On a GCP project, I have a K8s architecture including 2 clusters.

• one cluster for microservices
• one cluster for mongodb

I have tested my mongodb cluster from inside and ensured that its works as intended. What I'm trying to do now is to connect from a pod on another cluster. I'have exposed the mongo service using a node port on the mongodb cluster:

  apiVersion: v1
  kind: Service
  metadata:
    labels:
      name: mongo
    name: mongodb-service
    annotations:
        cloud.google.com/load-balancer-type: "Internal"
  spec:
    externalTrafficPolicy: Local
    ports:
    - name: port-mongodb
      port: 27017
      protocol: TCP
      targetPort: 27017
    selector:
      role: mongo
    sessionAffinity: None
    type: NodePort

With the IP of my mongodb cluster:

- cluster:
    certificate-authority-data: DATA+OMITTED
    server: https://35.240.47.130
    name: gke_myproject_europe-west1-b_mongodb

And the port of my NodePort:

mongodb-service   NodePort    10.3.248.249   <none>        27017:32752/TCP   6m

From a new pod with python into the microservice cluster (exactly the same I used to test the mongodb cluster from inside), I execute the following python script:

from pymongo import MongoClient
client = MongoClient("mongodb://login:pass@35.240.47.130:32752")
database = client["testdb"]
collection = database["testcollection"]
inserted_id = 
collection.insert_one({"moonlight":"sonata"}).inserted_id

The result is always an error:

pymongo.errors.ServerSelectionTimeoutError: mongo:32752: timed out

What am I doing wrong ?

UPDATE

Additionally, here is some nslookup tests from the microservices cluster. First, I check the mongodb NodePort service IP

root@pybbox-55bdc76ddb-nw5gm:/# nslookup 10.3.248.249
Server:     10.35.240.10
Address:    10.35.240.10#53

** server can't find 249.248.3.10.in-addr.arpa: NXDOMAIN

Also, I check if the cluster see the other using the cluster IP.

root@pybbox-55bdc76ddb-nw5gm:/# nslookup 35.240.47.130 
Server:     10.35.240.10
Address:    10.35.240.10#53

Non-authoritative answer:
130.47.240.35.in-addr.arpa  name = 130.47.240.35.bc.googleusercontent.com.

Authoritative answers can be found from: