task-6-move-api-to-another-namespace

Task 6 - Move API to another namespace

flowchart LR
  User[User Browser]

  subgraph K8s[Kubernetes Cluster]
    subgraph NS_default["default"]
      FE[blog-frontend]
      REDIS[redis]
    end

    subgraph NS_new["new-ns"]
      API[blog-api]
      JOB[image-job]
    end
  end

  User -->|HTTP| FE
  FE -->|Serve html and js| User
  FE -->|HTTP| API
  API -.->|create job| JOB
  API -->|read and write| REDIS
  JOB -->|read and write image| REDIS

  style API fill:#ffcc00,stroke:#333,stroke-width:2px,color:#000,font-weight:bold

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Namespaces in Kubernetes are a way to organize resources in a cluster, such as splitting environments across teams, deployment environments (dev, QA, prod etc), or just for another reason group related resources together.

It is also possible to apply certain rules on namespaces as a whole, so it acts as a way to select multiple resources.

So far we have all our resources in the default namespace. In this task we will move the API deployment to another namespace.

We will first delete the existing API deployment in the default namespace.

We delete the deployment and related resources in the default namespace with

kubectl delete -f api.yaml -f sa.yaml -f api-svc.yaml -f job-role.yaml -f job-binding.yaml

To create the new namespace do

kubectl create namespace new-ns --dry-run=client -o yaml > new-ns.yaml

and apply it

kubectl apply -f new-ns.yaml

We can now update the API deployment to be in the new-ns

Update api.yaml so that the metadata section has namespace: new-ns

metadata:
  creationTimestamp: null
  labels:
    app: my-api
  name: my-api
  namespace: new-ns

Additionally add namespace: new-ns in metadata section of

• api-svc.yaml
• sa.yaml
• job-role.yaml
• job-binding.yaml

We also need to specify the correct namespace for the service account in job-binding.yaml

Update the namespace for the service account job-runner from namespace: default to namespace: new-ns in job-binding.yaml

subjects:
- kind: ServiceAccount
  name: job-runner
  namespace: default

and apply everything with

kubectl apply -f .

where ´.´ means all files in the current directory

We can now check that the pods run with

kubectl get pods -n new-ns

Our app does still not work though. Services can have the same name across namespaces, so to differentiate between services from different namespaces we also have to provide this in the URI.

In frontend.yaml update

http://my-api-service:8050

to

http://my-api-service.new-ns.svc.cluster.local:8050

for the UPSTREAM_API environment var.

The Redis deployment is still in the default namespace, and we need to specify the long version of the service URI in api.yaml since they are no longer in the same namespace.

The application defaulted to redis:6379 but now we need to provide in api.yaml the env var for Redis URI with

      containers:
      - image: blog-api:0.1
        name: my-blog-api
        resources: {}
        env:
        - name: REDIS_ADDR
          value: redis.default.svc.cluster.local:6379

Apply all files again:

kubectl apply -f .

After these updates the app should now be working again

Verify solution

From the workdir folder run

git diff --no-index . ../tasks/task-6-move-api-to-another-namespace/solution

and check that there is no diff

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