Terraform is a great tool to programmatically define infrastructure (IaC or Infrastructure as Code) since Kubernetes Applications are containerized, its deployment can be done with a small Terraform configuration file that defines the resources that should be created in Kubernetes.
This tutorial shows how to publish an Application and create a NodePort in Kubernetes using Terraform. It only takes 10 seconds!
The application will be retrieved from the Docker Public Registry and Terraform will instruct Kubernetes to create 3 replicas and publish its services in a NodePort.
How to deploy applications in Kubernetes using Terraform
Check Kubernetes Cluster Connection Context
Check the context file using the command kubectl config view.
Test Kubernetes Cluster Connectivity
Check Kubernetes Cluster Connectivity using the command kubectl get nodes.
Create a Terraform file for Application Deployment in Kubernetes
Use the Terraform Kubernetes provider and set the config_context to use. Define a kubernetes_deployment resource with the Kubernetes metadata, specs, and container (Docker) image.
Initialize Terraform Kubernetes Provider
Initialize the Terraform Providers (Terraform Kubernetes provider) with the terraform init command. It will download the required plugins.
Publish the Application In Kubernetes and its NodePort with Terraform
Run terraform plan and terraform apply to Publish the Application In Kubernetes and create a NodePort (if needed).
Use the Kubernetes Dashboard to Review the Deployment
The Kubernetes Dashboard shows the number of replicas or PODS of the application and a Service with the NPort to access the application from outside the Kubernetes cluster.
This demo shows how Terraform is used to deploy an application image from the Docker Public Registry into Kubernetes.
Click the ► play button to see the asciinema demo:
For our example, we will use an existing Kubernetes cluster connection configuration available at the standard location ~/.kube/config
The ~/.kube/config file can have many different contexts, a context defines a cluster, a user, and a name for the context.
Check the context file using the command kubectl config view:
Zj7i2amef572KHsabWyPFnH0wSHhw80DJa3UMujA1mI3JyUYtCuqpeSceZTkNDyF3iNpcF79PrOFXfkCqLDKbZQQQ4tPGqfrxxvT7l5LSghyN1f0IjPYmARPlAbIQUisHk3clsuQOUDEA3W0gEjS2VlNh7uphTvQFh3Zj7i2amef572KHsabWyPFnH0wSHhw80DJa3UMujA1mI3JyUYtCuqpeSceZTkNDyF3iNpcF79PrOFXfkCqLDKbZQQQ4tPGqfrxxvT7l5LSghyN1f0IjPYmARPlAbIQUisHk3clsuQOUDEA3W0gEjS2VlNh7uphTvQFh3
$ kubectl config view
apiVersion: v1
clusters:
- cluster:
certificate-authority-data: DATA+OMITTED
server: https://192.168.50.11:6443
name: kubernetes
contexts:
- context:
cluster: kubernetes
user: kubernetes-admin
name: kubernetes-admin@ditwl-k8s-01
current-context: kubernetes-admin@ditwl-k8s-01
kind: Config
preferences: {}
users:
- name: kubernetes-admin
user:
client-certificate-data: REDACTED
client-key-data: REDACTED</pre>
The context named kubernetes-admin@ditwl-k8s-01 is shown as it appears at ~/.kube/config file:
apiVersion: v1
clusters:
- cluster:
certificate-authority-data: LS0tLS1CRUdJTiBDRVJUSUZJQ0FURS0tLS0tCk1JSUN5RENDQWJDZ0F3SUJBZ0lCQURBTkJna3Foa2lH....Q0VSVElGSUNBVEUtLS0tLQo=
server: https://192.168.50.11:6443
name: kubernetes
contexts:
- context:
cluster: kubernetes
user: kubernetes-admin
name: kubernetes-admin@ditwl-k8s-01
current-context: kubernetes-admin@ditwl-k8s-01
kind: Config
preferences: {}
users:
- name: kubernetes-admin
user:
client-certificate-data: LS0tLS1CRUdJTiBDRVJUSUZJQ0FURS0tLS0tCk1JSUM4akNDQWRxZ0F3SUJBZ0lJWTJsaU5WWjVrZ1V3....U4rbW9qL1l6V0NJdURnSXZBRU1NZDVIMnBOaHMvcz0KLS0tLS1FTkQgQ0VSVElGSUNBVEUtLS0tLQo=
client-key-data: LS0tLS1XRUdJTiBSU0EgUFJJVkFURSBLRVktLS0tLQpWSUlFcFFJQkFBS0NBUUVBK295RXBYVTZu.....BLRVktLS0tLQo=
We will use the context kubernetes-admin@ditwl-k8s-01 in our Terraform provider definition for Kubernetes.
