How can I expose a Statefulset with a load balancer? - kubernetes

Question

I currently trying to create a cluster of X pods witch each have a personal persistent volume. To do that I've created a StateFulSet with X replicas and a PersistentVolumeClaimTemplate This part is working.
The problem is that it's seem's to be impossible to expose thoses pods with a LoadBalancer in the same way as a deployment (because of the uniqueness of a pods in a statefulset).
At this moment I've tried to expose it as a simple deployment witch is not working and the only way I've found is to expose each pods one by one (I've not tested it but I saw it on this) but it's not that scalable...
I'm not running kubernetes on any cloud provider platform then please avoid exclusive command line.

Answer 1

The problem is that it's seem's to be impossible to expose thoses pods with a LoadBalancer in the same way as a deployment (because of the uniqueness of a pods in a statefulset).
Why not? Here is my StatefulSet with default Nginx
$ k -n test get statefulset
NAME DESIRED CURRENT AGE
web 2 2 5d
$ k -n test get pods
web-0 1/1 Running 0 5d
web-1 1/1 Running 0 5d
Here is my Service type LoadBalancer which is NodePort (in fact) in case of Minikube
$ k -n test get svc
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
nginx LoadBalancer 10.110.22.74 <pending> 80:32710/TCP 5d
Let's run some pod with curl and do some requests to ClusterIP:
$ kubectl -n test run -i --tty tools --image=ellerbrock/alpine-bash-curl-ssl -- bash
bash-4.4$ curl 10.110.22.74 &> /dev/null
bash-4.4$ curl 10.110.22.74 &> /dev/null
bash-4.4$ curl 10.110.22.74 &> /dev/null
bash-4.4$ curl 10.110.22.74 &> /dev/null
Let's check out Nginx logs:
$ k -n test logs web-0
172.17.0.7 - - [18/Apr/2019:23:35:04 +0000] "GET / HTTP/1.1" 200 612 "-" "curl/7.61.0"
172.17.0.7 - - [18/Apr/2019:23:35:05 +0000] "GET / HTTP/1.1" 200 612 "-" "curl/7.61.0"
172.17.0.7 - - [18/Apr/2019:23:35:17 +0000] "GET / HTTP/1.1" 200 612 "-" "curl/7.61.0"
$ k -n test logs web-1
172.17.0.7 - - [18/Apr/2019:23:35:15 +0000] "GET / HTTP/1.1" 200 612 "-" "curl/7.61.0"
172.17.0.7 - is my pod with curl:
NAME READY STATUS RESTARTS AGE IP NODE
tools-654cfc5cdc-8zttt 1/1 Running 1 5d 172.17.0.7 minikube
Actually ClusterIP is totally enough in case of load balancing between StatefulSet's pods, because you have a list of Endpoints
$ k -n test get endpoints
NAME ENDPOINTS AGE
nginx 172.17.0.5:80,172.17.0.6:80 5d
YAMLs:
apiVersion: apps/v1beta1
kind: StatefulSet
metadata:
name: web
spec:
serviceName: "nginx"
replicas: 2
selector:
matchLabels:
app: nginx
template:
metadata:
labels:
app: nginx
spec:
containers:
- name: nginx
image: k8s.gcr.io/nginx-slim:0.8
ports:
- containerPort: 80
name: web
apiVersion: v1
kind: Service
metadata:
name: nginx
labels:
app: nginx
spec:
type: LoadBalancer
ports:
- port: 80
name: web
selector:
app: nginx