Getting Started with Docker and Kubernetes 101 More : https://blog.kubeify.com/2020/05/17/getting-started-with-docker-and-kubernetes-part-1/

1. Kubernetes 101
Tame your containers

2. Docker concepts
Container
● An extremely lightweight VM
holding code, libraries needed to
run apps
● Uses certain linux utilities to
provide isolation (namespaces,
cgroups)
● Fast start, hyper dense, and
portable
Image
A read-only template format
used to create docker containers
from a spec (Dockerfile)
Registry
Docker registry holds images,
just like S3.
Example: Dockerhub, AWS
ECR, GCP GCR, etc...
Dockerfile to Docker Image
> docker build -t demo .
Sending build context to Docker
daemon 365.6kB
Step 1/14 : FROM ruby:2.4-slim-jessie
---> aef69a49c1cd
...
> docker run alpine echo Hello World
Unable to find image 'alpine:latest' locally
latest: Pulling from library/alpine
Digest: sha256:769fddc7cc2f0a1c35abb2f91432e8beecf83916c421420e6a6da9f8975464b6
Status: Downloaded newer image for alpine:latest
Hello World

3. Docker CLI
docker --help
Usage: docker [OPTIONS] COMMAND
A self-sufficient runtime for containers
Commands:
build Build an image from a Dockerfile
cp Copy files/folders between a container and the local filesystem
exec Run a command in a running container
images List images
inspect Return low-level information on Docker objects
kill Kill one or more running containers
logs Fetch the logs of a container
pull Pull an image or a repository from a registry
push Push an image or a repository to a registry
restart Restart one or more containers
rm Remove one or more containers
rmi Remove one or more images
run Run a command in a new container
wait Block until one or more containers stop, then print their exit codes
Run 'docker COMMAND --help' for more information on a command.

4. Challenges with multiple containers
● How to scale?
● How to avoid port conflicts?
● How to manage them in multiple
hosts?
● What happens if a host has a trouble?
● How to keep them running?
● How to update them?
● Where are my containers?
- Configuration
- Scaling & Health
- Monitoring
- Scheduling
- Discovery
- Security

5. Meet kubernetes
Kubernetes is a an open source system for automating
containerized applications.
Manage applications, not machines
● Very Powerful and huge community
● Manages containers at scale
● Run everywhere (supports multiple cloud and bare-metal environments)
● Self healing
● Get more out of hardware
● Platform for Platform (distributed systems)

6. What can it do ?
● Start 5 containers using image
demo/api:v1
● Place an internal load balancer in front
of those containers
● Start 10 containers using image
demo/web:v1
● Place a public load balancer in front of
those containers
● If traffic spikes, grow those out cluster
and add containers
● New release! replace my container with
new version demo/web:v2
● Basic Auto-Scaling/Monitoring
● Long running processes ( Job,
Cronjobs)
● Stateful services (databases, caches)
● Resources & Capacity planning
● Storing configurations/secrets
● etc ...

7. Architecture -Cluster
The cluster is made of two types of
Nodes - Master and Worker
K8S Control plane (api, etcd,
scheduler) runs on master nodes,
which manages entire thing
Your apps run on worker nodes

8. Interacting with Cluster
Kubectl - a rich CLI to talk to
Kubernetes API
> alias kc = kubectl
kc get nodes
kc get nodes -o yaml
kc edit node ip-xx-xx
> kubectl get nodes
NAME STATUS ROLES AGE VERSION
ip-172-20-107-197.ec2.internal Ready node 170d v1.10.11
ip-172-20-107-51.ec2.internal Ready master 170d v1.10.11
ip-172-20-114-41.ec2.internal Ready node 170d v1.10.11
ip-172-20-52-179.ec2.internal Ready node 64d v1.10.11
ip-172-20-60-229.ec2.internal Ready master 170d v1.10.11
ip-172-20-69-22.ec2.internal Ready node 170d v1.10.11
ip-172-20-86-122.ec2.internal Ready master 170d v1.10.11

9. Pod
Small group of tightly coupled containers
The smallest deployed object
Shared namespace (IP, disk)
Not durable and ephemeral in nature
example: data-puller and web-service

10. Deployment
Represent an application deployment
and controls number of pods. It
handles:
● Scaling
● Updating software versions
● Rolling updates
● Pod health checking and healing
● Rollback
apiVersion: apps/v1
kind: Deployment
metadata:
name: nginx-deployment
labels:
app: nginx
spec:
replicas: 3
selector:
matchLabels:
app: nginx
template:
metadata:
labels:
app: nginx
spec:
containers:
- name: nginx
image: nginx:1.7.9
ports:
- containerPort: 80

11. Services
● Acts as a load-balancer for pods
● Persistent endpoint
● exposes the pods (internal and external)
● Service is associate with pod through label
selector
- ClusterIP – exposed on cluster-internal IP
- NodePort – exposed on nodes IP .via static port
- LoadBalancer – exposed externally on providers NLB
- ExternalName – map service to DNS name
apiVersion: v1
kind: Service
metadata:
name: my-service
spec:
selector:
app: my-app
ports:
- name: http
protocol: TCP
port: 80
targetPort: 9376
- name: https
protocol: TCP
port: 443
targetPort: 9377

12. YAML Manifests
YAML file to declare desired state of
Kubernetes object types
● Define Kubernetes type
● Define type specification
● Labels / Annotations
● Metadata
Use kubectl to apply them against
cluster
apiVersion: apps/v1
kind: Deployment
metadata:
name: nginx-deployment
annotations:
app/instance: “nginx”
labels:
app: nginx
spec:
replicas: 3
selector:
matchLabels:
app: nginx

13. Advance Objects
ConfigMap, Secrets
Volume, PersistentVolume, PVC
DaemonSets, StatefulSets
Jobs, CronJobs
Third Party extensions (CRD)

14. Demo (101)
Shipping images to registry
Running application on Kubernetes
Scaling out demo app
Rolling upgrades

15. Demo (advance)
Here is the source code - Github
DockerCoins is made of 5 services:
- rng = web service generating random bytes
- hasher = web service computing hash of POSTed data
- worker = background process calling rng and hasher
- webui = web interface to watch progress
- redis = data store (holds a counter updated by worker)

16. Deploy
● Deploy Redis
kubectl create deployment redis --image=redis
● Deploy everything else
for SERVICE in hasher rng webui worker; do
kubectl create deployment $SERVICE --image=$REGISTRY/$SERVICE:$TAG
Done
● Expose deployments
kubectl expose deployment redis --port 6379
kubectl expose deployment rng --port 80
kubectl expose deployment hasher --port 80
kubectl expose deploy/webui --type=NodePort --port=80

17. We are always available to talk about your
challenges moving forward towards
microservices and containers.
Dinesh Yadav (dinesh@razorops.com)
https://razorops.com