If your context differs either update the Terraform file or rename the context using the commands:
kubectl config get-contexts kubectl config rename-context
In the following example, an existing context named kubernetes-admin@kubernetes is renamed to kubernetes-admin@ditwl-k8s-01
$ kubectl config get-contexts CURRENT NAME CLUSTER AUTHINFO NAMESPACE * kubernetes-admin@kubernetes kubernetes kubernetes-admin $ kubectl config rename-context kubernetes-admin@kubernetes kubernetes-admin@ditwl-k8s-01 Context "kubernetes-admin@kubernetes" renamed to "kubernetes-admin@ditwl-k8s-01". $ kubectl config get-contexts CURRENT NAME CLUSTER AUTHINFO NAMESPACE * kubernetes-admin@ditwl-k8s-01 kubernetes kubernetes-admin
Please make sure that your Kubernetes configuration file has the correct credentials by connecting to the cluster with the kubectl command.
jruiz@XPS13:~/git/github/terraform-kubernetes-deploy-app$ kubectl get nodes NAME STATUS ROLES AGE VERSION k8s-m-1 Ready master 3h33m v1.18.6 k8s-n-1 Ready <none> 3h30m v1.18.6 k8s-n-2 Ready <none> 3h27m v1.18.6
Create or download from GitHub the file terraform.tf:
# Copyright (C) 2018 - 2020 IT Wonder Lab (https://www.itwonderlab.com)
#
# This software may be modified and distributed under the terms
# of the MIT license. See the LICENSE file for details.
# -------------------------------- WARNING --------------------------------
# IT Wonder Lab's best practices for infrastructure include modularizing
# Terraform configuration.
# In this example, we define everything in a single file.
# See other tutorials for Terraform best practices for Kubernetes deployments.
# -------------------------------- WARNING --------------------------------
terraform {
required_version = "~> 0.12" #cannot contain interpolations. Means requiered version >= 0.12 and < 0.13
}
#-----------------------------------------
# Default provider: Kubernetes
#-----------------------------------------
provider "kubernetes" {
#Context to choose from the config file.
config_context = "kubernetes-admin@ditwl-k8s-01"
version = "~> 1.12"
}
#-----------------------------------------
# KUBERNETES DEPLOYMENT COLOR APP
#-----------------------------------------
resource "kubernetes_deployment" "color" {
metadata {
name = "color-blue-dep"
labels = {
app = "color"
color = "blue"
} //labels
} //metadata
spec {
selector {
match_labels = {
app = "color"
color = "blue"
} //match_labels
} //selector
#Number of replicas
replicas = 3
#Template for the creation of the pod
template {
metadata {
labels = {
app = "color"
color = "blue"
} //labels
} //metadata
spec {
container {
image = "itwonderlab/color" #Docker image name
name = "color-blue" #Name of the container specified as a DNS_LABEL. Each container in a pod must have a unique name (DNS_LABEL).
#Block of string name and value pairs to set in the container's environment
env {
name = "COLOR"
value = "blue"
} //env
#List of ports to expose from the container.
port {
container_port = 8080
}//port
resources {
limits {
cpu = "0.5"
memory = "512Mi"
} //limits
requests {
cpu = "250m"
memory = "50Mi"
} //requests
} //resources
} //container
} //spec
} //template
} //spec
} //resource
#-------------------------------------------------
# KUBERNETES DEPLOYMENT COLOR SERVICE NODE PORT
#-------------------------------------------------
resource "kubernetes_service" "color-service-np" {
metadata {
name = "color-service-np"
} //metadata
spec {
selector = {
app = "color"
} //selector
session_affinity = "ClientIP"
port {
port = 8080
node_port = 30085
} //port
type = "NodePort"
} //spec
} //resource
Lines 13 to 15 define the required version for Terraform. We will be using Terraform 0.12
Lines 21 to 25 define the config_context from the file ~/.kube/config that will be used, we will use kubernetes-admin@ditwl-k8s-01, it also sets the required version for the Terraform Kubernetes provider.
