Docker & Kubernetes 101

Published at Dec 20, 2018 better viewed as a slideshow

#containers

Docker

Docker is a tool designed to make it easier to create, deploy, and run applications by using containers. Containers allow a developer to package up an application with all of the parts it needs, such as libraries and other dependencies, and ship it all out as one package. — OpenSource.com, What is Docker?

Infrastructure

Don’t worry about the system your application will ultimately run on.

Install Docker

Install at Docker’s getting-started

Setup Docker

First, ensure you are using an up-to-date docker engine. In the terminal,

Run docker info and check for any errors
Run docker --version and ensure you have version >=17.06

Setup Docker Resources

Ensure you have set enough resources for Docker to run smoothly: In the taskbar, click the whale icon → Preferences → Advanced

(I set 6 CPUs and 8GB RAM for Docker)

Settings

World Smallest Image

Every single Docker container begins as a pure vanilla Linux machine that knows nothing.

Where It All Begins

A Docker image consists of read-only layers each of which represents a Dockerfile instruction. The layers are stacked and each one is a delta of the changes from the previous layer.

Images start as a fresh, isolated machine and the very same dependencies get added to it. Every. Single. Time.

dockerfile

FROM scratch

ADD hello /

CMD ["/hello"]

Build your First Image

bash

docker build -t tiny-hello-world .
docker images

Run your First Container

bash

docker run tiny-hello-world
docker ps -a

Clean After Yourself

Delete a container:

bash

docker rm condescending_ptolemy

Next time, run container & delete after exit:

bash

docker run --rm tiny-hello-world

Advanced

Delete all stopped containers:

bash

docker container prune

Delete all dangling images:

bash

docker image prune

My First Containerized Node Application

I recommend Dockerfile documentation. It’s very well written.

Dockerfile

Node service:

Dockerfile

## creates a layer from the node:carbon Docker image
FROM node:8.14-alpine

## create the app directory for inside the Docker image
WORKDIR /usr/src/app

## copy and install app dependencies from the package.json (and the package-lock.json) into the root of the directory created above
COPY package*.json ./
RUN yarn install

## bundle app source inside Docker image
COPY . .

## expose port 8080 to have it mapped by Docker daemon
EXPOSE 3000

## define the command to run the app
CMD [ "yarn", "run", "start" ]

app.js

javascript

var express = require('express');
var app = express();

process.on('SIGINT', function () {
  process.exit();
});

app.get('/', function (req, res) {
  res.send("Hello World!
");
});

app.listen(3000, function () {
  console.log('Example app listening on port 3000!');
});

package.json

json

{
  "name": "docker-101-scene-02",
  "version": "1.0.0",
  "main": "index.js",
  "author": "Rafael Bodill",
  "license": "MIT",
  "scripts": {
    "start": "node app.js"
  },
  "dependencies": {
    "express": "^4.16.4"
  }
}

Let’s Build & Run

bash

docker build -t test-node .
docker run -it --rm test-node

On a new terminal:

bash

curl localhost:3000

Where’s my service? :(

Expose Ports to Host

bash

docker run -it --rm -p 3000:3000 test-node

On a new terminal:

bash

curl localhost:3000

Hooray!

Let’s Add a Route

Append to app.js:

javascript

app.get('/healthz', function (req, res) { res.send('OK') })

Rebuild image:

bash

docker build -t test-node .
docker run -it --rm test-node

Docker Layer Caching

Docker Layers

bash

$ docker history test-node

IMAGE               CREATED          SIZE      CREATED BY
d17562ebd02e        27 minutes ago   0B        CMD ["yarn" "start"]
c24c2a8c7a2a        27 minutes ago   0B        EXPOSE 3000
001439668f54        27 minutes ago   1.78MB    COPY dir:0dc6500de44402cb2…
24e151c2462b        27 minutes ago   7.13MB    yarn install
9dd639668f68        27 minutes ago   226B      COPY file:b365e33dfa656564…
a93bcafb8a76        27 minutes ago   0B        WORKDIR /usr/src/app

.. Wait .. Our app.js is 1.78MB?

Ignoring Files

Create a .dockerignore file with:

txt

.git
.dockerignore
*.md
*.png
Dockerfile
node_modules

Rebuild image:

bash

docker build -t test-node .
docker history test-node

Now it’s better.

Linux Containers

Images vs. Containers

Docker images are executable packages that include everything needed to run an application — the code, a runtime, libraries, environment variables, etc.

Docker containers are a runtime instance of an image — what the image becomes in memory when executed.

Examples of Docker containers. Each one comes from a specific Docker image.

Entering Container’s Shell

bash

docker run -d --name bob -p 3000:3000 test-node
docker exec -it bob sh

You are now INSIDE the ~~matrix~~ container!

bash

> netstat -ntulp
> wget -q -O- localhost:3000
> top
> free -m
> exit

Running Different Commands

bash

docker run --rm -it test-node sh
docker run --rm -it test-node ls -alp

View Container Information

bash

docker inspect bob | less
docker logs -f bob
docker stats bob

Manage State

bash

docker stop bob
docker start bob
docker restart bob
docker rm -f bob

Private Services

bash

docker run --rm -p 3000:3000 artifactory.local/myapp

Oh oh. What’s missing here?

Mount Volumes

Let’s mount our configuration from a different Git repository:

bash

git clone git@git.local:mycompany/myconfig.git

docker run --rm -v $PWD/myconfig:/etc/myapp 
  -p 3000:3000 artifactory.local/myapp

Dog-gone it. What else are we missing?

