kubernetes vs openshift (routes and services)

Question

I'm new to kubernetes and openshift (came from docker swarm world) and I'm having trouble with some of kubernetes and openshift documentation especially related to route and services. I was looking for how to expose a replica set of containers externally and I've found kubernetes documentation uses a service to expose the pod while openshift uses routes. can anyone explain to me the differences?

Answer 1

There are only minor differences in tools being used. OpenShift is a Kubernetes distribution, this means it is a collection of opinionated pre-selected components. So for Ingress, OpenShift uses HAProxy to get (HTTP) traffic into the cluster. Other Kubernetes distributions maybe use the NGINX Ingress Controller or something similar.

So Services are used to loadbalance traffic inside the cluster. So when you create a ReplicaSet, you'll have multiple Pods running. To "talk" to these Pods, you typically create a Service. That Service will distribute the traffic evenly between your Pods.

So to get HTTP(S) traffic from the outside to your Service, OpenShift uses Routes (Ingress in other Kubernetes distributions):

                                            +-----+
                                        +-->+ Pod |
           +-------+       +---------+  |   +-----+
Traffic--->+ Route +------>+ Service +--+-->+ Pod |
           +-------+       +---------+  |   +-----+
                                        +-->+ Pod |
                                            +-----+

So to expose your application to the outside world, you typically create an internal Service using oc create service and then create a Route using oc expose:

# Create a new ClusterIP service named myservice
oc create service clusterip myservice --tcp=8080:8080
oc expose service myservice