Lines 32 to 91 define a Terraform Kubernetes deployment resource named color with the following properties:
Since we use our Local Kubernetes Cluster using Vagrant and Ansible tutorial, a NodePort must be created to expose the application port outside the VirtualBox network.
Lines 97 to 112 create a NodePort that publishes app “color” port 8080 as Node Port 30085 in all Kubernetes nodes’ public IPs. See Using a NodePort in a Kubernetes Cluster on top of VirtualBox for more information.
Initialize the Terraform Kubernetes Provider by running terraform init. It will download the required plugins. This step is needed when a new provider has been added to the Terraform plan.
~/git/github/terraform-kubernetes-deploy-app$ terraform init Initializing the backend... Initializing provider plugins... - Checking for available provider plugins... - Downloading plugin for provider "kubernetes" (hashicorp/kubernetes) 1.12.0... Terraform has been successfully initialized! You may now begin working with Terraform. Try running "terraform plan" to see any changes that are required for your infrastructure. All Terraform commands should now work. If you ever set or change modules or backend configuration for Terraform,rerun this command to reinitialize your working directory. If you forget, othercommands will detect it and remind you to do so if necessary
Publish the application by applying the Terraform plan.
Run terraform plan
jruiz@XPS13:~/git/github/terraform-kubernetes-deploy-app$ terraform plan
Refreshing Terraform state in-memory prior to plan...
The refreshed state will be used to calculate this plan, but will not be
persisted to local or remote state storage.
------------------------------------------------------------------------
An execution plan has been generated and is shown below.
Resource actions are indicated with the following symbols:
+ create
Terraform will perform the following actions:
# kubernetes_deployment.color will be created
+ resource "kubernetes_deployment" "color" {
+ id = (known after apply)
+ wait_for_rollout = true
+ metadata {
+ generation = (known after apply)
+ labels = {
+ "app" = "color"
+ "color" = "blue"
}
+ name = "color-blue-dep"
+ namespace = "default"
+ resource_version = (known after apply)
+ self_link = (known after apply)
+ uid = (known after apply)
}
+ spec {
+ min_ready_seconds = 0
+ paused = false
+ progress_deadline_seconds = 600
+ replicas = 3
...
+ spec {
+ cluster_ip = (known after apply)
+ external_traffic_policy = (known after apply)
+ publish_not_ready_addresses = false
+ selector = {
+ "app" = "color"
}
+ session_affinity = "ClientIP"
+ type = "NodePort"
+ port {
+ node_port = 30085
+ port = 8080
+ protocol = "TCP"
+ target_port = (known after apply)
}
}
}
Plan: 2 to add, 0 to change, 0 to destroy.
------------------------------------------------------------------------
Note: You didn't specify an "-out" parameter to save this plan, so Terraform
can't guarantee that exactly these actions will be performed if
"terraform apply" is subsequently run.
Run terraform apply to make the necessary changes in the Kubernetes cluster:
jruiz@XPS13:~/git/github/terraform-kubernetes-deploy-app$ terraform plan
jruiz@XPS13:~/git/github/terraform-kubernetes-deploy-app$ terraform apply
An execution plan has been generated and is shown below.
Resource actions are indicated with the following symbols:
+ create
Terraform will perform the following actions:
# kubernetes_deployment.color will be created
+ resource "kubernetes_deployment" "color" {
+ id = (known after apply)
+ wait_for_rollout = true
+ metadata {
+ generation = (known after apply)
+ labels = {
+ "app" = "color"
+ "color" = "blue"
}
+ name = "color-blue-dep"
+ namespace = "default"
+ resource_version = (known after apply)
+ self_link = (known after apply)
+ uid = (known after apply)
}
+ spec {
+ min_ready_seconds = 0
+ paused = false
+ progress_deadline_seconds = 600
+ replicas = 3
...
+ template {
+ metadata {
+ generation = (known after apply)
+ labels = {
+ "app" = "color"
+ "color" = "blue"
}
+ name = (known after apply)
+ resource_version = (known after apply)
+ self_link = (known after apply)
+ uid = (known after apply)
}
+ spec {
...
