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Deploy a New App

Introduction​

We use k8s to deploy our applications.
You can choose, based on your needs, to use basic k8s manifests, Kustomize or Helm Charts.

If you have access to PoliNetwork's k8s cluster (you can perform kubectl commands) you can directly deploy from your machine.
Although, this is not recommended in a production environment.
Check minikube to install a k8s cluster in your machine for testing purposes.

CD

To deploy our applications, we use ArgoCD with a Git File Generator pointing to the polinetwork-cd GitHub repo.

For more info, check out [Getting Started / Basic Knowledge]

Procedure​

  1. Deploy a Docker image
  2. Create the app structure
  3. Open a PR into polinetwork-cd
  4. Monitor deploy on ArgoCD

Create the app structure​

This is the crucial part, so make sure to follow it step-by-step.

  1. Clone polinetwork-cd repo
  2. Create a new branch (named as you like, e.g. mc-server-deploy)
  3. Create this minimal file structure:
🗀 <k8s-namespace>
├─ 🗀 src
│  └── deployment.yaml
│ 
└─ config.json
info

The <k8s-namespace> should be a slug (lowercase words separated by hyphens) identifier of the application/service you want to deploy.
You can append, if necessary, an enviornment tag (e.g. app-dev, app-prod).

Make sure that you use the same <k8s-namespace> value for both:

  • folder name
  • namespace field in k8s resources

Inside src/ you can put one of the following:

How these build tools are detected and distinguished is described here.

important

If you would like to use the Docker Image Auto-Updater, base k8s manifests are not supported, you must choose between Kustomize and Helm Chart.

For more info, check the relative section.

Docker Image Auto-Updater​

We use ArgoCD Image Updater to automatically update docker images in deployments.
This is an optional feature, but the alternative is to use a docker image fixed version (e.g. nginx:1.27.4).

We use the digest strategy by default (also the only one we documented so far).
Check out the other strategies available.

As mentioned in the section above, you must use Kustomize or Helm Charts.

warning

Consider the following manifest:

kind: Pod
apiVersion: v1
metadata:
  name: example-pod
  namespace: test
spec:
  containers:
    - name: nginx
      image: nginx:latest

the image would not update if you don't follow this guide, even though there is latest.

Digest with Kustomize​

In this configuration, we are using a Kustomize deployment with digest strategy.
These are the steps to follow: (we are using toto04/testcontainer as the docker image)

  1. Create a src/kustomization.yaml with this content:
apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization

resources:
- deployment.yaml
  1. As declared in the resources field above, we need a k8s manifest src/deployment.yaml.
    Create it and set the spec.containers[x].image field as a fixed digest, example:
spec:
  containers:
  - name: docker-test-pod
    image: toto04/testcontainer@sha256:b5ec2efcc11e90c2fd955cd1c01f3fdf7c2f18c77c213360addcd37be7e8f2f3
tip

If you are using Docker Hub, you can find a digest going to the image homepage (example) under the tag you want to use (e.g. latest)

  1. In the config.json file set the image(s) to automatically update:
  "image": {
    "image_list": "toto04/testcontainer:latest",
    "update_strategy": "digest"
  }

In this configuration, the image toto04/testcontainer would be automatically updated following the tag latest.

tip

You can also specify multiple images to update:

config.json
  "image": {
    "image_list": "x/image1:latest x/image2:latest",
    "update_strategy": "digest"
  }
src/deployment.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: deploy-1
  namespace: <k8s-namespace>
spec:
  replicas: 1
  selector:
    matchLabels:
      app: app-1
  template:
    metadata:
      labels:
        app: app-1
    spec:
      containers:
      - name: app-1-pod
        image: x/image1@sha256:xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: deploy-2
  namespace: <k8s-namespace>
spec:
  replicas: 2
  selector:
    matchLabels:
      app: app-2
  template:
    metadata:
      labels:
        app: app-2
    spec:
      containers:
      - name: app-2-pod
        image: x/image2@sha256:xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

Options​

These are some useful options you can configure by editing the config.json file.

Disable an app​

If you want to disable an app (excluding it from the git generator) you can add "disabled": true.
Example:

config.json
{
  "disabled": true
  "image": {
    "image_list": "x/image1:latest x/image2:latest",
    "update_strategy": "digest"
  }
}

To reactivate the application just remove this property or set it to false.
This configuration option is introduced with this commit.

info

In the git generator configuration the selector is set to "false" due to the limitations of matchExpression.
However, in the application's config.json you can set the disabled flag to either false or "false".