how to access rails app runing inside docker container

Question

I am using Dockerfile to build docker container for basic rails blog app. here is my Dockerfile

FROM ruby:2.3

RUN apt-get update \
    && apt-get install -y --no-install-recommends \
        postgresql-client \
    && rm -rf /var/lib/apt/lists/*

WORKDIR /usr/src/app
COPY Gemfile* ./
RUN bundle install
COPY . .

EXPOSE 8000
CMD rails server -p 8000 -b 0.0.0.0 

then I ran this command to build docker image

docker build -t blog .

and here is how I ran container from docker image

docker run -d -e POSTGRES_USER=$POSTGRES_USER -e POSTGRES_PASSWORD=$POSTGRES_PASSWORD --net=blog --name app -v $PWD:/usr/src/app -p 8000:8000 blog

after accessing logs from container I got this

docker logs app
=> Booting Puma
=> Rails 5.1.6.1 application starting in development 
=> Run `rails server -h` for more startup options
Puma starting in single mode...
* Version 3.12.0 (ruby 2.3.8-p459), codename: Llamas in Pajamas
* Min threads: 5, max threads: 5
* Environment: development
* Listening on tcp://0.0.0.0:3000
Use Ctrl-C to stop

After googling 2 hours I got some click that its a conflict in rails 5.1 that run tcp://0.0.0.0:3000 in rails. So I switched my application server from PUMA to WEBRICK. now the docker logs app says:

docker logs app
[2018-12-06 12:30:10] INFO  WEBrick 1.3.1
[2018-12-06 12:30:10] INFO  ruby 2.3.8 (2018-10-18) [x86_64-linux]
[2018-12-06 12:30:10] INFO  WEBrick::HTTPServer#start: pid=8 port=3000

but the application is still not accessible from firefoix/chrom. Please guide if I am doing something wrong. TIA :)

Answer 1

Just an off the cuff suggestion:

Try:

docker run -d -e POSTGRES_USER=$POSTGRES_USER -e POSTGRES_PASSWORD=$POSTGRES_PASSWORD --net=blog --name app -v $PWD:/usr/src/app -p 3000:3000 blog

If you can resolve that perhaps the following is not being applied as you expect.

EXPOSE 8000
CMD rails server -p 8000 -b 0.0.0.0