Cant connect to rails docker container on localhost - ruby-on-rails

Question

Im having trouble accessing my containerized rails app from my local machine. I'm following this quickstart guide as a template and made some tweaks to the paths for my gemfile and gemfile.lock. The quickstart guide moves on to docker-compose, but I want to try accessing the app without it first to get familiar with these processes before moving on.
This is my dockerfile:
FROM ruby:2.5
RUN apt-get update -qq && apt-get install -y nodejs postgresql-client
RUN mkdir /myapp
WORKDIR /myapp
COPY Gemfile ./Gemfile
COPY Gemfile.lock ./Gemfile.lock
RUN gem install bundler -v 2.0.1
RUN bundle install
COPY . /myapp
# Add a script to be executed every time the container starts.
COPY entrypoint.sh /usr/bin/
RUN chmod +x /usr/bin/entrypoint.sh
ENTRYPOINT ["entrypoint.sh"]
EXPOSE 3000:3000
# Start the main process.
CMD ["rails", "server", "-b", "0.0.0.0"]
and this is the entrypoint file:
#!/bin/bash
set -e
# Remove a potentially pre-existing server.pid for Rails.
rm -f /myapp/tmp/pids/server.pid
# Then exec the container's main process (what's set as CMD in the Dockerfile).
exec "$#"
I am able to successfully build and run the image, but when I try to access 0.0.0.0:3000 I get a cant connect error.
I also attached a screenshot of my app directory structure, the Dockerfile and entrypoint are at the root.
One thing that seems strange is when I try to run the logs for the container I dont get any output, but when I shut the container down I see the startup logs. Not sure why that is.
I am running docker desktop 2.1.0.3. Any thoughts/help are very appreciated.

Answer 1

use just EXPOSE 3000 in dockerfile.
run container ror with mapping port to localhost from your new docker image <image>
docker run -d --name ror -p 3000:3000 <image>
now you should be able to access localhost:3000

Answer 2

Here's an example of mine that works:
The usual dockerfile, nothing special here.
Then, in docker-compose.yml, add environment variable, or place in .env file, the DATABASE_URL (important bit is using the host.docker.internal instead of localhost
Then in your database.yml, specify the url with the ENV key
Then start the container by running docker-compose up
#Dockerfile
FROM ruby:3.0.5-alpine
RUN apk add --update --no-cache \
bash \
build-base \
tzdata \
postgresql-dev \
yarn \
git \
curl \
wget \
gcompat
COPY Gemfile Gemfile.lock ./
WORKDIR /app
RUN curl -sL https://deb.nodesource.com/setup_14.x | bash
RUN gem install bundler:2.4.3
RUN bundle lock --add-platform x86_64-linux
RUN bundle install
COPY package.json yarn.lock ./
RUN yarn install
COPY . .
EXPOSE 3000
CMD ["rails", "server", "-b", "0.0.0.0", "--pid=/tmp/server.pid"]
#docker-compose.yml
version: "3.9"
services:
app:
image: your_app_name
volumes:
- /app
env_file:
- .env
environment:
- DATABASE_URL=postgresql://postgres#host.docker.internal:5432/<your_db_name>
ports:
- "3000:3000"
webpack_dev_server:
build: .
command: bin/webpack-dev-server
ports:
- "3035:3035"
volumes:
- /app
env_file:
- .env
environment:
- WEBPACKER_DEV_SERVER_HOST=0.0.0.0
redis:
image: redis
#database.yml
development:
<<: *default
database: giglifepro_development
url: <%= ENV.fetch('DATABASE_URL') %>