如何在docker-compose中缓存构建环境

Question

I am new to using docker-compose so I am not sure if I am using the correct approach to building changes in code. The docker-compose tutorial said that in order to update any changes in code, just make changes and refresh the link and the output will be refreshed(after code gets built by itself). That isn't happening for me. I have to stop the running docker-compose and then run the command docker-compose up --build which builds the system again. Now, my problem is that it downloads all the requirements in the python project. Currently the libraries aren't that many but they will increase at which point it will be extremely time consuming to download everything again and again. What should I do to avoid doing this when I only make changes to code and not the requirements.txt file.

Here is an example of my setup:
docker-compose.yml

version: '2'
services:
  web:
    build: .
    ports:
      - "5000:5000"
    env_file: .env
    depends_on:
      - db
    volumes:
      - ./webapp:/opt/webapp

  db:
    image: postgres:latest
    ports:
      - "5432:5432"

  redis:
    image: redis:alpine
    ports:
      - "6379:6379"

Dockerfile:

FROM python:3.4-alpine
ADD . /code
WORKDIR /code
RUN pip install -r requirements.txt
CMD ["python", "app.py"]

For every change I make in code and test it, I have to go through all these steps:

Building web
Step 1/5 : FROM python:3.4-alpine
 ---> 765c483d587c
Step 2/5 : ADD . /code
 ---> ce6f587fe477
Removing intermediate container bceef7c06a89
Step 3/5 : WORKDIR /code
 ---> cd3f4951f718
Removing intermediate container 5022780e47eb
Step 4/5 : RUN pip install -r requirements.txt
 ---> Running in 2dfe61c2537e
Collecting flask (from -r requirements.txt (line 1))
  Downloading Flask-0.12-py2.py3-none-any.whl (82kB)
Collecting redis (from -r requirements.txt (line 2))
  Downloading redis-2.10.5-py2.py3-none-any.whl (60kB)
Collecting itsdangerous>=0.21 (from flask->-r requirements.txt (line 1))
  Downloading itsdangerous-0.24.tar.gz (46kB)
Collecting click>=2.0 (from flask->-r requirements.txt (line 1))
  Downloading click-6.7-py2.py3-none-any.whl (71kB)
Collecting Werkzeug>=0.7 (from flask->-r requirements.txt (line 1))
  Downloading Werkzeug-0.11.15-py2.py3-none-any.whl (307kB)
Collecting Jinja2>=2.4 (from flask->-r requirements.txt (line 1))
  Downloading Jinja2-2.9.5-py2.py3-none-any.whl (340kB)
Collecting MarkupSafe>=0.23 (from Jinja2>=2.4->flask->-r requirements.txt (line 1))
  Downloading MarkupSafe-0.23.tar.gz
Installing collected packages: itsdangerous, click, Werkzeug, MarkupSafe, Jinja2, flask, redis
  Running setup.py install for itsdangerous: started
    Running setup.py install for itsdangerous: finished with status 'done'
  Running setup.py install for MarkupSafe: started
    Running setup.py install for MarkupSafe: finished with status 'done'
Successfully installed Jinja2-2.9.5 MarkupSafe-0.23 Werkzeug-0.11.15 click-6.7 flask-0.12 itsdangerous-0.24 redis-2.10.5
 ---> 6adce98b4bd0
Removing intermediate container 2dfe61c2537e
Step 5/5 : CMD python app.py
 ---> Running in 554d0f0d4635
 ---> c28028d2c0de
Removing intermediate container 554d0f0d4635
Successfully built c28028d2c0de
Starting dockercompose_redis_1
Starting dockercompose_db_1
Recreating dockercompose_web_1
Attaching to dockercompose_db_1, dockercompose_redis_1, dockercompose_web_1

Answer 1

I found my answer here .

I had to change these lines :

volumes:
  - ./webapp:/opt/webapp

to :

volumes:
  - .:/code

since this directory is the one that is mentioned in my Dockerfile. I could also change my Dockerfile instead.