Deploy dJango code

Use Kubernetes to deploy docker for load balance

Step 1: Prepare machine for Kubernetes 

$ brew cask install minikube
$ brew install kubectl
$ minikube start
$ minikube status

Utilize the docker daemon within minikube
normally you build docker image, then push to Kubernetes but When using a single VM of Kubernetes, it’s really handy to reuse the Minikube’s built-in Docker daemon; as this means you don’t have to build a docker registry on your host machine and push the image into it - you can just build inside the same docker daemon as minikube which speeds up local experiments. Just make sure you tag your Docker image with something other than ‘latest’ and use that tag while you pull the image.

$ eval $(minikube docker-env)
$ kubectl config current-context

$ minikube dashboard

Step 2: Prepare Dockers

we need to define 4 dockers
1) Nginx: will serve static files
2) Django/Gunicorn : Gunicorn will serve python files
3) DB: mysql
4) Solr 



2.1) Select Docker Base image 
The python images come in many flavors, each designed for a specific use case.

2.1.a) python:<version> : It has a large number of extremely common Debian packages. This reduces the number of packages that images that derive from it need to install.

2.1.b) python:<version>-slim: only contains the minimal packages needed to run python

2.1.c) python:<version>-alpine: image based on Alpine images [size is ~5MB], Alpine use musl libc instead of glibc. so certain software might run into issues depending on the depth of their libc requirements. However, most software doesn't have an issue with this


2.2) Gunicorn configuration

Gunicorn should only need 4-12 worker processes to handle hundreds or thousands of requests per second. Generally we recommend (2 x $num_cores) + 1 as the number of workers to start off with. 

2.3) NGINX Configurationa)
2.3.a) worker_processes – The number of NGINX worker processes (the default is 1). In most cases, running one worker process per CPU core works well, and we recommend setting this directive to auto to achieve that. There are times when you may want to increase this number, such as when the worker processes have to do a lot of disk I/O.

Get number of cores available

grep processor /proc/cpuinfo | wc -l




2.3.b) worker_connections – The maximum number of connections that each worker process can handle simultaneously. The default is 512, but most systems have enough resources to support a larger number. The appropriate setting depends on the size of the server and the nature of the traffic, and can be discovered through testing.
Get connections that can simultaneously be served using the next command

ulimit -n




=======================

Prepare Dockers:
a) Prepare Django Docker

Create folder with name "django-docker" (mkdir django-docker) contains file "Dockerfile" (touch Dockerfile), and requirements.txt

Dockerfile File contents:

FROM python:3.6.7-alpine
ENV PYTHONUNBUFFERED 1
RUN mkdir /code
WORKDIR /code
ADD requirements.txt /code/
RUN pip install -r requirements.txt
ADD ./ /code/
CMD ["python", "mysite/manage.py", "runserver", "0.0.0.0:8001"]

requirements.txt File contents:

beautifulsoup4==4.7.1
bs4==0.0.1
certifi==2019.3.9
chardet==3.0.4
Django==2.1.7
gunicorn==19.9.0
djangorestframework==3.9.2
html5lib==1.0.1
idna==2.8
lxml==4.3.2
numpy==1.16.2
pandas==0.24.2
Pillow==5.4.1
pymarc==3.1.12
PyMySQL==0.9.3
pysolr==3.8.1
python-dateutil==2.8.0
pytz==2018.9
requests==2.21.0
six==1.12.0
soupsieve==1.8
urllib3==1.24.1
webencodings==0.5.1

Build docker
$ docker build -t django-docker:0.0.1 .

Run docker and expose port 8001
$ docker run -p 8001:8001 docker-django:0.0.1

Now user can view the django project by visit  http://localhost:8001

================================


Automate build process using docker compose

1) Create a ymal file (touch docker-compose.yml)

File contents:

version: '3'

services:
  web:
    build: ./django-docker/
    command: python mysite/manage.py runserver 8001
    ports:
      - "8001:8001"

2) Remove CMD from ./django-docker/Dockerfile because ymal file do that now.

3) Build then Run the Docker

$ docker-compose build
$ docker-compose up -d

3.1) When you have two yaml files, you can choose the yaml for build and up
$ docker-compose -f production.yml up -d

3.2) List current active containers
$ docker-compose ps

3.3) To see which environment variables are available to the web service, run:
$ docker-compose run web env

3.4) To view the logs:
$ docker-compose logs

3.5) to stop docker
$ docker-compose down

4) to run bash commands against docker

$ docker-compose exec web bash 

Common Django tasks:
$ docker-compose exec web python mysite/manage.py migrate
$ docker-compose exec web python mysite/manage.py createsuperuser

Note:
Docker content should be readonly and if we have a dynamic data we can map docker folder to a container folder to keep changes.

