How can I keep my database, but change the code in docker-compose?

Question

I have a Python+MySQL webservice running on a Digital Ocean droplet in production. When I updated the code in the project on my local machine, I want the changes to take place in the droplet (in production) as well. So I do the following to deploy:

$ ssh root@12.34.56.78
# cd project
# git pull
# docker-compose down
# docker-compose build
# docker-compose up -d

After this, my database is empty. It has none of my tables in it. How can I update the code which is running, but not lose the data?

My Code

Project structure

.
├── db
├── docker-compose.yml
└── web
    ├── Dockerfile
    ├── project
    │   ├── app.py
    │   ├── __init__.py
    │   ├── blueprint1
    │   ├── blueprint2
    │   ├── models.py
    │   ├── static
    │   ├── templates
    │   └── _version.py
    ├── Makefile
    ├── migrations
    ├── README.md
    ├── setup.cfg
    ├── setup.py
    ├── start.sh
    ├── tests
    └── tox.ini

docker-compose.yml

version: "2"
services:
  db:
    image: mysql:5.7
    ports:
      - "32000:3306"
    environment:
      MYSQL_DATABASE: ***
      MYSQL_ROOT_PASSWORD: ***
    volumes:
      - ./db:/docker-entrypoint-initdb.d/:ro
  app:
    build: ./web
    links:
      - db
    ports:
      - "5000:5000"
    environment:
      MYSQL_PORT: 32000

Dockerfile

FROM python:3.7-slim

# Copy projects code
RUN apt-get update && apt-get install -y git
COPY . /opt/app
WORKDIR /opt/app
RUN pip install -e . --no-cache-dir

# Start app
ENV ENV=prod
EXPOSE 5000
ENTRYPOINT ["sh", "start.sh"]
CMD ["/opt/app/start.sh"]

What I've tried

# This killed my data:
$ docker-compose up -d --build app

# This did NOT update the code in app:
# 1
$ docker-compose stop app && docker-compose up -d app
# 2
$ docker-compose up -d --no-deps --build app

Answer 1

You have to create a named volume for your database like so

version: '3'

services:    
  mysql:
    image: mysql:5.7
    volumes:
      - mysql_data:/var/lib/mysql

volumes:
  mysql_data:

Now you can do safly run docker-compose stop or docker-compose down without losing your data on the mysql_data volume. Only when you run docker-compose down -v it will remove the volume as well.

You can see all your named volumes by running docker volume ls

Quick note: docker-compose is designed for development and not for production. You might want to consider a different strategy.

Answer 2

1. Create folder on host-machine

mkdir /data/mysql

2. Start your MySQL in docker
3. Copy database from running MySQL container in to host-machine

docker ps | grep mysql
docker cp <container_id>:/var/lib/mysql /data/mysql

4. Make change in your docker-compose.yml

    volumes:
      - ./db:/docker-entrypoint-initdb.d/:ro
      - /data/mysql:/var/lib/mysql

5. Restart all.

Answer 3

If you just want to update the app container without touching db container why not do

docker-compose down app
docker-compose up app

In this case you are just rebuilding your app container without touching db container.

And also its recommended to keep your containers stateless. Store your mysql data on local machine as Qteb suggests.

Thanks.

Answer 4

First, you need to have a named volume for data persistence as mentioned by Chris.

Then, build the code image and start the container from the new image individually:

docker-compose up -d --no-deps --build app

The --no-deps flag doesn't start any linked services. Linked services are started by default. That would destroy your data (like when you did docker-compose up -d --build app).

References:

• https://staxmanade.com/2016/09/how-to-update-a-single-running-docker-compose-container/
• https://docs.docker.com/compose/reference/up/

Answer 5

To store mysql database or other database data make sure your docker-compose.yml will look like 1.if you want to use Dockerfile

version: '3.1'

services:
  php:
    build:
      context: .
      dockerfile: Dockerfile
    ports:
      - 80:80
    volumes:
      - ./src:/var/www/html/
  db:
    image: mysql
    command: --default-authentication-plugin=mysql_native_password
    restart: always
    environment:
      MYSQL_ROOT_PASSWORD: example
    volumes:
      - mysql-data:/var/lib/mysql

  adminer:
    image: adminer
    restart: always
    ports:
      - 8080:8080
volumes:
  mysql-data:

2.if you want to use your image instead of Dockerfile than your docker-compose.yml will looks like

version: '3.1'   

services:
  php:
    image: php:7.4-apache
    ports:
      - 80:80
    volumes:
      - ./src:/var/www/html/
  db:
    image: mysql
    command: --default-authentication-plugin=mysql_native_password
    restart: always
    environment:
      MYSQL_ROOT_PASSWORD: example
    volumes:
      - mysql-data:/var/lib/mysql

  adminer:
    image: adminer
    restart: always
    ports:
      - 8080:8080
volumes:

if you want to store or preserve data of mysql then must remember to add two lines in your docker-compose.yml

volumes:
  - mysql-data:/var/lib/mysql

and

volumes:
  mysql-data:

after that use this command

docker-compose up -d

now your data will persistent and will not be deleted even after using this command

docker-compose down

extra:- but if you want to delete all data then you will use

docker-compose down -v

plus you can check your database data list by using this command

docker volume ls

DRIVER              VOLUME NAME
local               35c819179d883cf8a4355ae2ce391844fcaa534cb71dc9a3fd5c6a4ed862b0d4
local               133db2cc48919575fc35457d104cb126b1e7eb3792b8e69249c1cfd20826aac4
local               483d7b8fe09d9e96b483295c6e7e4a9d58443b2321e0862818159ba8cf0e1d39
local               725aa19ad0e864688788576c5f46e1f62dfc8cdf154f243d68fa186da04bc5ec
local               de265ce8fc271fc0ae49850650f9d3bf0492b6f58162698c26fce35694e6231c
local               phphelloworld_mysql-data