This document discusses scaling Jenkins with Kubernetes. Previously, Jenkins was run on single EC2 instances with issues like underutilization and port collisions. The new approach runs Jenkins on Kubernetes, allowing on-demand PODs for each build with complete isolation. A modified Kubernetes plugin was created to support multiple containers and persistent volumes per POD. Builds are queued and run on Kubernetes nodes, improving scalability. Demostrating this approach saves 70-90% over running Jenkins on always-on EC2 instances by using spot instances for Kubernetes nodes.

1. Scaling Jenkins with Kubernetes 1.2

2. About me
Senior DevOps Engineer @ Glide
rubygems.org/profiles/amimahloof
Contribution to OpenSource via RubyGems and GitHub:
github.com/innovia
linkedin.com/in/amimahloof

3. Glide environment
Multiple Redis Servers
MySQL
DynamoDB
Multiple Background Queue Processors
App Server
Multiple Web Socket Servers
CloudSearch

4. Previous Jenkins setup
Single Jenkins Master machine for Server code
builds
Single Jenkins Master Machine for Android
client builds
Dedicated MySQL database per build
Dedicated port per build service
Each build environment encapsulated and
managed by Eye - process monitoring
https://github.com/kostya/eye

5. Previous Jenkins Issues
Under-utilized instances running 24/7 (expensive!)
Port collisions
Out of memory issues - build failures
Databases needed to be created and wiped per build
Debugging failed tests was extremely hard
Updating Jenkins ec2 image especially for Android was a
challenge

6. NFS-SERVER
POD EBS Volume
Scaling Jenkins with Kubernetes
Jenkins Master
BackEnd RC
Jenkins Master
Android RC
Backend
POD
Jenkins Ingress
Controller
POD
nginx configmap
Jenkins
Slave
POD
With KubeCtl
Backend Service (IP)
single elb
for both CI’s
addresses

7. Current Jenkins Kubernetes Plugin
https://github.com/jenkinsci/kubernetes-plugin
Support single docker image
(jenkins-slave docker image - it create’s a POD with that
image)
Does not support multiple containers in a POD
Does not support Persistent Volumes

8. Modified Jenkins Kubernetes Plugin
https://github.com/innovia/kubernetes-plugin
Support reading and parsing a POD template file
Support multiple containers in a POD
Support Persistant Volumes, EBS, EmptyDir, HostPath Volum
Does not support POD template per JOB
(System global config)

9. Read POD
Template
Start Build
Send POD
Object
Jenkins
Slave
POD
download JNLP file from
Jenkins Master
Connect to
Jenkins Master Slave Port
Build Flow Part 1
Pull Request

10. Build Flow Part 2
Jenkins Master Jenkins Slave
Start Job on Slave
git fetch and merge server code
create service
JOB_NAME-BUILD_NUMBER
create PV - PVC
JOB_NAME-BUILD_NUMBER
start tests
teardown
POD, SERVICE, PV, PVC
clean-up temp location
submit result to bitbucket
create POD
JOB_NAME-BUILD_NUMBER
wait for setup complete file
(check dependancies)

11. Advantages
On Demand PODs
Complete test isolation
Source controlled by developers flexible POD template
Jobs queued up in Kubernetes Scheduler until
node resources are available (running builds finish)
Scalable Kubernetes Nodes
Plugin keeps track of POD - if POD dies in the middle
it launches up a new slave for that job
Persistant Storage (EBS via NFS)
Spot instances using node selectors

12. Demo

13. Kubernetes on Spot Instances
Save 70-90% over On Demand
Managed by Spot Fleet to reduce downtime
Different fleets for different types of Kubernetes Nodes, allowing dynamic
pod allocation using Node Selector
Until implemented in Kubernetes 1.3, we have to create our own Fleets
eg.
https://github.com/kubernetes/kubernetes/issues/24472#issuecommen
t-211975112

14. Thank you!
Questions?
Slides available
http://www.slideshare.net/AmiMahloof/scaling-jenkins-with-kubernetes