Kubernetes services sometime no response - kubernetes

Question

My cluster contains 1 master with 3 worker nodes in which 1 POD with 2 replica sets and 1 service are created. When I try to access the service via the command curl <ClusterIP>:<port> either from 2 worker nodes, sometimes it can feedback Nginx welcome, but sometimes it gets stuck and connection refused and timeout.
I checked the Kubernetes Service, POD and endpoints are fine, but no clue what is going on. Please advise.
vagrant#k8s-master:~/_projects/tmp1$ sudo kubectl get nodes -o wide
NAME STATUS ROLES AGE VERSION INTERNAL-IP EXTERNAL-IP OS-IMAGE KERNEL-VERSION CONTAINER-RUNTIME
k8s-master Ready master 23d v1.12.2 192.168.205.10 <none> Ubuntu 16.04.4 LTS 4.4.0-139-generic docker://17.3.2
k8s-worker1 Ready <none> 23d v1.12.2 192.168.205.11 <none> Ubuntu 16.04.4 LTS 4.4.0-139-generic docker://17.3.2
k8s-worker2 Ready <none> 23d v1.12.2 192.168.205.12 <none> Ubuntu 16.04.4 LTS 4.4.0-139-generic docker://17.3.2
vagrant#k8s-master:~/_projects/tmp1$ sudo kubectl get pod -o wide --all-namespaces
NAMESPACE NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE
default my-nginx-756f645cd7-pfdck 1/1 Running 0 5m23s 10.244.2.39 k8s-worker2 <none>
default my-nginx-756f645cd7-xpbnp 1/1 Running 0 5m23s 10.244.1.40 k8s-worker1 <none>
kube-system coredns-576cbf47c7-ljx68 1/1 Running 18 23d 10.244.0.38 k8s-master <none>
kube-system coredns-576cbf47c7-nwlph 1/1 Running 18 23d 10.244.0.39 k8s-master <none>
kube-system etcd-k8s-master 1/1 Running 18 23d 192.168.205.10 k8s-master <none>
kube-system kube-apiserver-k8s-master 1/1 Running 18 23d 192.168.205.10 k8s-master <none>
kube-system kube-controller-manager-k8s-master 1/1 Running 18 23d 192.168.205.10 k8s-master <none>
kube-system kube-flannel-ds-54xnb 1/1 Running 2 2d5h 192.168.205.12 k8s-worker2 <none>
kube-system kube-flannel-ds-9q295 1/1 Running 2 2d5h 192.168.205.11 k8s-worker1 <none>
kube-system kube-flannel-ds-q25xw 1/1 Running 2 2d5h 192.168.205.10 k8s-master <none>
kube-system kube-proxy-gkpwp 1/1 Running 15 23d 192.168.205.11 k8s-worker1 <none>
kube-system kube-proxy-gncjh 1/1 Running 18 23d 192.168.205.10 k8s-master <none>
kube-system kube-proxy-m4jfm 1/1 Running 15 23d 192.168.205.12 k8s-worker2 <none>
kube-system kube-scheduler-k8s-master 1/1 Running 18 23d 192.168.205.10 k8s-master <none>
kube-system kubernetes-dashboard-77fd78f978-4r62r 1/1 Running 15 23d 10.244.1.38 k8s-worker1 <none>
vagrant#k8s-master:~/_projects/tmp1$ sudo kubectl get svc -o wide
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE SELECTOR
kubernetes ClusterIP 10.96.0.1 <none> 443/TCP 23d <none>
my-nginx ClusterIP 10.98.9.75 <none> 80/TCP 75s run=my-nginx
vagrant#k8s-master:~/_projects/tmp1$ sudo kubectl get endpoints
NAME ENDPOINTS AGE
kubernetes 192.168.205.10:6443 23d
my-nginx 10.244.1.40:80,10.244.2.39:80 101s

Answer 1

This sounds odd but it could be that one of your pods is serving traffic and the other is not. You can try shelling into the pods:
$ kubectl exec -it my-nginx-756f645cd7-rs2w2 sh
$ kubectl exec -it my-nginx-756f645cd7-vwzrl sh
You can see if they are listening on port 80:
$ curl localhost:80
You can also see if your service has the two endpoints 10.244.2.28:80 and 10.244.1.29:80.
$ kubectl get ep my-nginx
$ kubectl get ep my-nginx -o=yaml
Also, try to connect to each one of your endpoints from a node:
$ curl 10.244.2.28:80
$ curl 10.244.2.29:80