ContainerDayVietnam2016: Django Development with Docker

Django Development with Docker
Cuong Tran - Docker Hanoi

About me
Cuong Tran
Community: Docker Hanoi Organizer
Job: Developer at Higgs Valley
Email: tranhuucuong91@gmail.com
Github: https://github.com/tranhuucuong91
Blog: http://tranhuucuong91.github.io/
Domain: Machine Learning, DevOps, Cloud
2

Agenda
1. Introduction Django Stack
2. Run Django Stack
3. Common activity
4. Problems and solutions (P&S)
5. Snippets
6. Q&A
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1. Introduction Django Stack
4
Nginx
Django
PostgresRedis

1. Introduction Django Stack: Project Structure
├── docker-compose.yml
├── docker-env
├── nginx
│ ├── Dockerfile
│ └── sites-enabled
│ └── django_project
├── production.yml
├── README.md
└── web
├── docker_django
│ ├── apps
│ ├── __init__.py
│ ├── settings.py
│ ├── urls.py
│ └── wsgi.py
├── Dockerfile
├── manage.py
├── requirements.txt
└── static
├── images
│ └── django-pony.png
└── main.css
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1. Introduction Django Stack: docker-compose.yml
version: "2"
services:
nginx:
#restart: always
build: ./nginx/
ports:
- "80:80"
volumes:
- /www/static
volumes_from:
- web
depends_on:
- web
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web:
#restart: always
build: ./web
expose:
- "8000"
depends_on:
- postgres
- redis
volumes:
- ./web:/usr/src/app
- ./web/static:/usr/src/app/static
env_file: docker-env
environment:
DEBUG: 'true'
command: /usr/local/bin/gunicorn
docker_django.wsgi:application -w 2 -b :8000
--access-logfile /var/log/gunicorn.log

1. Introduction Django Stack: docker-compose.yml
postgres:
#restart: always
image: postgres:9.5
ports:
- "5432:5432"
volumes:
- pgdata:/var/lib/postgresql/data/
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redis:
#restart: always
image: redis:3.2
ports:
- "6379:6379"
volumes:
- redisdata:/data
volumes:
pgdata:
redisdata:

2. Run Django Stack
# build stack
docker-compose build
# up stack
docker-compose up -d
# migrate data
docker-compose run --rm web /usr/local/bin/python manage.py
migrate
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3. Common Activity: Run container
● View web
● Run command in container
● Show logs
● Connect database to container
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3. Common Activity: Update git
● Edit and git commit
● Git ignore files for dev, test, prod environments
● Update git
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3. Common Activity: Build container
● Rebuild docker images
● Push to private registry
● Update docker images in production
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4. P&S: Handle `docker stop`
● When call docker stop, docker will send SIGTERM to main process
inside the container. And after a grace period (default 10s), docker will
send SIGKILL.
12Image Source: http://www.slideshare.net/LeszekGodlewski/advanced-linux-game-programming

4. P&S: Handle `docker stop`
● The main process need to handle the signal and graceful stop.
import sys, signal, time
def handler(signum = None, frame = None):
print('Signal handler called with signal', signum)
time.sleep(1) #here check if process is done
print('Wait done')
sys.exit(0)
for sig in [signal.SIGTERM, signal.SIGINT, signal.SIGHUP, signal.SIGQUIT]:
signal.signal(sig, handler)
while True:
time.sleep(6)
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4. P&S: Startup order
Issue: Docker Compose:
● Will not wait until a container is "ready".
● Only until it’s running.
Solution:
● Use a tool such as wait-for-it or dockerize.
● (Or) Write your own wrapper script to perform a more application-specific
health check.
14Reference: https://docs.docker.com/compose/startup-order/

4. P&S: Startup order
wait-for-postgres.sh
#!/usr/bin/env bash
set -e
host="$1"
shift
cmd="$@"
until psql -h "$host" -U "postgres" -c 'l'; do
>&2 echo "Postgres is unavailable - sleeping"
sleep 1
done
>&2 echo "Postgres is up - executing command"
exec $cmd
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wait-for-it.sh
#!/usr/bin/env bash
# Use this script to test if a given TCP
host/port are available
cmdname=$(basename $0)
echoerr() { if [[ $QUIET -ne 1 ]]; then echo "$@"
1>&2; fi }
usage()
{
cat << USAGE >&2
Usage:
$cmdname host:port [-s] [-t timeout] [--
command args]
-h HOST | --host=HOST Host or IP under
test
-p PORT | --port=PORT TCP port under
test
...

4. P&S: Speed up `docker build`
Use .dockerignore
● Because docker will put current directory in build context.
● To increase the build's performance, you can exclude files and directories
by adding a .dockerignore file.
● Syntax like .gitignore.
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4. P&S: Speed up `docker build`
Build cache
● The orders of command -> image layers -> build speed & image size &
storage capacity
1. Install fixed things before. Ex: library, runtime
2. Install changed things after. Ex: code
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4. P&S: Limit Resources
cpu_shares: 73
cpu_quota: 50000
cpuset: 0,1
mem_limit: 1000000000
memswap_limit: 2000000000
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5. Snippets
#--- Docker stats ---
# stats all service in docker compose directory
docker stats `docker-compose ps | tail -n+3|awk '{print $1}'`
# stats all docker container are running
docker stats `docker ps | awk '{print $NF}' | tail -n+2`
#--- Docker remove ---
# remove all stopped containers
docker ps -a | awk '/Exit/ {print $1}' | xargs -r docker rm
# remove all untagged images
docker images | awk '/^<none>/ {print $3}' | xargs -r docker rmi
# remove old version images
docker images | grep ro.lan:5001/tranhuucuong91/nginx | tail -n +4 | awk '{print $3}' | xargs -r docker rmi
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5. Snippets (cont.)
Save all the images on docker-compose.yml and deploy on machine not
connected to the internet
# Save Compressed Images
IMAGES=`grep '^s*image' docker-compose.yml | sed 's/image://' | sort | uniq`
docker save $IMAGES | gzip > images.tar.gz
# Load Compressed Images
gunzip -c images.tar.gz | docker load
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[1] https://github.com/tranhuucuong91/docker-training
[2] https://realpython.com/blog/python/django-development-with-docker-co
mpose-and-machine/
[3] https://github.com/pydanny/cookiecutter-django
[4] https://docs.docker.com/engine/reference/builder/
[5] https://docs.docker.com/compose/compose-file
References
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