How to specify a js to be executed once (e.g. /docker-entrypoint-initdb.d/init.js)

MongoDB Percona Operator for MongoDB
1

Hi all,

I’m testing Pecona mongodb installed via operator in a k8s environment.

I would like to know if it’s possible and how to do it, set a script to be executed only one time when volume is created at its first time.

In docker-compose I do in this way:

volumes:
- type: bind
source: ${BASE_DOCKER}/db-init/mongodb/init.js
target: /docker-entrypoint-initdb.d/init.js
- mongodb_data:/data/db

Thanks in advance

2

Hi @r.gambelli and welcome to our community!

Unfortunately, in Percona Operator for MongoDB, you cannot replicate the docker-compose volumes mount in the same way. However, you can achieve the same result with an additional Kubernetes job.

  1. Store the script in a ConfigMap:
    kubectl create configmap my-mongo-init-script --from-file=init.js

  2. Create a Job that will spin up a pod, mount the ConfigMap, and use the mongo shell to connect to your new cluster and execute the script.

    apiVersion: batch/v1
kind: Job
metadata:
  name: my-mongo-init-job
spec:
  template:
    spec:
      containers:
      - name: mongo-init
        # Use a compatible mongo shell image
        image: mongo:6.0
        command:
          - "/bin/sh"
          - "-c"
          - |
            echo "Waiting for MongoDB to be ready..."
            # Wait for the service to be resolvable
            sleep 15 
            
            echo "Running init script..."
            # Get credentials from the operator-created secret
            MONGO_ROOT_USER=$(cat /etc/mongo-creds/MONGODB_ROOT_USERNAME)
            MONGO_ROOT_PASSWORD=$(cat /etc/mongo-creds/MONGODB_ROOT_PASSWORD)
            
            # Connect and run the script
            # Assumes your service is named 'my-cluster-rs0'
            mongosh "mongodb://${MONGO_ROOT_USER}:${MONGO_ROOT_PASSWORD}@my-cluster-rs0.myns.svc.cluster.local:27017/admin?replicaSet=rs0" < /scripts/init.js
            
            echo "Script execution finished."
        volumeMounts:
        - name: script-volume
          mountPath: /scripts
        - name: mongo-creds-volume
          mountPath: /etc/mongo-creds
          readOnly: true
      volumes:
      - name: script-volume
        configMap:
          name: my-mongo-init-script
      - name: mongo-creds-volume
        secret:
          secretName: my-cluster-secrets # <-- The secret created by the Percona operator
      restartPolicy: OnFailure
  backoffLimit: 4

Or something similar :slight_smile: Hope that helps to start. Alternatively, you could build your custom dockerimage based on Percona’s official ones - but that might be tricky to maintain that.

1 Like