Expose deployment via service type Node Port on digital Ocean Kubernetes - kubernetes

Question

I'm implementing a solution in Kubernetes for several clients, and I want to monitoring my cluster with Prometheus. However, because this can scale quickly, and I want to reduce costs, I will use Federation for Prometheus, to scrape different clusters of Kubernetes, but I need to expose my Prometheus deployment.
I already have that working with a service type LoadBalancer exposing my Prometheus deployment, but this approach add this extra expense to my infra structure (Digital Ocean LB).
Is it possible to make this using a service type NodePort, exposing a port to my Cluster IP, something like this:
XXXXXXXXXXXXXXXX.k8s.ondigitalocean.com:9090
Where I can use this URL to my master Prometheus scrappe all "slaves" Prometheus instances?
I already tried, but I can't reach my cluster port. Something is blocking. I also delete my firewall, to ensure that nothing is interferes in this implementation but nothing.
This is my service:
Name: my-nodeport-service
Namespace: default
Labels: <none>
Annotations: kubectl.kubernetes.io/last-applied-configuration:
{"apiVersion":"v1","kind":"Service","metadata":{"annotations":{},"name":"my-nodeport-service","namespace":"default"},"spec":{"ports":[{"na...
Selector: app=nginx
Type: NodePort
IP: 10.245.162.125
Port: http 80/TCP
TargetPort: 80/TCP
NodePort: http 30800/TCP
Endpoints: 10.244.2.220:80
Session Affinity: None
External Traffic Policy: Cluster
Events: <none>
Can anybody help me please?
---
This is my service:
```kubectl describe service my-nodeport-service
Name: my-nodeport-service
Namespace: default
Labels: <none>
Annotations: kubectl.kubernetes.io/last-applied-configuration:
{"apiVersion":"v1","kind":"Service","metadata":{"annotations":{},"name":"my-nodeport-service","namespace":"default"},"spec":{"ports":[{"na...
Selector: app=nginx
Type: NodePort
IP: 10.245.162.125
Port: http 80/TCP
TargetPort: 80/TCP
NodePort: http 30800/TCP
Endpoints: 10.244.2.220:80
Session Affinity: None
External Traffic Policy: Cluster
Events: <none>

Answer 1

You can then set up host XXXXXXXXXXXXXXXX.k8s.ondigitalocean.com:9090 to act as your load balancer with Nginx.
Try setup Nginx TCP load balancer.
Note: You will be using Nginx stream and if you want to use open source Nginx and not Nginx Plus, then you might have to compile your own Nginx with -with-stream option.
Example config file:
events {
worker_connections 1024;
}
stream {
upstream stream_backend {
server dhcp-180.example.com:446;
server dhcp-185.example.com:446;
server dhcp-186.example.com:446;
server dhcp-187.example.com:446;
}
server {
listen 446;
proxy_pass stream_backend;
}
After runing Nginx, test results should be like:
Host lb.example.com acts as load balancer with Nginx.
In this example Ngnix is configured to use round-robin and as you can see, every time a new connection ends up to a different host/container.
Note: the container hostname is same as the node hostname this is due to the hostNetwork.
There are some drawbacks of this solution like:
defining hostNetwork reserves the host’s port(s) for all the containers running in the pod
creating one load balancer you have single point of failure
every time a new node is added or removed to the cluster, the load balancer should be updated
This way, one could set up a kubernetes cluster to Ingress-Egress TCP connections routing from/to outside of the cluster.
Useful post: load-balancer-tcp.
NodePort documentation: nodePort.