Reverse proxy in Traefik with subdirectories.

app.py

from flask import Flask
app = Flask(__name__)

@app.route('/')
def hello_world():
    return 'Hello, World!'

@app.route('/flask/')
@app.route('/flask/<int:post_id>')
def post(post_id=0):
    print(post_id)
    return 'Hello, Flask!'

docker-compose-flask-app.yml

version: "3"

services:

 client:
  image: alpine
  command: tail -f /dev/null

 flask:
  build: .
  ports:
   - 9080-9089:8080
  scale: 2
  labels:
    - "traefik.enable=true"
    - "traefik.http.routers.flask.entrypoints=front"
    - "traefik.http.routers.flask.rule=PathPrefix(`/flask{regex:$$|/.*}`)"
    - "traefik.http.routers.flask.middlewares=flask-stripprefix"
    - "traefik.http.middlewares.flask-stripprefix.stripprefix.prefixes=/"
  networks:
    - traefik01
    - traefik02

 httpd:
   image: httpd:2.4.41-alpine
   expose:
    - 80
   scale: 2
   labels:
    - "traefik.enable=true"
    - "traefik.http.routers.httpd.entrypoints=front"
    - "traefik.http.routers.httpd.rule=PathPrefix(`/httpd{regex:$$|/.*}`)"
    - "traefik.http.routers.httpd.middlewares=httpd-stripprefix"
    - "traefik.http.middlewares.httpd-stripprefix.stripprefix.prefixes=/httpd"
   networks:
    - traefik01
    - traefik02

networks:
  traefik01:
    external: true
  traefik02:
    external: true

docker-compose-simple-http.yml

version: "3"

services:

 simple_http:
  image: python:3.7.8-alpine
  working_dir: /data
  command: python -m http.server 5000
  ports:
   - 5000-5009:5000
  scale: 2
  labels:
    - "traefik.enable=true"
    - "traefik.http.routers.simple_http.entrypoints=front"
    - "traefik.http.routers.simple_http.rule=PathPrefix(`/simple_http{regex:$$|/.*}`)"
    - "traefik.http.routers.simple_http.middlewares=simple_http-stripprefix"
    - "traefik.http.middlewares.simple_http-stripprefix.stripprefix.prefixes=/"
  networks:
    - traefik01
    - traefik02

networks:
  traefik01:
    external: true
  traefik02:
    external: true

docker-compose-traefik-subdir.yml

version: '3.7'

services:

  traefik01:
    container_name: traefik01
    image: traefik:${TRAEFIK_IMAGE_VERSION:-v2.2.0}
    ports:
      - "81:80"
      - "8081:8080"
    environment:
      - TRAEFIK_LOG_LEVEL=INFO
      - TRAEFIK_ACCESSLOG=true
      - TRAEFIK_PROVIDERS_DOCKER_EXPOSEDBYDEFAULT=false
      - TRAEFIK_PROVIDERS_DOCKER=true
      - TRAEFIK_PROVIDERS_DOCKER_NETWORK=traefik01
      - TRAEFIK_API_INSECURE=true
      - TRAEFIK_ENTRYPOINTS_FRONT=true
      - TRAEFIK_ENTRYPOINTS_FRONT_ADDRESS=:80
    networks:
      - traefik01
    volumes:
      - /var/run/docker.sock:/var/run/docker.sock:ro
    security_opt:
      - label:type:docker_t

  traefik02:
    container_name: traefik02
    image: traefik:${TRAEFIK_IMAGE_VERSION:-v2.2.0}
    ports:
      - "82:80"
      - "8082:8080"
    environment:
      - TRAEFIK_LOG_LEVEL=INFO
      - TRAEFIK_ACCESSLOG=true
      - TRAEFIK_PROVIDERS_DOCKER_EXPOSEDBYDEFAULT=false
      - TRAEFIK_PROVIDERS_DOCKER=true
      - TRAEFIK_PROVIDERS_DOCKER_NETWORK=traefik02
      - TRAEFIK_API_INSECURE=true
      - TRAEFIK_ENTRYPOINTS_FRONT=true
      - TRAEFIK_ENTRYPOINTS_FRONT_ADDRESS=:80
    networks:
      - traefik02
    volumes:
      - /var/run/docker.sock:/var/run/docker.sock:ro
    security_opt:
      - label:type:docker_t

networks:
  traefik01:
    driver: bridge
    name: traefik01
  traefik02:
    driver: bridge
    name: traefik02

Dockerfile

FROM python:3.7.8-alpine
ENV PYTHONUNBUFFERED=1
ENV LC_ALL=C.UTF-8
ENV LANG=C.UTF-8

ENV FLASK_APP=app.py
ENV FLASK_RUN_HOST=0.0.0.0
ENV FLASK_RUN_PORT=8080

EXPOSE 8080

RUN mkdir -p /code/flask-app
WORKDIR /code/flask-app
COPY requirements.txt ./
RUN pip install -r requirements.txt
ADD . ./

CMD flask run

requirements.txt

flask
gunicorn

https://medium.com/@iced_burn/reverse-proxy-in-traefik-with-subdirectories-eef4261939e