通过docker共享数据在两个python服务器之间撰写

Question

sharing a buffer of doubles between two python webservers(collector and calculator) over docker-compose

I am trying to simply send a buffer or an array of integers from a python server called collector to another one called calculator. calculator server should perfom simple mathimatical algorithim. This is all a trial. collector and calculator python scripts are runned in docker-compose in two containers and designed to be connected to the same network.

collector python script

app=Flask(__name__)

@app.route('/')
def index():
    d={"my_number": list(range(10))}
    return jsonify(d)

calculator python script

import requests

r=requests.get('https://collector:5000')

app = Flask(__name__)
@app.route('/')
def index():
    numbers_array = r.json()["my_numbers"]
    x=numbers_array[1] + numbers_array[2]
    return '{}'.format(x)

docker-compose.yml

services:
  collector:
    build: .
    env_file:
      - collector.env
    ports:
      - '5000:5000'
    volumes:
      - '.:/app'
    networks:
      - my_network



  calculator:
    build: ./calculator
    depends_on:
      - collector
    env_file:
      - calculator.env
    ports:
      - '5001:5000'
    volumes:
      - './calculator:/app'
    networks:
      - my_network

networks:
  my_network:
    driver: bridge

Dockerfile for both images is the same

FROM python:2.7-slim

RUN mkdir /app
WORKDIR /app

COPY requirements.txt requirements.txt
RUN pip install -r requirements.txt

COPY . .

LABEL maintainer="Mahmoud KD"

VOLUME ["/app/public"]

CMD flask run --host=0.0.0.0 --port=5000

when I run the docker-compose up --build, the first server,collector is achievable on my computer host and is working fine. The second server, calculator, fails to connect to collector via request.get. I tried to ping collector from calculator container while the docker-compose is running the two containers and the ping didn't function, it says " executable file not found in PATH: unknown". it seems that the connection of the two containers is not established although while doing inspection of my_network it shows the two containers. Can any body tell me what I am doing wrong. I am very grateful...

Answer 1

Use expose instead

one app on port 5000 other on port 5001

docker-compose:

app1:

expose:
  - 5000

app2:

expose:
  - 5001  

make sure you run apps with ip=0.0.0.0

If you want to access app 2 from hostmachine, forward ports

app2:

expose:
  - 5001
ports:
  - 80:5001

Explanation:

Expose only reveales ports inside docker world. So if you expose container's A port 8888, all other containers will be able to access that container at that port. But you will never reach it from host machine.

Standard procedure is that you forward only one port, that is 80 from security reasons and the rest of traffic is unreachable from outside world

---

Also change dockerfile. You dont want hardcoded ports

---

Edit:

Also get rid of this

volumes:
  - '.:/app'

It may actually cause extra troubles

---

Working Example: - it works, but the provided app contains errors

docker-compose.yml

version: '3.5'

services:
  collector:
    container_name: collector
    build:
      context: collector/.
    ports:
      - '80:5555'
    expose:
      - '5555'


  calculator:
    container_name: calculator
    build:
      context: calculator/.
    depends_on:
      - collector
    expose:
      - 6666
    ports:
      - '81:6666'
    volumes:
      - './calculator:/app'

You can access both endpoints on ports 80 and 81. Communication between both endpoints are hidden from us and its on 5555 and 6666. If you close 81(or 80), you can access the other endpoint only as 'proxy'