loadbalancer

Deploy Kubernetes Load Balancer Service with Terraform

Why Terraform

While you could use kubectl or similar CLI-based tools mapped to API calls to manage all Kubernetes resources described in YAML files, orchestration with Terraform presents a few benefits.

• Use the same configuration language to provision the Kubernetes infrastructure and to deploy applications into it.
• drift detection: terraform plan will always present you the difference between reality at a given time and config you intend to apply.
• full lifecycle management: Terraform doesn't just initially create resources, but offers a single command to create, update, and delete tracked resources without needing to inspect the API to identify those resources.
• synchronous feedback: While asynchronous behavior is often useful, sometimes it's counter-productive as the job of identifying operation result (failures or details of created resource) is left to the user. e.g. you don't have IP/hostname of load balancer until it has finished provisioning, hence you can't create any DNS record pointing to it.
• graph of relationships: Terraform understands relationships between resources which may help in scheduling - e.g. Terraform won't try to create a service in a Kubernetes cluster until the cluster exists.

Config files of Terraform

k8s.tf & main.tf

• main.tf

variable "region" {
  default = "us-west1"
}

variable "location" {
  default = "us-west1-b"
}

variable "network_name" {
  default = "tf-gke-k8s"
}

provider "google" {
  region = var.region
}

resource "google_compute_network" "default" {
  name                    = var.network_name
  auto_create_subnetworks = false
}

resource "google_compute_subnetwork" "default" {
  name                     = var.network_name
  ip_cidr_range            = "10.127.0.0/20"
  network                  = google_compute_network.default.self_link
  region                   = var.region
  private_ip_google_access = true
}

data "google_client_config" "current" {
}

data "google_container_engine_versions" "default" {
  location = var.location
}

• k8s.tf

provider "kubernetes" {
  version = "~> 1.10.0"
  host    = google_container_cluster.default.endpoint
  token   = data.google_client_config.current.access_token
  client_certificate = base64decode(
    google_container_cluster.default.master_auth[0].client_certificate,
  )
  client_key = base64decode(google_container_cluster.default.master_auth[0].client_key)
  cluster_ca_certificate = base64decode(
    google_container_cluster.default.master_auth[0].cluster_ca_certificate,
  )
}

resource "kubernetes_namespace" "staging" {
  metadata {
    name = "staging"
  }
}

resource "google_compute_address" "default" {
  name   = var.network_name
  region = var.region
}

resource "kubernetes_service" "nginx" {
  metadata {
    namespace = kubernetes_namespace.staging.metadata[0].name
    name      = "nginx"
  }

  spec {
    selector = {
      run = "nginx"
    }

    session_affinity = "ClientIP"

    port {
      protocol    = "TCP"
      port        = 80
      target_port = 80
    }

    type             = "LoadBalancer"
    load_balancer_ip = google_compute_address.default.address
  }
}

resource "kubernetes_replication_controller" "nginx" {
  metadata {
    name      = "nginx"
    namespace = kubernetes_namespace.staging.metadata[0].name

    labels = {
      run = "nginx"
    }
  }

  spec {
    selector = {
      run = "nginx"
    }

    template {
      container {
        image = "nginx:latest"
        name  = "nginx"

        resources {
          limits {
            cpu    = "0.5"
            memory = "512Mi"
          }

          requests {
            cpu    = "250m"
            memory = "50Mi"
          }
        }
      }
    }
  }
}

output "load-balancer-ip" {
  value = google_compute_address.default.address
}

Initialize and install dependencies

• terraform init to prepare a working directory for use and is always safe to run multiple times, to bring the working directory up to date with changes in the configuration

• terraform plan to see any changes that are required for your infrastructure.

• terraform apply to apply the changes required to reach the desired state of the configuration.

Infrastructure created with Terraform