Services

When you create a deployment with multiple replicas, you have an address for each replica of a container. A service consolidates all of that much like a load balancer into a single IP address. In addition, these pods may go up and down due to rolling updates and failure recovery. The service provides a stable route to available pods.

The service must specify a selector - a set of labels that identify the pods that will be “load balanced” by the service.

Here is a sample YAML file describing a service:

apiVersion: v1
kind: Service
metadata:
  name: tomcat-svc-dev
  labels:
        svc: tomcat
        env: dev
spec:
  type: ClusterIP
  ports:
  - port: 8080
    targetPort: 8080
    protocol: TCP
  selector:
        app: tomcat
        env: dev

Note: It is important to understand that the selector, which is a list of name/value pairs, must match the name/value pairs in the label of the deployments. Here is a description of a matching deployment:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: tomcat-dev
spec:
  replicas: 1
  selector:
    matchLabels:
      app: tomcat
      env: dev
  strategy:
    type: RollingUpdate
    rollingUpdate:
      maxSurge: 1
      maxUnavailable: 1
  minReadySeconds: 5
  template:
    metadata:
      labels:                           # Labels assigned to the pod.  This is useful to find pods by label.
        app: tomcat
        env: dev
    spec:
      containers:
      - name: tomcat
        image: tomcat:7
        ports:
          - containerPort: 8080
        env:
          - name: DS_URL
            valueFrom:
              secretKeyRef:
                name: tomcat-dev
                key: url
          - name: DS_USR
            valueFrom:
              secretKeyRef:
                name: tomcat-dev
                key: username
          - name: DS_PWD
            valueFrom:
              secretKeyRef:
                name: tomcat-dev
                key: password

Here is a sample of a deployment with services:

from k9.core import (
    set_default_namespace,
    create_namespace,
    create_secret,
    create_deployment,
    create_service,
    read_yaml
)

# Create namespace
set_default_namespace("service-unit-test")
create_namespace()

# Create secret - don't save passwords in source code
# for real systems - this is just an example.  See
# documentation on Secrets.
secret_name = "tomcat-dev"
secrets = {
    'url': 'https://some/url',
    'password': 'My1SecretPassword',
    'username': 'postgres'
}
create_secret(secret_name, secrets)

# create deployment
body = read_yaml('tomcat-deploy-dev.yml')
create_deployment(body)

# create service
body = read_yaml('tomcat-svc-dev.yml')
create_service(body)

k9.core.list_services(namespace: Optional[str] = None)

Lists the services in the namespace.

Parameters

namespace – Namespace to list services from. If None, default namespace will be used.

Returns

List of dictionaries with name, type, cluster-ip, external-ips, ports, and age

k9.core.service_exists(name: str, namespace: Optional[str] = None)

Checks existence of specified service.

Parameters

• name – Name of service.

• namespace – Namespace to get service from. If None, will use default namespace.

Returns

True if service exists.

k9.core.get_service(name: str, namespace: Optional[str] = None)

Retrieves details on the specified service.

Parameters

• name – Name of service to get.

• namespace – Namespace to get service from. If None, will use default namespace.

Returns

V1Service

k9.core.create_service(body: dict, namespace: Optional[str] = None)

Creates a service based on definition provided by body.

Parameters

• body – Service description: https://github.com/kubernetes-client/python/blob/master/kubernetes/docs/V1Service.md

• namespace – Namespace to create service in. If None, will use default namespace.

Returns

V1Service

You’ll most likely create a YAML file to describe your service and read that in. You can use read_yaml() to generate the body as follows:

Example:

result = create_service(read_yaml('my-service.yaml'))

Sample YAML file:

apiVersion: v1
kind: Service
metadata:
  name: tomcat-svc-dev
  labels:
        svc: tomcat
        env: dev
spec:
  type: ClusterIP
  ports:
  - port: 8080
    targetPort: 8080
    protocol: TCP
  selector:
        app: tomcat
        env: dev

k9.core.delete_service(name: str, namespace: Optional[str] = None)

Deletes the specified service. This function will check whether the service exists before attempting the delete.

Parameters

• name – Name of service to delete

• namespace – Namespace to delete from. If None, default namespace is used.

Returns

None if service doesn’t exist, otherwise V1Status