Docker Compose with NGINX proxy pass thru not working - docker

Question

Following is my Docker Compose file & NGINX conf file.
The application seems to work and NGINX is also up, but the proxy_pass setting doesn't seem to work properly.
File
docker-compose.yaml
networks:
webapp:
services:
web:
image: nginx
volumes:
- ./data/ntemplates:/etc/nginx/templates
- ./webapp.conf:/etc/nginx/conf.d/webapp.conf
ports:
- "8080:80"
networks:
- webapp
pyweb:
build: .
ports:
- "5000:5000"
networks:
- webapp
redis:
image: "redis:alpine"
networks:
- webapp
File webapp.conf
server {
listen 80;
listen [::]:80;
server_name localhost;
location / {
proxy_pass "http://pyweb_1:5000/";
}
#error_page 404 /404.html;
error_page 500 502 503 504 /50x.html;
}
Service pyweb is working if properly if directly accessed by http://pyweb_1:5000
I created this app based on docker getting started page
For completeness below are other files and seems to be working just fine.
File Dockerfile
FROM python:3.7-alpine
WORKDIR /code
ENV FLASK_APP=app.py
ENV FLASK_RUN_HOST=0.0.0.0
RUN apk add --no-cache gcc musl-dev linux-headers
COPY requirements.txt requirements.txt
RUN pip install -r requirements.txt
EXPOSE 5000
COPY . .
CMD ["flask", "run"]FROM python:3.7-alpine
WORKDIR /code
ENV FLASK_APP=app.py
ENV FLASK_RUN_HOST=0.0.0.0
RUN apk add --no-cache gcc musl-dev linux-headers
COPY requirements.txt requirements.txt
RUN pip install -r requirements.txt
EXPOSE 5000
COPY . .
CMD ["flask", "run"]
File requirement.txt
flask
redis
File app.py
import time
import redis
from flask import Flask
app = Flask(__name__)
cache = redis.Redis(host='redis', port=6379)
def get_hit_count():
retries = 5
while True:
try:
return cache.incr('hits')
except redis.exceptions.ConnectionError as exc:
if retries == 0:
raise exc
retries -= 1
time.sleep(0.5)
#app.route('/')
def hello():
count = get_hit_count()
return 'Hello World! I have been seen {} times.\n'.format(count)

Answer 1

EDIT:
You're currently not using the nginx configuration. I didn't read carefully your docker-compose file. You can fix it by mapping the webapp.conf on /etc/nginx/conf.d/default.conf. e.g.
services:
web:
image: nginx
volumes:
- ./data/ntemplates:/etc/nginx/templates
- ./webapp.conf:/etc/nginx/conf.d/default.conf
ports:
- "8080:80"
depends_on:
- pyweb
networks:
- webapp
There are 2 issues:
you don't know what container name will be used by docker-compose
you don't know the order used to start the containers
docker-compose allows you to solve the first issue in 2 ways:
define a container_name subsection
use the service name
This means that you can simply use proxy_pass "http://pyweb:5000/"; in your nginx setup
The second issue can be fixed by adding a depends_on subsection in the nginx service. e.g.
services:
web:
image: nginx
volumes:
- ./data/ntemplates:/etc/nginx/templates
- ./webapp.conf:/etc/nginx/conf.d/webapp.conf
depends_on:
- pyweb
ports:
- "8080:80"
networks:
- webapp
Nevertheless, the depends_on might not be enough since it does not check the service status but it only make sure that the docker service is started (as stated in the documentation).
You'll need to find another way to monitor if the service is actually started.