Making kubernetes simple for developers

Making
Kubernetes
Simple for
Developers
Suraj Deshmukh

About me: ● Works for Red Hat in Developer Tools team
● Contributes to Kompose, OpenCompose, Kubernetes,
OpenShift, etc.
● IRC, slack - surajd
● Twitter - surajd_
● Github - surajssd
● Email - surajd.service@gmail.com

This talk is going to have a lot of references to Kubernetes or OpenShift and
Docker Compose.
Disclaimer

Story of today’s developer (YMMV)

Deploy application in containers

Learn docker*
* Now called moby

How do I run “stuff” with docker?
$ docker run hello-world
$ docker run -p 5432:5432 postgres
First steps with Docker

Code is local python application:
(venv) $ ls
myapp.py requirements.txt
(venv) $ python myapp.py

What do you need to package your
application?
● A Dockerfile, here I am copying code from my machine to the container doing builds
locally.
FROM centos
RUN yum install -y python-pip3
COPY . /code
WORKDIR /code
RUN cd /code && pip install -r requirements.txt
CMD [ “myapp” ]
● And few commands
Note: Don’t try this in production :p

My code repo ...
$ ls
Dockerfile
myapp.py
README.md
requirements.txt

Run my awesome application
$ docker build -t myapp .
$ docker run -p 8080:8080 myapp
$ curl localhost:8080

Need to add one more service
$ ls
apiserver.py
Dockerfile.apiserver
Dockerfile.myapp
myapp.py
README.md
requirements.txt

And to bring this all up
$ docker build -t myapp -f Dockerfile.myapp .
$ docker build -t apiserver -f Dockerfile.apiserver .
$ docker run postgres
$ docker run apiserver
$ docker run -p 8080:8080 myapp

I write everything in a docker-compose file, which looks like this:
services:
postgresql:
image: postgresql
apiserver:
build: Dockerfile.apiserver
env:
POSTGRESQL_HOST: postgresql
myapp:
build: Dockerfile.myapp

Updated code repo ...
$ ls
apiserver.py
docker-compose.yml
Dockerfile.apiserver
Dockerfile.myapp
myapp.py
README.md
requirements.txt

$ docker-compose up

Docker-compose is easier for development
I am happy (Not for long).

Now that everything is running locally, how and
where do I deploy this?

Container orchestrators
● Kubernetes ( OpenShift )
● Docker Swarm
● Mesos

● Docker Compose I can use with Docker Swarm only
● Cannot use the docker-compose as is with swarm

● Kubernetes is robust
● Has Google’s production experience of more than a decade
● Huge contributor base and community

● Lot of new concepts for someone new in this world
● Pods, Service, Deployment, ReplicaSets etc.
● And what happened to all the investment I made with Docker Compose?

services:
postgresql:
image: postgresql
apiserver:
build: Dockerfile.apiserver
env:
POSTGRESQL_HOST: postgresql
myapp:
build: Dockerfile.myapp
Remember this?

More google search
I want to make my life
easier

Kompose helps me with
● Generating Kubernetes configurations.
● Defaults generated by Kompose are good enough.
● Kompose helps as long as the Docker Compose syntax helps
● But we don’t stop at good enough, do we? :)

● Works as long as I have fewer services and generic use cases.
● My application is now more than just application and database
containers.

Use cases where kompose cannot do
anything:
● Define service type.
● Kubernetes Jobs
● Secrets and Configmaps cannot be defined.
● Difficult to define volumes info.
● No way to define liveness probes and readiness probes
● How to club multiple containers in single pod
● Generating openshift templates directly.

● Most of the things (from previous slide) can be done, but needs changes
in docker-compose.yaml
● May not break application.

