "kubernetes_secret" "docker" {
metadata {
name = "docker-cfg"
namespace = kubernetes_namespace.test.metadata.0.name
}
data = {
".dockerconfigjson" = jsonencode({
auths = {
"${data.aws_ecr_authorization_token.token.proxy_endpoint}" = {
auth = "${data.aws_ecr_authorization_token.token.authorization_token}"
}
}
})
}
type = "kubernetes.io/dockerconfigjson"
}
Bear in mind that the example in the docs base64 encodes the username and password. The exported attribute authorization_token does the same thing.
Third, once the secret is created, you can then have your pods use it as the image_pull_secrets:
resource "kubernetes_deployment" "test" {
metadata {
name = "MyTestApp"
namespace = kubernetes_namespace.test.metadata.0.name
}
spec {
replicas = 2
selector {
match_labels = {
app = "MyTestApp"
}
}
template {
metadata {
labels = {
app = "MyTestApp"
}
}
spec {
image_pull_secrets {
name = "docker-cfg"
}
container {
image = "test-image-URL"
name = "test-image-name"
image_pull_policy = "Always"
port {
container_port = 4000
}
}
}
}
}
depends_on = [
kubernetes_secret.docker,
]
}
Gotcha: the token expires after 12 hours, so you should either write a bash script that updates your secret in the corresponding namespace, or you should write a Terraform provisioner that gets triggered every time the token expires.
I hope this was helpful.