CODEWITHSUNDEEP
kubernetes
Reddy Bhavani Prasad
Reddy Bhavani Prasad

Reputation: 1115

How to make k8s microservice hostname generic with respect to namespace

Currently our k8s project has following use case were the namespaces are hardcoded into the values.yaml and application source codes

(apps) namespace - NS1                 

> micro-service-A1

> micro-service-A2

> micro-service-A3

(database) namespace - DB1

> mongo-service

(messaging) namespace - MB1

> kafka-zk-service

We want to run multiple sets of above services(apps, database, messaging) in unique namespaces defined by each Engineer(Developer) such that each developer can safely bring down/play-around changing the complete set belonging to him without worrying impact on other Developers' namespace.

# Developer1 (set)

(apps) namespace - Dev1   

> micro-service-A1

> micro-service-A2

> micro-service-A3

(database) namespace - Dev1_DB

> mongo-service

(messaging) namespace - Dev1_MB

> kafka-zk-service

# Developer2 (set)

(apps) namespace - Dev2                

> micro-service-A1

> micro-service-A2

> micro-service-A3

(database) namespace - Dev2_DB

> mongo-service

(messaging) namespace - Dev2_MB                     

> kafka-zk-service

What should be the configuration of the yamls & application source code such that dynamic deployment is feasible in any namespace of developers choice?

Upvotes: 2

Views: 235

Answers (2)

Jonas
Jonas

Reputation: 128807

Externalize configuration

It is good to externalize your configuration so that you can use a different configuration without building a new image.

Use a ConfigMap for configuration with address e.g. to other services or databases. See DNS for Services and Pods for adressing.

apiVersion: v1
kind: ConfigMap
metadata:
  name: config
data:
  SERVICE_A: service-a.a-namespace.svc.cluster.local
  SERVICE_B: service-b.b-namespace.svc.cluster.local
  DB: db.local

Use the values from your ConfigMap as environment variables in your app by mapping it in your Pod or Deployment in the PodTemplate

  containers:
    - name: app-container
      image: k8s.gcr.io/app-image
      env:
        - name: SERVICE_A_ADDRESS
          valueFrom:
            configMapKeyRef:
              name: config
              key: SERVICE_A
        - name: SERVICE_B_ADDRESS
          valueFrom:
            configMapKeyRef:
              name: config
              key: SERVICE_B

Service with External Name

If you want to move a service to a new namespace but keep the addressing, you can leave a Service with External Name

kind: Service
apiVersion: v1
metadata:
  name: service-a
  namespace: namespace-a
spec:
  type: ExternalName
  externalName: service-c.namespace-c.svc.cluster.local
  ports:
  - port: 80

Upvotes: 2

Devesh mehta
Devesh mehta

Reputation: 1523

You can use --namespace flag to pass the namespace while applying the config instead of hard coding it in the config file.

kubectl apply -f service.yml --namespace=test

kubectl apply -f service.yml --namespace=prod

In this way, you can use the same config file to create the service resource in different namespaces.

Upvotes: 0

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