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Refresher on deploying

Deploying to Kubernetes using kubectl

To understand how Tanka works, it is important to know what steps are required for the task of deploying Grafana and Prometheus to Kubernetes:

  1. Prometheus
    • A Deployment must be created, to run the prom/prometheus image
    • Also a Service is needed for Grafana to be able to connect port 9090 of Prometheus.
  2. Grafana
    • Another Deployment is required for the Grafana server.
    • To connect to the web interface, we will be using a Service of type NodePort.

Before taking a look how Tanka can help doing so, let’s recall how to do it with plain kubectl.

Writing the yaml

kubectl expects the resources it should create in .yaml format. For Grafana:

grafana.yaml
# Grafana server Deployment
apiVersion: apps/v1
kind: Deployment
metadata:
  name: grafana
spec:
  selector:
    matchLabels:
      name: grafana
  template:
    metadata:
      labels:
        name: grafana
    spec:
      containers:
        - image: grafana/grafana
          name: grafana
          ports:
            - containerPort: 3000
              name: ui
---
# Grafana UI Service NodePort
apiVersion: v1
kind: Service
metadata:
  labels:
    name: grafana
  name: grafana
spec:
  ports:
    - name: grafana-ui
      port: 3000
      targetPort: 3000
  selector:
    name: grafana
  type: NodePort

and for Prometheus:

prometheus.yaml
# Prometheus server Deployment
apiVersion: apps/v1
kind: Deployment
metadata:
  name: prometheus
spec:
  selector:
    matchLabels:
      name: prometheus
  template:
    metadata:
      labels:
        name: prometheus
    spec:
      containers:
        - image: prom/prometheus
          name: prometheus
          ports:
            - containerPort: 9090
              name: api
---
# Prometheus API Service
apiVersion: v1
kind: Service
metadata:
  labels:
    name: prometheus
  name: prometheus
spec:
  ports:
    - name: prometheus-api
      port: 9090
      targetPort: 9090
  selector:
    name: prometheus

That’s pretty verbose, right?

Even worse, there are labels and matchers (e.g. prometheus) that need to be exactly the same scattered across the file. It’s a nightmare to debug and furthermore harms readability a lot.

Deploying to the cluster

To actually apply those resources, copy them into .yaml files and use:

Terminal window
kubectl apply -f prometheus.yaml -f grafana.yaml
deployment.apps/grafana created
deployment.apps/prometheus created
service/grafana created
service/prometheus created

Checking it worked

So far so good, but can we tell it actually did what we wanted? Let’s test that Grafana can connect to Prometheus!

Terminal window
# Temporarily forward Grafana to localhost
kubectl port-forward deployments/grafana 8080:3000

Now go to http://localhost:8080 in your browser and login using admin:admin. Then navigate to Connections > Data sources > Add new data source, choose Prometheus as type and enter http://prometheus:9090 as URL. Hit Save & Test which should yield a big green bar telling you everything is good.

Cool! This worked out well for this small example, but the .yaml files are hard to read and maintain. Especially when you need to deploy this exact same thing in dev and prod your choices are very limited.

Let’s explore how Tanka can help us here in the next section!

Cleaning up

Let’s remove everything we created to start fresh with Jsonnet in the next section:

Terminal window
kubectl delete -f prometheus.yaml -f grafana.yaml