I have a Kubernetes cluster on which I'm running a ZeroMQ broker internally. I have set up a service so that this broker can be found by pods on the cluster, using the following Helm template:
#values.yaml
zmqServiceType:
type: ClusterIP
zmqPub:
port: 31339
zmqSub:
port: 31342
zmqWsSub:
port: 31343
-----
#service.yaml
apiVersion: v1
kind: Service
metadata:
name: zmq-broker
labels:
{{ include "zmq-broker.labels" . | indent 4 }}
spec:
type: {{ .Values.zmqServiceType.type }}
ports:
- name: zmq-sub
port: {{ .Values.zmqSub.port }}
protocol: TCP
- name: zmq-pub
port: {{ .Values.zmqPub.port }}
protocol: TCP
- name: zmq-ws-sub
port: {{ .Values.zmqWsSub.port }}
protocol: TCP
externalIPs:
#Master node IP external address
- 10.2.1.100
selector:
app.kubernetes.io/name: {{ include "zmq-broker.name" . }}
app.kubernetes.io/instance: {{ .Release.Name }}
This works great within the cluster, pods are able to find the broker with no problem with the zmq endpoint "tcp://zmq-broker:".
However, I would also like to expose the zmq-broker so that it can be reached from outside the cluster.
I know I can do this very simply, by running kubectl port-forward:
kubectl port-forward <ZMQ_BROKER_POD> 31342:31342 31339:31339 31343:31343
But this has two disadvantages: It requires the kubectl port-forward command to be running all the time, and it requires one to know what pod the broker is running on a priori (plus to my understanding it is not meant for production).
What I would prefer is a way to map the outward facing ports not to the pod, but to the service, so that they will always find it no matter what the pod name is. It technically doesn't matter what physical node we connect to the internal service, but our preference is to make it the master node. We have no need for load balancing since there is only a single broker running in the system.
I had assumed all I needed was the externalIPs section in the services file, but that does not appear to be the case. The externalIPs section does indeed create a listening process on the master node, but it doesn't appear to forward TCP traffic.
Is what I'm attempting to do here possible, and if so, how?
Edit: I moved the external IP to one of the worker nodes, and it works fine, but no matter what IP I try on the master node, it won't forward traffic. Is there something special about the K8s master node that makes it not forward external IP traffic?