host not found in upstream error caused by docker-compose - docker

Question

tldr-version: I have no idea whats causing this error. im pretty sure its not the line endings because i changed them manually with notepad++ (unless i need to change more than entrypoint.sh because thats all i changed the line endings on).
original post below.
I have no idea what is causing this error caused when i do docker-compose -f docker-compose-deploy.yml up --build into my command line i get the following output
Use 'docker scan' to run Snyk tests against images to find vulnerabilities and learn how to fix them
Starting mygoattheend-copy_app_1 ... done
Starting mygoattheend-copy_proxy_1 ... done
Attaching to mygoattheend-copy_app_1, mygoattheend-copy_proxy_1
app_1 | exec /scripts/entrypoint.sh: no such file or directory
proxy_1 | /docker-entrypoint.sh: /docker-entrypoint.d/ is not empty, will attempt to perform configuration
proxy_1 | /docker-entrypoint.sh: Looking for shell scripts in /docker-entrypoint.d/
proxy_1 | /docker-entrypoint.sh: Launching /docker-entrypoint.d/10-listen-on-ipv6-by-default.sh
proxy_1 | 10-listen-on-ipv6-by-default.sh: info: can not modify /etc/nginx/conf.d/default.conf (read-only file system?)
proxy_1 | /docker-entrypoint.sh: Launching /docker-entrypoint.d/20-envsubst-on-templates.sh
proxy_1 | /docker-entrypoint.sh: Launching /docker-entrypoint.d/30-tune-worker-processes.sh
proxy_1 | /docker-entrypoint.sh: Configuration complete; ready for start up
mygoattheend-copy_app_1 exited with code 1
proxy_1 | 2022/11/03 18:51:39 [emerg] 1#1: host not found in upstream "app" in /etc/nginx/conf.d/default.conf:9
proxy_1 | nginx: [emerg] host not found in upstream "app" in /etc/nginx/conf.d/default.conf:9
mygoattheend-copy_proxy_1 exited with code 1
Other examples of errors that appear when i search for nginx: [emerg] host not found in upstream "app" in /etc/nginx/conf.d/default.conf:9 online suggest the problem is due to missing -depends_on: so ive included my docker-compose file below but i followed the tutorial perfectly and his worked fine. And my docker-compose-deploy has its
-depends_on:
my full docker compose is below
version: '3.7'
services:
app:
build:
context: .
ports:
- "8000:8000"
volumes:
- ./app:/app
command: sh -c "python manage.py runserver 0.0.0.0:8000"
environment:
- DEBUG=1
My full docker-compose-deploy.yml is below
version: '3.7'
services:
app:
build:
context: .
volumes:
- static_data:/vol/web
environment:
- SECRET_KEY=samplesecretkey123
- ALLOWED_HOSTS=127.0.0.1,localhost
proxy:
build:
context: ./proxy
volumes:
- static_data:/vol/static
ports:
- "8080:8080"
depends_on:
- app
volumes:
static_data:
the image below is my full directory
The error does mention that it can't find app, which i copy with the main dockerfile (not the one in the proxy folder)
My main dockerfile is below.
FROM python:3.8-alpine
ENV PATH="/scripts:${PATH}"
COPY ./requirements.txt /requirements.txt
RUN apk add --update --no-cache --virtual .tmp gcc libc-dev linux-headers
RUN pip install -r /requirements.txt
RUN apk del .tmp
RUN mkdir /app
COPY ./app /app
WORKDIR /app
COPY ./scripts /scripts
RUN chmod +x /scripts/*
RUN mkdir -p /vol/web/media
RUN mkdir -p /vol/web/
RUN adduser -D user
RUN chown -R user:user /vol
RUN chmod -R 755 /vol/web
USER user
CMD ["entrypoint.sh"]
what could be causing this error?
what other info do you need to work it out?
im following this tutorial. im at the very end https://www.youtube.com/watch?v=nh1ynJGJuT8
update 1 (adding extra info)
my proxy/default.conf is below
server {
listen 8080;
location /static {
alias /vol/static;
}
location / {
uwsgi_pass app:8000;
include /etc/nginx/uwsgi_params;
}
}
my proxy/dockerfile is below
FROM nginxinc/nginx-unprivileged:1-alpine
COPY ./default.conf /etc/nginx/conf.d/default.conf
COPY ./uwsgi_params /etc/nginx/uwsgi_params
USER root
RUN mkdir -p /vol/static
RUN chmod 755 /vol/static
USER nginx
update 2
this is my whole project uploaded to github https://github.com/tgmjack/help
update 3
editing the line endings in vscode didnt appear to work.
update 4
new dockerfile trying dos2unix
FROM python:3.8-alpine
ENV PATH="/scripts:${PATH}"
COPY ./requirements.txt /requirements.txt
RUN apk add --update --no-cache --virtual .tmp gcc libc-dev linux-headers dos2unix
RUN pip install -r /requirements.txt
RUN apk del .tmp
RUN mkdir /app
COPY ./app /app
WORKDIR /app
COPY ./scripts /scripts
RUN chmod +x /scripts/*
RUN mkdir -p /vol/web/media
RUN mkdir -p /vol/web/
RUN adduser -D user
RUN chown -R user:user /vol
RUN chmod -R 755 /vol/web
USER user
CMD ["dos2unix", "entrypoint.sh"]
but i still get the same error.
update 5
ok so i changed the eol of entrypoint.sh manually with notepad++ but i still get the same error.
do i need to apply this to more than just entrypoint.sh?

