How to expose an "election-based master and secondaries" service outside Kubernetes cluster? - mongodb

Question

I've been trying to implement a service inside Kubernetes where each Pod needs to be accessible from outside the Cluster.
The topology of my service is simple: 3 members, one of them acting as master at any time (election based); writes go to primary; reads go to secondaries. This is MongoDB replica set by the way.
They work with no issues inside the Kubernetes cluster, but from outside the only thing I have is a NodePort service type that load balances incoming connections to one of them, but I need to access each on of them, separately, depending on what I want to do from my client (write or read).
What kind of Kubernetes resource should I use to give individual access to each one of the members of my service?

Answer 1

In order to access every pod from outside you can create a separate service for each pod and use NodePort type.
Because Service uses selectors to get to available backends, you can create just one Service for a master:
apiVersion: v1
kind: Service
metadata:
name: my-master
labels:
run: my-master
spec:
type: NodePort
ports:
- port: #your-external-port
targetPort: #your-port-exposed-in-pod
protocol: TCP
selector:
run: my-master
-------------
apiVersion: apps/v1
kind: Deployment
metadata:
name: my-master
spec:
selector:
matchLabels:
run: my-master
replicas: 1
template:
metadata:
labels:
run: my-master
spec:
containers:
- name: mongomaster
image: yourcoolimage:lates
ports:
- containerPort: #your-port-exposed-in-pod
Also, you can use one Service for all your read-only replicas and this service will balance requests between all of them.
apiVersion: v1
kind: Service
metadata:
name: my-replicas
labels:
run: my-replicas
spec:
type: LoadBalancer
ports:
- port: #your-external-port
targetPort: #your-port-exposed-in-pod
protocol: TCP
selector:
run: my-replicas
---------
apiVersion: apps/v1
kind: Deployment
metadata:
name: my-replicas
spec:
selector:
matchLabels:
run: my-replicas
replicas: 2
template:
metadata:
labels:
run: my-replicas
spec:
containers:
- name: mongoreplica
image: yourcoolimage:lates
ports:
- containerPort: #your-port-exposed-in-pod
I also suggest you do not expose Pod outside of your network because of security reasons. It would be better to create strict firewall rules to restrict any unexpected connections.