dockerized python app

README.md

Dockerized simple python app

An example app for having python code dockerized connected to one service. In this proof of concept we connect to postgresql database, using the dataset library.

getting the code up

You just have to bring the containers up with compose:

docker-compose up

debugging

If you want to check tables after launch you can access a postgresql shell like explained in testing.sh

Accessing a python shell instead would require you to:

docker-compose exec app ash

$ ipython

notes

1. You can force the python container to do nothing by changing the command option inside the docker-compose.yml file.
2. You can play with dataset by using the previous step and opening ipython.

clean everything after testing

docker-compose down -v

docker-compose.yml

version: "3"
networks:
  dbnet:

services:

  app:
    build: pyalpine
    ##################
    # DIRECTLY EXECUTE THE CODE
    command: myapp
    # # DEBUGGING
    # command: sleep 1234567890
    ##################
    volumes:
      - ./testing.py:/usr/bin/myapp
    depends_on:
      - db
    networks:
      - dbnet

  db:
    image: postgres:9.6
    hostname: db
    environment:
      POSTGRES_USER: user
      POSTGRES_PASSWORD: pass
      POSTGRES_DB: mydatabase
    networks:
      - dbnet

Dockerfile

FROM alpine:3.6

RUN apk update && apk add \
    gcc \
    # there is a 'limit.h' missing in alpine when compiling psycopg2:
    # https://stackoverflow.com/a/30873179
    # linux-headers \
    musl-dev \
    # other dev packages necessary are:
    postgresql-dev python3-dev
RUN pip3 install --upgrade \
    pip \
    ipython psycopg2 dataset


ENV SLEEP_TIME 1234567890
CMD ['sleep', '$SLEEP_TIME']

testing.py

#! /usr/bin/env python3

# Access container:
# $ docker-compose exec app ash
# / # ipython

import time
import dataset

connected = False

while not connected:
    try:
        db = dataset.connect('postgresql://user:pass@db/mydatabase')
    except BaseException:
        print("Waiting for connection...")
        time.sleep(3)
    else:
        connected = True

tablename = 'testingconnection'
table = db[tablename]
table

table.insert(dict(name='John Doe', age=46, country='China'))
# db.commit()

users = db[tablename].all()
print(users)    # <-- iterator
list(users)     # <-- unpacked table content

print("Completed! Now sleeping...")
time.sleep(987654321)

testing.sh

docker-compose exec db bash

root@db:/# psql -U user -d mydatabase

mydatabase=# \d
--------+--------------------------+----------+-------
 public | testingconnection        | table    | user
 public | testingconnection_id_seq | sequence | user

mydatabase=# SELECT * FROM testingconnection;
 id |   name   | age | country
----+----------+-----+---------
  1 | John Doe |  46 | China
(1 row)