Answer 1

There are two problems in this setup.
DOS line endings
The first problem is the use of DOS line endings on the entrypoint. Here's what I see when I use od to get a character-by-character dump of the files:
$ od -c scripts/entrypoint.sh | head -n 2
0000000 # ! / b i n / s h \r \n \r \n s e t
0000020 - e \r \n \r \n p y t h o n m a
The issue is that after #!/bin/sh, we have \r\n, when we should have just \n. This is a DOS-style line ending, but Linux expects just a \n. More information
I used a program called dos2unix to replace those lines:
$ dos2unix scripts/entrypoint.sh
dos2unix: converting file scripts/entrypoint.sh to Unix format...
(VS code can do this too - here's how.)
When I run it, I get a new error:
app_1 | Traceback (most recent call last):
app_1 | File "manage.py", line 21, in <module>
app_1 | main()
app_1 | File "manage.py", line 17, in main
app_1 | execute_from_command_line(sys.argv)
app_1 | File "/usr/local/lib/python3.8/site-packages/django/core/management/__init__.py", line 401, in execute_from_command_line
app_1 | utility.execute()
app_1 | File "/usr/local/lib/python3.8/site-packages/django/core/management/__init__.py", line 345, in execute
app_1 | settings.INSTALLED_APPS
app_1 | File "/usr/local/lib/python3.8/site-packages/django/conf/__init__.py", line 76, in __getattr__
app_1 | self._setup(name)
app_1 | File "/usr/local/lib/python3.8/site-packages/django/conf/__init__.py", line 63, in _setup
app_1 | self._wrapped = Settings(settings_module)
app_1 | File "/usr/local/lib/python3.8/site-packages/django/conf/__init__.py", line 142, in __init__
app_1 | mod = importlib.import_module(self.SETTINGS_MODULE)
app_1 | File "/usr/local/lib/python3.8/importlib/__init__.py", line 127, in import_module
app_1 | return _bootstrap._gcd_import(name[level:], package, level)
app_1 | File "<frozen importlib._bootstrap>", line 1014, in _gcd_import
app_1 | File "<frozen importlib._bootstrap>", line 991, in _find_and_load
app_1 | File "<frozen importlib._bootstrap>", line 975, in _find_and_load_unlocked
app_1 | File "<frozen importlib._bootstrap>", line 671, in _load_unlocked
app_1 | File "<frozen importlib._bootstrap_external>", line 843, in exec_module
app_1 | File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
app_1 | File "/app/app/settings.py", line 31, in <module>
app_1 | ALLOWED_HOSTS.extend(ALLOWED_HOSTS.split(',')) # .split(",") = incase multiple so we seperate them with a comma
app_1 | AttributeError: 'list' object has no attribute 'split'
Wrong variable referenced in settings file
I edited the file app/app/settings.py, and changed this line
ALLOWED_HOSTS.extend(ALLOWED_HOSTS.split(','))
to
ALLOWED_HOSTS.extend(ALLOWED_HOSTS_ENV.split(','))
After this, I found this worked.
Nginx
The nginx configuration turned out to be fine. The issue was that the app died, so nginx couldn't do a DNS lookup to find the IP address of the app container. Fixing the app container also fixes nginx.