https://www.meetup.com/devday_pune/events/287898343/ The modern kubernetes cluster hosts a range of services ranging from 10 to 100. Every service with multiple pods might scale out or scale in. Further, a unified application url is exposed to outside world masking the complexity of micro-services. How does a request flow through the kubernetes and cloud infrastructure and reach a single pod? How does kubernetes networking make the request flow to the destination pod? What role do concepts like Pod IPs, cluster IP services, node port services, ingress records etc play in exposing the kubernetes applications? In this talk, we will explore Inter pod connectivity with Pod IPs. The need for kubernetes services. What is a clusterIP service? What is a nodeIP service? What is a load balancer service? Why do we need ingress records and ingress controller? How does ingress controller receive traffic? How does AWS load balancer send traffic to kubernetes services from outside of cluster (without really knowing that traffic is going to kubernetes cluster)?

1. Exploring the flow of network
traffic through kubernetes
cluster
- Prashant Kalkar

2. Agenda
Pod communication
Service types
Need for ingress
Ingress controller and Ingress resource

3. Example Services

5. Let’s start with Pod

6. How do I access pod application?

7. What do we need to access network
application?

8. We need :
- IP Address (of the node / component)
- Port (where the application is listening to / bind to)

9. But what about multiple pods per service

10. Need for multiple pods
● Auto recover the failed pods
● High Availability
● Auto scaling
● Rolling deployments

11. Multiple IPs (Single Port)

12. Colors used in Images

13. Stable Single IP

14. K8s ClusterIP Service

15. How does service know Pod IPs?

16. But, I don’t want to use IP addresses and
Ports

17. DNS and Well Known Port

18. But how to I access Application from outside
of cluster?

19. Container port mapping
docker run -p 18080:8080 amitsadafule/customer-service:1.0.0

20. Node Port Service

21. Node Port Service

22. NodePort and ClusterIP Service

23. But can we rely on Node IPs?
● Can’t just use a node IP
● Cloud nodes should be treated as ephemeral (Cattle not Pets)
● Scale In and Scale out.

24. Stable IP/DNS

25. Load balancer Service

26. What about port collision?
● In a shared cluster it will be problematic to manage NodePort.
● Services will fail if Port is not available.
● Clients don’t really rely on the NodePort for LoadBalancer type service (since
load balancer is using well known port)
Can we get rid of hardcoded port and assign free available port?

27. Service Types

28. But I have multiple services

29. Lets install products service as well.

30. We need something like this

31. That what ingress controller does

32. K8s Controllers

39. Lets add ingress resources
- Install ingress controller (I have already installed ingress controller).
- Add ingress resource for Customers Service.
- Add ingress resource for Products service.

40. How do I send traffic to Ingress Controller?

41. End to end Traffic flow

42. Thank You!
Questions?

43. Bonus - How DNS is working in K8s?