kuberentes mongoDB replica set pod labeler
The problem
You have a mongoDB replica set running as a stateful set on kubernetes and you need to expose it as an external service. If you use loadbalancer
service it will select one of the mongo pods randomly so you can be redirected to a secondary node which is read only.
Solution
Use mongo labeler sidecar that will check which pod is primary and will add primary=true
label so you can use it in your service definition as a selectora.
apiVersion: v1
kind: Service
metadata:
name: mongo-external
labels:
name: mongo
spec:
type: LoadBalancer
ports:
- name: mongo
port: 27017
selector:
role: mongo
primary: "true"
Configuration
Pod labeler will aultomatically detect kubernetes config wile running inside the cluster but if you want to test it outside it assumes that your k8s config is stored in ~/.kube/config
and mongo runs on localhost:27017
You can use kubectl port-forward mongo-0 27017
command for testing purposes.
ENV
LABEL_SELECTOR - labels that describe your mongo deployment
NAMESPACE - restricts where to look for mongo pods
DEBUG - when set to true increases log verbosity
Example:
env:
- name: LABEL_SELECTOR
value: "role=mongo,environment=dev"
- name: NAMESPACE
value: "dev"
- name: DEBUG
value: "true"