Environment Variables

Oh. Our environment variable! It tells the configuration where to read from:

bash

docker run --name bob -v $PWD/myconfig:/etc/myapp 
  -e MYAPP_CFG_ROOT=/etc/myapp -p 3000:3000 
  artifactory.local/myapp

Viewing Logs

In a different terminal,

bash

docker logs -f bob
docker exec -it bob tail -f /var/log/myapp/api.log

Simplifying Workspaces

Docker Compose offers a number of benefits over the Docker CLI in all stages of development.

Essentially, what Docker Compose is, is a recipe card — it’s a recipe of services that make up an application and the docker-compose.yml dictates how the services are mixed together.

Simple Example

Let’s inspect our docker-compose.yml file:

yaml

version: "2"
services:

  myapp:
    image: artifactory.local/myapp
    environment:
      MYAPP_CFG_ROOT: /etc/myapp
    ports:
      - "3000:3000"
    volumes:
      - ./myconfig:/etc/myapp

Running Your Composition

bash

git clone git@git.local:mycompany/myconfig.git
docker-compose up

On a different terminal:

bash

curl localhost:3000

Let’s Add (3rd)Parties!

yaml

version: "2"
services:

  myapp:
    image: artifactory.local/myapp
    environment:
      MYAPP_CFG_ROOT: /etc/myapp
    ports:
      - "3000:3000"
    volumes:
      - ./myconfig:/etc/myapp

  redis:
    image: "redis:alpine"

Let’s run it:

bash

docker-compose up

Whoa!

Give me morrrre!

yaml

version: "2"
services:

  myapp:
    image: artifactory.local/myapp
    environment:
      MYAPP_CFG_ROOT: /etc/myapp
    ports:
      - "3000:3000"
    volumes:
      - ./myconfig:/etc/myapp

  redis:
    image: "redis:alpine"

  mysql:
    image: "mysql:5.7"
    environment:
      MYSQL_ROOT_PASSWORD: root

Let’s run it:

bash

docker-compose up

Access Services

bash

## Access MySQL:
docker exec -it scene-05_mysql_1 mysql -u root -p

## Access Redis:
docker exec -it scene-05_redis_1 redis-cli GET /

Kubernetes (K8S) 101

https://docs.google.com/presentation/d/1BhUfwkiRTQZsvN9kCpxpbT09kpWFTiuAprOfGemrf6Q

Workstation Setup

bash

brew uninstall --force bash-completion
brew install kubernetes-cli kubectx fzf stern bash-completion@2

Append to your ~/.bash_profile for awesome shell completion:

bash

if [ -f /usr/local/share/bash-completion/bash_completion ]; then
  . /usr/local/share/bash-completion/bash_completion
fi

Setup kubectl Context

Cluster + User = Context

bash

## Integration
kubectl config set-cluster foobar-int-developer --server=https://1.2.3.4:6443 --certificate-authority=$HOME/.kube/int/ca.pem
kubectl config set-credentials int-developer --client-certificate=$HOME/.kube/int/developer.crt --client-key=$HOME/.kube/int/developer.key
kubectl config set-context foobar-int-developer --cluster=foobar-int-developer --user=int-developer

## Staging
kubectl config set-cluster foobar-stg-developer --server=https://5.6.7.8:6443 --certificate-authority=$HOME/.kube/stg/ca.pem
kubectl config set-credentials stg-developer --client-certificate=$HOME/.kube/stg/developer.crt --client-key=$HOME/.kube/stg/developer.key
kubectl config set-context foobar-stg-developer --cluster=foobar-stg-developer --user=stg-developer

kctx

bash

kubectl config use-context foobar-int-developer
kctx
kctx foobar-int-developer
kctx foobar-stg-developer

kubectl Cheat-sheet

bash

kubectl get namespaces
kubectl get deploy
kubectl get -n ingress-nginx deploy
kubectl get -n kube-system deploy
kubectl get --all-namespaces deploy
kubectl get pods -w
kubectl get pods -o wide
kubectl get events

kubectl get pods,svc,deploy
kubectl describe deploy push-service
kubectl top node
kubectl top pods
kubectl logs -f deploy/trips
kubectl logs -f deploy/trips -c trips
kubectl logs --previous trips-7d7f649996-nz876
kubectl exec -it trips-6c6887547d-lhbsb -- tail -f /var/log/myapp/api.log

Examining Deployed Objects

bash

kubectl get deploy
kubectl get pod
kubectl get svc
kubectl get deploy,pod,svc | grep myapp
kubectl get all | grep myapp

Describe Deployment

bash

kubectl describe deploy myapp
kubectl describe pod myapp-649887b547-fh7vw
kubectl top pod | grep myapp

Analyze Logs

bash

kubectl logs -f myapp-649887b547-fh7vw
kubectl exec -it myapp-649887b547-fh7vw -- tail -f /var/log/myapp/api.log

Jump into Container

bash

$ kubectl exec -it myapp-649887b547-fh7vw sh
> top
> free -h
> exit

Docker & Kubernetes 101

Docker

Infrastructure

Install Docker

Setup Docker

Setup Docker Resources

Settings

World Smallest Image

Where It All Begins

Build your First Image

Run your First Container

Clean After Yourself

Advanced

My First Containerized Node Application

Dockerfile

app.js

package.json

Let’s Build & Run

Expose Ports to Host

Let’s Add a Route

Docker Layer Caching

Docker Layers

Ignoring Files

Linux Containers

Images vs. Containers

Entering Container’s Shell

Running Different Commands

View Container Information

Manage State

Private Services

Mount Volumes

Environment Variables

Viewing Logs

Simplifying Workspaces

Simple Example

Running Your Composition

Let’s Add (3rd)Parties!

Give me morrrre!

Access Services

More on Docker-Compose

Kubernetes (K8S) 101

Workstation Setup

Setup kubectl Context

kctx

kubectl Cheat-sheet

Examining Deployed Objects

Describe Deployment

Analyze Logs

Jump into Container

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