This document summarizes a presentation on using the Kubernetes API effectively with Golang. The presentation introduces Kubernetes concepts like controllers and indexers. It demonstrates building blocks for Kubernetes applications like clients, stores, indexers, workqueues, and informers. It emphasizes best practices like handling errors, object relations, and accounting for multiple actors. The presentation provides code examples and links to documentation and sample controllers.

1. Gophercon Pune 2018
Using Kubernetes API
effectively with Golang

2. Vishal Biyani
CTO & Founder at InfraCloud technologies
www.infracloud.io
https://twitter.com/vishal_biyani
GDE: Google Developer Expert - Kubernetes, Google Cloud
Kubernetes Pune Meetup Organizer
https://www.meetup.com/Kubernetes-Pune/
Serverless Pune meetup Organizer
https://www.meetup.com/Serverless-Pune
Fission contributor (FaaS on Kubernetes)

3. Tomorrow 11:45 AM
Playing with robots in Golang

4. Do you use Kubernetes?
Do you develop applications which extend
Kubernetes’s capability?
Quick question

5. 1) Introduce vocabulary (What is a
controller, indexer?)
2) Explore best practices ..
For developing Kubernetes native
applications
Goals

6. Find code here:
https://github.com/vishal-biyani/
gopherconindia2018

7. Library structure
● Scheme & encoding/decoding
packages for Kubernetes API
objects
● Client code - Most of times you
will deal with tools/cache
package

8. Codetime: “Hello World”
● Authenticating with Kubernetes
Cluster
○ From outside cluster
○ In Cluster:
● Basic CRUD
Demo 1
*RBAC*

9. Kubernetes Controller
● Active Loop { desired state → Current state }
for {
desired := getDesiredState()
current := getCurrentState()
makeChanges(desired, current)
}

10. ListWatcher: List objects and watch based
on resource version
Building Blocks
Demo 2

11. Store: A way to store objects locally
Indexer: Store, with multiple indexing
functions
Building Blocks

12. Workqueue: Provide work items in order
only once, in multiple consumer/producers
RateLimitingQueue: Limit addition rate
DelayingQueue: Failed, try after X
Building Blocks

13. Building Blocks
Informer: events for changes in objects
SharedInformer: Mutiple event handlers for a
change
Reflector: Watches a ListWatcher and updates
data in Store on change

14. More codetime

15. Kubernetes is a distributed
System

16. Queue items and use multiple
workers to pick items from queue to
operate on
Queue & operate

17. On error retry with reasonable
backoff and then percolate error to
top level
On error, requeue + retry, then
error

18. Order
No latency
Not missing events
Don’t assume

19. When in doubt
Check resource version of Object, if it
has not changed, nothing has
changed.

20. Object relations
If X creates Y, then use
OwnerReference (Pod’s owner
reference is ReplicationController)

21. There are multiple actors and current
state might be changed by others too!
Multiple actors

22. ● Controllers Doc:
https://github.com/kubernetes/community/blob/ma
ster/contributors/devel/controllers.md
● Sample controllers built in Calico:
https://github.com/projectcalico/kube-controllers/tr
ee/master/pkg/controllers
● Alena’s talk at Kubecon US 2017:
https://www.youtube.com/watch?v=QIMz4V9WxVc
Learn more:

23. ধন বাদ!
Dank je!
Kiitos!
આભાર!
ध यवाद!
Grazie!
Je vous remercie!
ありがとうございました！
ਤੁਹਾਡਾ ਧੰਨਵਾਦ!
ந றி!
ధన ా ల !
ന ി!
THANK YOU!