Environment Variables Not Inherited by Worker Processes in Docker Container

[belmin-devops-eng]

Description:
I need to pass a few environment variables to the worker processes because I am using another module that requires specific environment variables to be passed. However, I am experiencing an issue where environment variables set in the master process are not inherited by the worker processes when running Nginx in a Docker container. Despite using the env directive in the nginx.conf file and setting environment variables correctly, the worker processes do not seem to have access to these variables.

I can see the variables I set when I list the environment variables in the container, but they are not present in /proc/PID_of_nginx_worker/environ.

Steps to Reproduce:

1. Set environment variables and run the container:

   docker run --privileged -d -it -p 8080:80 \
     -e TZ="some_value" -e TEST_ENV_VARIABLE="some_value" \
     -v /path/to/nginx.conf:/etc/nginx/nginx.conf nginx:latest

2. Add the env directive to the nginx.conf file:

   env TZ;
   env TEST_ENV_VARIABLE;

Expected Behavior:
The worker processes should inherit the environment variables TZ and TEST_ENV_VARIABLE from the master process and be accessible in /proc/PID_of_nginx_worker/environ.

Actual Behavior:
The worker processes do not inherit the environment variables, and they are not accessible.

How to Check:
You can verify the environment variables in the worker processes using the following script:

for pid in /proc/[0-9]*; do
  echo -n "PID: $(basename $pid) "
  cat $pid/cmdline
  echo
done

# Example output:
# PID: 1 nginx: master process nginx -g daemon off;
# PID: 2 nginx: worker process

cat /proc/2/environ
# No output

Any guidance or solutions to ensure environment variables are correctly inherited by worker processes would be greatly appreciated.

Thank you for your assistance!

[thresheek]

Hi @belmin-devops-eng!

This seems to work fine, however I indeed do not see the variables in environ for worker processes (but I don't think Linux guarantees that to be correct anyway):

user  nginx;
worker_processes  auto;

load_module /etc/nginx/modules/ngx_http_perl_module.so;

error_log  /var/log/nginx/error.log notice;
pid        /var/run/nginx.pid;

env FOOBAR;

events {
    worker_connections  1024;
}

http {
    perl_set $vari 'sub { return $ENV{"FOOBAR"}; }';

    server {
        listen 8080;
        location / {
            return 200 'OK: \'$vari\'\n';
        }
    }
}

$ docker run -e FOOBAR=baz -p 8080:8080 -v $(pwd)/nginx.conf:/etc/nginx/nginx.conf -d nginx:alpine-perl
3c66a3033f8165327fecce97b3e62d1a298b6871d1e139e7f672c39c9e5da98b
$ curl http://127.0.0.1:8080/
OK: 'baz'

[belmin-devops-eng]

Hi @thresheek!

Thank you for your quick response! I will explore alternative methods to ensure my module can establish the necessary connections. Thanks again for your assistance!

[marsboy02]

I found it interesting that Docker and nginx are being used together, so I did some research and found a reference stating that the TZ environment variable is implicitly inherited by the worker processes.

Reference: https://nginx.org/en/docs/ngx_core_module.html#env

For your information, when you run a Docker container with the -e parameter, these are treated as Linux environment variables within the container (you can verify this by running the 'env' command via docker exec). I hope this reference is very helpful for your work. Have a nice day!