Snapshot on Kubernetes¶

GitOps needs the desired state written down as files in Git. In Kubernetes, those files are manifests. This lesson writes the manifests for Snapshot and commits them, so that in the next lessons Argo CD has something to sync. 📄

ℹ️ This lesson touches Kubernetes directly. For the full depth on Deployments, Services, and multi-tier apps, see the Kubernetes course. Here we write just enough to drive the GitOps loop.

What we will do (in very simple steps)¶

1. Decide where the manifests live
2. Write a Deployment and a Service for Snapshot
3. Commit them as the desired state

Where the manifests live¶

We will keep them in a k8s/ folder inside your snapshot-app repository. That is simple and works well for learning.

💡 Larger teams often keep manifests in a separate config repository, so application code and deployment config have their own histories. The GitOps idea is the same either way.

Step 1: Write the Deployment¶

In your snapshot-app repo, create k8s/deployment.yaml:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: snapshot
  labels:
    app: snapshot
spec:
  replicas: 2
  selector:
    matchLabels:
      app: snapshot
  template:
    metadata:
      labels:
        app: snapshot
    spec:
      containers:
        - name: snapshot
          image: ghcr.io/YOUR_USERNAME/snapshot-app:v1.3.0
          ports:
            - containerPort: 5000

This declares that the cluster should keep two copies of your snapshot-app:v1.3.0 image running. Replace YOUR_USERNAME with yours, and make sure the image tag matches a version you published.

Step 2: Write the Service¶

Create k8s/service.yaml:

apiVersion: v1
kind: Service
metadata:
  name: snapshot
spec:
  selector:
    app: snapshot
  ports:
    - port: 80
      targetPort: 5000

The Service sends traffic on port 80 to the app's port 5000. The selector: app: snapshot is what links it to the Deployment, whose pods carry the same label.

Step 3: Commit the desired state¶

git add k8s/
git commit -m "Add Kubernetes manifests for Snapshot"
git push

That is the important shift. These files now are the source of truth for what should run. In the next lessons, Argo CD will read this k8s/ folder and make the cluster match it.

Going further: the full stack¶

For a complete Snapshot on Kubernetes, you would also add manifests for the database (a StatefulSet with storage, and a secret for its password) and the frontend (a Deployment, a Service, and its config). Those bring in Kubernetes concepts covered fully in the Kubernetes course. The single Deployment above is enough to learn GitOps here.

✅ Checkpoint¶

You are ready for the next lesson if:

• You have k8s/deployment.yaml and k8s/service.yaml in your repo
• The image name and tag match a version you actually published
• The manifests are committed and pushed

🩹 Common hiccups¶

• Image will not pull later: the image must be reachable. Keep the ghcr package public, or your cluster will need pull credentials.
• Selector and labels do not match: the Service selector must match the labels on the Deployment's pods. Both use app: snapshot here.
• Wrong image tag: the tag must be one you published. Check your Packages if unsure.

Next up: Install Argo CD, where you add the GitOps agent to your cluster.