● No direct mapping to any docker-compose constructs
● Kompose exploits docker-compose restart.
Kubernetes Jobs

Secrets and Configmaps
● No direct mapping to any docker-compose constructs
● But other ways of doing it.
service:
foo:
Env:
SECRET: devenv
service:
foo:
Env:
SECRET: prodenv

Volumes
● Kompose assumes some size for PVC

Ingress and Routes
● No direct mapping in docker-compose world
● Hack around with labels :
labels:
kompose.service.expose: "counter.example.com"

Liveness probe and Readiness probe
● No equivalent concept in docker-compose

Kubernetes Service type
● Here also there is no direct mapping in docker-compose world to do so.
● More hacking with labels :
labels:
kompose.service.type: nodeport

So what do I do to get around it?
● Generate configs with Kompose
● Edit configs yourself to fill in the gaps

kind: List
apiVersion: v1
metadata: {}
items:
- kind: Service
apiVersion: v1
metadata:
name: etherpad
creationTimestamp:
labels:
service: etherpad
spec:
ports:
- name: '80'
protocol: TCP
port: 80
targetPort: 9001
selector:
service: etherpad
status:
loadBalancer: {}
- kind: Service
apiVersion: v1
metadata:
name: mariadb
creationTimestamp:
labels:
service: mariadb
spec:
ports:
- name: '3306'
protocol: TCP
port: 3306
targetPort: 3306
selector:
service: mariadb
status:
loadBalancer: {}
- kind: Deployment
apiVersion: extensions/v1beta1
metadata:
name: etherpad
creationTimestamp:
spec:
replicas: 1
template:
metadata:
creationTimestamp:
labels:
service: etherpad
spec:
containers:
- name: etherpad
image: centos/etherpad
ports:
- containerPort: 9001
protocol: TCP
env:
- name: DB_DBID
value: etherpad
- name: DB_HOST
value: mariadb
- name: DB_PASS
value: etherpad
- name: DB_PORT
value: '3306'
- name: DB_USER
value: etherpad
resources: {}
restartPolicy: Always
strategy: {}
status: {}
- kind: Deployment
apiVersion: extensions/v1beta1
metadata:
name: mariadb
creationTimestamp:
spec:
replicas: 1
template:
metadata:
creationTimestamp:
labels:
service: mariadb
spec:
volumes:
- name: mariadb-claim0
persistentVolumeClaim:
claimName: mariadb-claim0
containers:
- name: mariadb
image: centos/mariadb
ports:
- containerPort: 3306
protocol: TCP
env:
- name: MYSQL_DATABASE
value: etherpad
- name: MYSQL_PASSWORD
value: etherpad
- name: MYSQL_ROOT_PASSWORD
value: etherpad
- name: MYSQL_USER
value: etherpad
resources: {}
volumeMounts:
- name: mariadb-claim0
mountPath: "/var/lib/mysql"
restartPolicy: Always

As a kompose developer ...
● It’s tempting to extend docker-compose, which is done right now with
labels.
● Need to build a solution that overcomes docker-compose limitations with
respect to Kubernetes

What is OpenCompose?
● OpenCompose is a declarative higher level abstraction for specific
Kubernetes resources.
● Simple for developers to comprehend use it in their day to day
development workflow.
● Kubernetes resources define how to deploy an application,
OpenCompose tries to stick to define application only.

Sample OpenCompose file
version: '0.1-dev'
services:
- name: database
replicas: 2
containers:
- image: mariadb:10
env:
- MYSQL_ROOT_PASSWORD=rootpasswd
- MYSQL_DATABASE=wordpress
- MYSQL_USER=wordpress
- MYSQL_PASSWORD=wordpress
ports:
- port: 3306
- name: web
containers:
- image: wordpress:4
env:
- WORDPRESS_DB_HOST=database:3306
- WORDPRESS_DB_PASSWORD=wordpress
- WORDPRESS_DB_USER=wordpress
- WORDPRESS_DB_NAME=wordpress
ports:
- port: 80
type: external

Running opencompose tool
$ opencompose convert -f wordpress.yaml
created file "database-service.yaml"
created file "database-deployment.yaml"
created file "web-service.yaml"
created file "web-deployment.yaml"
$ kubectl create -f .

Kollaborating with Kubernetes community

Comparison of all three tools
Feature docker-compose Kompose OpenCompose
Define k8s service type - Using docker-compose
labels.
Define type under port
Kubernetes Jobs - Using docker-compose
restart
-
Secrets - - Define a secret
Volumes Cannot define size Creates a pvc of
100MB
Well defined data
structure for volumes
Liveness and
Readiness
- - Define health
Multiple containers in
one Pod
- - Define container list
under each service

References:
● Kompose http://kompose.io/
● OpenCompose https://github.com/redhat-developer/opencompose/

Meetup
● Upcoming meetup bit.ly/k8s101
● Meetup Page bit.ly/meetupk8s

Making kubernetes simple for developers

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