ie, in yaml file map /TargetDir directory to container /ContainerDir directory

volumes:
  - /TargetDir : /ContainerDir

b) Create DB docker

update ymal file and connect to web docker

db:
    image: mysql:5.7
    restart: always
    environment:
      MYSQL_DATABASE: 'db'
      MYSQL_USER: 'user'
      MYSQL_PASSWORD: 'password'
      MYSQL_ROOT_PASSWORD: 'password'
    ports:
      - '3306:3306'
    expose:
      - '3306'
    volumes:
      - my-db:/var/lib/mysql
    networks:
      - backend

networks:
  backend:
    driver: bridge

the ymal file contains passwords and it is better to keep out side ymal file, .env is the best  place

create .env file in the same yaml directory

MYSQL_DATABASE =ddl
MYSQL_USER=user1
MYSQL_PASSWORD =root
MYSQL_ROOT_PASSWORD =root
DB_SERVICE=DB

use ${Variable Name} to read any value from .env file inside yaml file

So, the ymal file can be

db:
    image: mysql:5.7
    restart: always
    environment:
      MYSQL_DATABASE: ${MYSQL_DATABASE}
      MYSQL_USER: ${MYSQL_USER}
      MYSQL_PASSWORD: ${MYSQL_PASSWORD}
      MYSQL_ROOT_PASSWORD: ${MYSQL_ROOT_PASSWORD}
    ports:
      - '3306:3306'
    expose:
      - '3306'
    volumes:
      - my-db:/var/lib/mysql
    networks:
      - backend

networks:
  backend:
    driver: bridge

c) Create nginx load balancer docker

Create folder with name "nginx" (mkdir nginx) contains file "Dockerfile" (touch Dockerfile)

Dockerfile contents

FROM nginx:latest
RUN rm /etc/nginx/sites-enabled/default
COPY default    /etc/nginx/sites-enabled/default

default file contents

server {

    listen 80;
    server_name localhost;
    charset utf-8;

    location /static {
        alias /usr/src/app/static;
    }

    location / {
        proxy_pass http://web:8000;
        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    }

}

The Final ymal file
yaml file that configure django, DB,  and nginx will look like

version: "3"

services:

  web:
    restart: always
    build: ./django-docker/
    expose:
      - "8000"
    ports:
      - "8000:8000"
    depends_on:
      - db
    networks:
      - backend
    volumes:
      - web-django:/usr/src/app
      - web-static:/usr/src/app/static
    env_file: .env
    environment:
      DEBUG: 'true'
    command: /usr/local/bin/gunicorn ddlDjango.wsgi:application -w 2 -b :8000



  db:
    image: mysql:5.7
    restart: always
    environment:
      MYSQL_DATABASE: 'db'
      MYSQL_USER: 'user'
      MYSQL_PASSWORD: 'password'
      MYSQL_ROOT_PASSWORD: 'password'
    ports:
      - '3306:3306'
    expose:
      - '3306'
    volumes:
      - my-db:/var/lib/mysql
    networks:
      - backend


  nginx:
    restart: always
    build: ./nginx/
    ports:
      - "80:80"
    volumes:
      - web-static:/www/static
    networks:
      - backend

networks:
  backend:
    driver: bridge

Notes:
1) network: When containers are placed in the same network, they are reachable by each other using their container name and other alias as host.

2) depends_on: expresses start order (and implicitly image pulling order)

3) ports: maps container port to the host.

4) EXPOSE: opens the port in the container, making it accessible by other containers. but not accessible to the host (does not actually publish the port)

5) env_file: .env  read the contents of .env file and send to docker as an environmental variable

6) environment: send the given key/values pairs to docker as an environmental variable

    and you can read these values later inside settings.py using os.environ.get (Key, DefaultValue)

setting.py dynamic line example :

import os
SECRET_KEY = os.environ.get('SECRET_KEY','sdfgtw54sdgsdfgsdfgsdfgsfd')

==========

Kubernetes based on dockers

To Deploy docker on Kubernetes, we need to convert existing Docker Compose yaml files into the necessary Kubernetes configuration.
which means created a Kubernetes deployment and a Kubernetes service for every container that had an exposed port.

Kubernetes commands

Create new pod based on nginx version 1.10.0 image
$ kubectl run nginx --image=nginx:1.10.0

List available pods 
$ kubectl get pods

Create service to allow connecting to the existing pod listen to port 80
$ kubectl expose deployments nginx --port 80 --type loadBalancer

List available services
$ kubectl get services

Create pods based on ymal file
$ kubectl create   -f    pods/monolith.yaml

Working with one POD

List available pods to get pod name
$ kubectl get pods

Get Pod details 
$ kubectl describe pods <<Pod Name>>


Forward traffic from a given host port to pod port
$ kubectl port-forward <<Pod Name>>  <<Host Port >> : <<Pod Port >>


View Pod Logs
$ kubectl logs <<Pod Name>>


View Pod Logs stream in realtime
$ kubectl logs -f  <<Pod Name>>

Login to shell inside a Pod

$ kubectl exec <<Pod Name >>   --stdin    --tty   -c <<Pod Name >> /bin/sh


To logout from Pod SSH 
$ exit




==============================================




Working with group of PODs (using Services)

Sample service yaml configuration file

Notes: we select the pods that will affected by this service using "selector" section


Create Service based on yaml file 
$ kubectl create -f services/monolith.yaml


Select Pods based on selection criteria (pods that has some labels) 
$ kubectl get pods -l "app=monolith, secure=enabled"


Add label to exist pod
$ kubectl label pods << Pod Name >>  "Lable1 = Value1"


References

List of available commands
https://kubernetes.io/docs/reference/generated/kubectl/kubectl-commands

how to do individual tasks step by step 
https://kubernetes.io/docs/tasks/