Custom nginx container exits immediately when part

Question

I'm trying to learn how to use docker compose with a simple setup of an nginx container that reroutes requests to a ghost container. I'm using the standard ghost image but have a custom nginx image (that inherits from the standard image).

When I run the composition using "docker-compose up" it exits immediately with "docker_nginx_1 exited with code 0". However, when I build and run it manually, it runs fine and I can navigate my browser to the container and view the default nginx page. What am I misunderstanding about my compose file that causes it to behave differently than being custom built? What can I change to get it to stay running?

Disclaimer: I am also learning nginx as I go, so learning two things at once may be causing me undue problems.

EDIT: The original files were a bit more complex, but I've reduced the issue to simply: If I use the build command for a custom image that does nothing but inherit from the default nginx image, it exits immediately. If I use the default nginx image, it works. These are the now relevant files:

Compose file:

ghost:
 expose:
   - "2368"
 image: ghost

nginx:
  # image: nginx << If I use this instead of my custom build, it doesn't exit
  build: ./nginx
  ports:
    - "80:80"
    - "443:443"
  links:
   - ghost

nginx/Dockerfile:

FROM nginx

ORIGINAL FILES (with the same compose file as above):

nginx/Dockerfile:

FROM nginx
RUN rm /etc/nginx/nginx.conf
COPY conf/nginx.conf /etc/nginx/nginx.conf
COPY conf/sites-available/ghost /etc/nginx/sites-available/ghost
RUN mkdir /etc/nginx/sites-enabled
RUN ln -s /etc/nginx/sites-available/ghost /etc/nginx/sites-enabled/ghost

EXPOSE 80 443

# Is this even the right command I have no idea

CMD service nginx start

nginx/conf/nginx.conf:

daemon off;

user  nginx;
# Let nginx figure out the processes I guess
worker_processes  auto;

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


events {
    worker_connections  1024;
}

http {
    include       /etc/nginx/mime.types;
    default_type  application/octet-stream;

    log_format  main  '$remote_addr - $remote_user [$time_local] "$request" '
                      '$status $body_bytes_sent "$http_referer" '
                      '"$http_user_agent" "$http_x_forwarded_for"';

    access_log  /var/log/nginx/access.log  main;

    sendfile        on;
    #tcp_nopush     on;

    keepalive_timeout  65;

    #gzip  on;

    include /etc/nginx/conf.d/*.conf;
}

nginx/conf/sites-available/ghost

server {
  listen 80;
  server_name 127.0.0.1;
  access_log /var/log/nginx/localhost.log;

  location / {
    proxy_set_header X-Real-IP $remote_addr;
    proxy_set_header HOST $http_host;
    proxy_set_header X-NginX-Proxy true;

    proxy_pass http://0.0.0.0:2368;
    proxy_redirect off;
  }
}

Running compose-up:

plays-MacBook-Pro:docker play$ docker-compose up
Creating docker_ghost_1...
Creating docker_nginx_1...
Attaching to docker_ghost_1, docker_nginx_1
docker_nginx_1 exited with code 0
Gracefully stopping... (press Ctrl+C again to force)
Stopping docker_ghost_1... done

Running manually:

plays-MacBook-Pro:nginx play$ docker build --no-cache -t nginx_custom .
Sending build context to Docker daemon 8.704 kB
Step 0 : FROM nginx
 ---> 914c82c5a678
Step 1 : RUN rm /etc/nginx/nginx.conf
 ---> Running in 4ce9de96bb36
 ---> 98f97a9da4fc
Removing intermediate container 4ce9de96bb36
Step 2 : ADD conf/nginx.conf /etc/nginx/nginx.conf
 ---> dd3e089208a9
Removing intermediate container 36b9a47e0806
Step 3 : ADD conf/sites-available/ghost /etc/nginx/sites-available/ghost
 ---> 55fae53e5810
Removing intermediate container a82741d24af4
Step 4 : RUN mkdir /etc/nginx/sites-enabled
 ---> Running in 7659ead01b7b
 ---> 406be1c42394
Removing intermediate container 7659ead01b7b
Step 5 : RUN ln -s /etc/nginx/sites-available/ghost /etc/nginx/sites-enabled/ghost
 ---> Running in e9658a08affa
 ---> 021a84216e8a
Removing intermediate container e9658a08affa
Step 6 : EXPOSE 80 443
 ---> Running in 230e4523794c
 ---> 23d85e1a04cb
Removing intermediate container 230e4523794c
Step 7 : CMD service nginx start
 ---> Running in 209e129cae21
 ---> d7004d6fa223
Removing intermediate container 209e129cae21
Successfully built d7004d6fa223
plays-MacBook-Pro:nginx play$ docker run -t nginx_custom
[It sits here on an empty line, running in the background]

Answer 1

You can also add a

tty: true

to the service in your docker-compose.yml:

webserver:
    build: .
    volumes:
        - "./src:/var/www/html"
    ports:
        - 8080:80
    depends_on:
        - aap-mysql
    tty: true

and it should stay running after

docker-compose up

Answer 2

The CMD in your Dockerfile should start a process which needs to run in foreground. The command service nginx start runs the process in deamon mode and thus your container exits cleanly because the service command exits.

Use the following CMD ["nginx", "-g", "daemon off;"] to start nginx (taken from official image) and it should work correctly.

Answer 3

I figured out what it was. I needed to name the nginx part of my composition something other than 'nginx' . I'm not sure if it's because there is already an nginx image or if it is something else, but changing it made it work properly.

By changing my compose file to:

ghost:
 expose:
   - "2368"
 image: ghost

mything:
  # image: nginx
  build: ./nginx
  ports:
    - "80:80"
    - "443:443"
  links:
   - ghost

I was able to get it to work. An indicator was that when the name changed, I actually saw the build process output for my container. If anyone knows exactly why the naming needs to be that way, I'd love to know.

Answer 4

Just ran into this same issue, and the initial fix was to change the name of the service in docker-compose.yml.

This worked, but the reason it worked is because Docker-compose caches the build & ties it to the service name. Every docker-compose up after the first one just uses what it built before, so any changes you make to the Dockerfile, or that section of the docker-compose.yml are basically ignored.

When you (and I) changed the service name, it triggered a new build since that service name hasn't been tagged before.

The real solution is to do a: docker-compose build to rebuild the image (followed by a docker-compose up). Their documentation doesn't really emphasize this issue.