"Welcome to Nginx!" - Docker-Compose, using uWSGI, Flask, nginx - docker

Question

My Problem:
I am using Ubuntu 18.04 and a docker-compose based solution with two Docker images, one to handle Python/uWSGI and one for my NGINX reverse proxy. No matter what I change, it always seems like WSGI is unable to detect my default application. Whenever I run docker-compose up, and navigate to localhost:5000 I get the above default splash.
The complete program appears to work on our CentOS 7 machines. However, when I try to execute it on my Ubuntu test machine, I can only get the "Welcome to NGINX!" page.
Directory Structure:
/app
- app.conf
- app.ini
- app.py
- docker-compose.py
- Dockerfile-flask
- Dockerfile-nginx
- requirements.txt
/templates
(All code snippets have been simplified to help isolate the problem)
Here is an example of my docker traceback:
clocker_flask_1
[uWSGI] getting INI configuration from app.ini
current working directory: /app
detected binary path: /usr/local/bin/uwsgi
uwsgi socket 0 bound to TCP address 0.0.0.0:5000 fd 3
*** WARNING: you are running uWSGI as root !!! (use the --uid flag) ***
*** Operational MODE: preforking+threaded ***
WSGI app 0 (mountpoint='') ready in 1 seconds on interpreter 0x558072010e70 pid: 1 (default app)
clocker_nginx_1
/docker-entrypoint.sh: /docker-entrypoint.d/ is not empty, will attempt to perform configuration
/docker-entrypoint.sh: Looking for shell scripts in /docker-entrypoint.d/
/docker-entrypoint.sh: Launching /docker-entrypoint.d/10-listen-on-ipv6-by-default.sh
10-listen-on-ipv6-by-default.sh: Getting the checksum of /etc/nginx/conf.d/default.conf
10-listen-on-ipv6-by-default.sh: Enabled listen on IPv6 in /etc/nginx/conf.d/default.conf
/docker-entrypoint.sh: Launching /docker-entrypoint.d/20-envsubst-on-templates.sh
/docker-entrypoint.sh: Configuration complete; ready for start up
Here is my docker-compose.yaml:
# docker-compose.yml
version: '3'
services:
flask:
image: webapp-flask
build:
context: .
dockerfile: Dockerfile-flask
volumes:
- "./:/app:z"
- "/etc/localtime:/etc/localtime:ro"
environment:
- "EXTERNAL_IP=${EXTERNAL_IP}"
nginx:
image: webapp-nginx
build:
context: .
dockerfile: Dockerfile-nginx
ports:
- 5000:80
depends_on:
- flask
Dockerfile-flask:
FROM python:3
ENV APP /app
RUN mkdir $APP
WORKDIR $APP
EXPOSE 5000
COPY requirements.txt .
RUN pip install -r requirements.txt
COPY . .
CMD [ "uwsgi", "--ini", "app.ini" ]
Dockerfile-nginx
FROM nginx:latest
EXPOSE 80
COPY app.conf /etc/nginx/conf.d
app.conf
server {
listen 80;
root /usr/share/nginx/html;
location / { try_files $uri #app; }
location #app {
include uwsgi_params;
uwsgi_pass flask:5000;
}
}
app.py
# Home bit
#application.route('/')
#application.route('/home', methods=["GET", "POST"])
def home():
return render_template(
'index.html',
er = er
)
if __name__ == "__main__":
application.run(host='0.0.0.0')
app.ini
[uwsgi]
protocol = uwsgi
module = app
callable = application
master = true
processes = 2
threads = 2
socket = 0.0.0.0:5000
vacuum = true
die-on-term = true
max-requests = 1000

Answer 1

The nginx image comes with a main configuration file, /etc/nginx/nginx.conf, which loads every conf file in the conf.d folder -- including your nemesis in this case, a stock /etc/nginx/conf.d/default.conf. It reads as follows (trimmed a bit for concision):
server {
listen 80;
server_name localhost;
location / {
root /usr/share/nginx/html;
index index.html index.htm;
}
}
So, your app.conf and this configuration are both active. The reason why this default one wins, though, is because of the server_name directive that it has (and yours lacks) -- when you're hitting localhost:5000, nginx matches based on the hostname and sends your request there.
To fix this easily, you can just remove that file in your Dockerfile-nginx:
RUN rm /etc/nginx/conf.d/default.conf