+ container {
+ image = "itwonderlab/color"
+ image_pull_policy = (known after apply)
+ name = "color-blue"
+ stdin = false
+ stdin_once = false
+ termination_message_path = "/dev/termination-log"
+ tty = false
+ env {
+ name = "COLOR"
+ value = "blue"
}
+ port {
+ container_port = 8080
+ protocol = "TCP"
}
...
}
# kubernetes_service.color-service-np will be created
+ resource "kubernetes_service" "color-service-np" {
+ id = (known after apply)
...
+ spec {
+ cluster_ip = (known after apply)
+ external_traffic_policy = (known after apply)
+ publish_not_ready_addresses = false
+ selector = {
+ "app" = "color"
}
+ session_affinity = "ClientIP"
+ type = "NodePort"
+ port {
+ node_port = 30085
+ port = 8080
+ protocol = "TCP"
+ target_port = (known after apply)
}
}
}
Plan: 2 to add, 0 to change, 0 to destroy.
Do you want to perform these actions?
Terraform will perform the actions described above.
Only 'yes' will be accepted to approve.
Enter a value: yes
kubernetes_service.color-service-np: Creating...
kubernetes_service.color-service-np: Creation complete after 0s [id=default/color-service-np]
kubernetes_deployment.color: Creating...
kubernetes_deployment.color: Creation complete after 8s [id=default/color-blue-dep]
Apply complete! Resources: 2 added, 0 changed, 0 destroyed.
The application has been published.
Open the URL http://192.168.50.11:30085/ to access the Color App (All Nodes in Kubernetes expose the same NodePort, you can use any of the Cluster IPs as explained in Using a NodePort in a Kubernetes Cluster on top of VirtualBox.
Now that you have accessed one of the Color App replicas, you can explore the changes that Terraform did in Kubernetes using the Kubernetes Dashboard, you can also modify the Terraform configuration, and apply changes to the deployed application.
If using the tutorial for a local Kubernetes cluster, access the Kubernetes Dashboard with the URL https://192.168.50.11:30002/
The Dashboard shows the 3 replicas or PODS of the application, a replica set that tells Kubernetes the number of PODs that it has to keep alive, and a Service with the NPort.
See how Terraform and Kubernetes modify the application number of replicas without disturbing existing connections by using a rolling update strategy.
Modify the terraform.tf file to change the number of replicas:
replicas = 1
Run terraform plan to see what will change:
jruiz@XPS13:~/git/github/terraform-kubernetes-deploy-app$ terraform plan
Refreshing Terraform state in-memory prior to plan...
...
~ update in-place
Terraform will perform the following actions:
# kubernetes_deployment.color will be updated in-place
~ resource "kubernetes_deployment" "color" {
id = "default/color-blue-dep"
wait_for_rollout = true
metadata {
annotations = {}
generation = 1
labels = {
"app" = "color"
"color" = "blue"
}
...
~ spec {
min_ready_seconds = 0
paused = false
progress_deadline_seconds = 600
~ replicas = 3 -> 1
revision_history_limit = 10
...
strategy {
type = "RollingUpdate"
rolling_update {
max_surge = "25%"
max_unavailable = "25%"
}
}
...
}
Plan: 0 to add, 1 to change, 0 to destroy.
------------------------------------------------------------------------
Note: You didn't specify an "-out" parameter to save this plan, so Terraform
can't guarantee that exactly these actions will be performed if
"terraform apply" is subsequently run.
Run terraform apply to make the change:
jruiz@XPS13:~/git/github/terraform-kubernetes-deploy-app$ terraform apply
...
Resource actions are indicated with the following symbols:
~ update in-place
Terraform will perform the following actions:
# kubernetes_deployment.color will be updated in-place
~ resource "kubernetes_deployment" "color" {
id = "default/color-blue-dep"
wait_for_rollout = true
...
~ spec {
min_ready_seconds = 0
paused = false
progress_deadline_seconds = 600
~ replicas = 3 -> 1
revision_history_limit = 10
...
}
Plan: 0 to add, 1 to change, 0 to destroy.
...
kubernetes_deployment.color: Modifying... [id=default/color-blue-dep]
kubernetes_deployment.color: Modifications complete after 1s [id=default/color-blue-dep]
Apply complete! Resources: 0 added, 1 changed, 0 destroyed.
Terraform has instructed Kubernetes to change the number of replicas from 3 to 1, if you look at the dashboard or monitor the Kubernetes cluster during the change you will notice how Kubernetes applies a rolling update.
