K8S Deploy

Library for deploying Elixir web apps to Kubernetes. Used in combination with docker_build library.

It will build a docker image of your app, push it and then deploy it to K8S by creating a K8S Deployment, Service and Ingress for your app. It will also request a SSL cert for your app using Cert manager. This typically is used to obtain Letsencrypt certificates but can be used with other providers.

Prerequisites

• A K8S cluster with K8S >= v1.19
• The K8S cluster installed with Cert manager and a ClusterIssuer or Issuer configured.
• kubectl installed and configured to access your K8S server
• A Docker registry available for your image. Gitlab currently provides a limited free private registry.
• Pull secrets configured on in your cluster namespace to access the image on the Docker registry

Installation

Add to mix.exs:

def deps do
  [
    {:k8s_deploy, "~> 0.5.0", runtime: false, only: :dev}
  ]
end

Install and configure docker_build to build your docker image for you.

Basic Use

Add the following entry in mix.exs:

# mix.exs
  def project do
    [
      ...
      k8s_deploy: k8s_deploy(),
      ...
    ]
  end

  defp k8s_deploy do
    [
      context: "my-k8s-cluster.com", # The kubectl context name in kubectl
      image_pull_secrets: ["my-pull-secret"], # Unless a public docker image is used this must be set up before
      cert_manager_cluster_issuer: "letsencrypt-cluster-prod", # This needs to be set up before.
      host: "www.mysite.com" # HTTPS host
    ]
  end

Deploy

To build a docker image and deploy:

mix k8s.deploy

For additional options run:

mix help k8s.deploy

Advanced usage

Additional configuration

The following additional config values are available:

• :namespace - the K8S namespace to use. Must be set up before. Defaults to default.
• :cert_manager_issuer - can be used instead of :cert_manager_cluster_issuer for a namespaced issuer.
• :from_to_www_redirect? - if your want the Ingress to perform an automatic redirection from the non-www version of your site to the www version or vice versa. Defaults to true if the host starts with www. Specify the canonical version in :host.
• :env_vars - Map of environment variables that will be set in the K8S Deployment. e.g. %{"FOO" => "BAR"}. The following environment variables are automatically injected:
  • PORT - set to 4000
  • URL_HOST - set to the :host value in the config (if set)
• :migrator - Module name or mfa tuple for running migrations. See "Running Migrations" below.
• :probe_path - URL path (without host or port) to be used for a K8S container readinessProbe and livenessProbe. Specify a URL that returns a 200 without a login. In most cases "/" should be suitable. If not set, no probes are created.
• :probe_initial_delay_seconds - Used for readinessProbe and livenessProbe if a :probe_path is set. Defaults to 10.

Using a ConfigMap for environment variables

Instead of providing environment variables via the :env_vars key, you can provide a K8S ConfigMap in the deploy/k8s folder with the name configmap-prod.yaml. (If using a different environment change prod to match).

The name of the ConfigMap must match the :app_name key specified in the docker_build config, with the suffix -configmap. This will be referenced using envFrom in the Deployment.

For example:

---
apiVersion: v1
kind: ConfigMap
metadata:
  name: myapp-configmap
data:
  FOO: BAR
  FOO2: BAR2

Running migrations

To run migrations set the :migrator config key to either a module name, e.g MyApp.Release which contains a migrate/0 function, or a mfa, e.g. {MyApp.Release, :migrate, []}. You can create the necessary code by following the recommendation in Phoenix.

A K8S Job will be created using the same docker image. It will execute the migrate function and run to completion before the deploy continutes. Any ConfigMap or vars in :env_vars will be available in to the Pod container that the job creates.

Deploying without an ingress

If you omit the host field, no ingress will be deployed (unless you have a custom template - see below). You might use this if another app deploys the ingress rules for this app.

Deploying to multiple contexts

You can also specify :context as a list. All K8S resources will then be deployed to each context in turn.

Using a custom Deployment, Service or Ingress template

If you need to customise the templates beyond what the configuration options provide, you can place your own template in your project in the location deploy/k8s/{resource}-{environment}.yaml. For example deployment-prod.yaml for a custom Deployment template.

These files can include EEx templating and accept the same variables as the default templates (see priv/templates), e.g. <%= @deployment_id> or <%= @docker_image %> in the Deployment template. N.B. The @deployment_id variable is an integer so it must be quoted in your template.

TODO

• Run git push origin master:production after deploy
• Have option to ask for key press before deploying
• Support different environments e.g. mix k8s.deploy staging with an environment setting and overrides in config
• Block until deploy complete
• Check that cert issuers exist before continuing