Unknown MySQL server host 'db' Rails and Docker - mysql

Question

This is strange. I'm currently using Rails 5.1.5 with Docker and Docker-Compose. I am connecting to a remote MySQL (which is firewalled, and has limited access to. No, the database is not inside a docker container; it runs in its own server). I was able to run rails db:migrate and the schema was successfully created.
But, when I try to navigate to the part of the site which has a database call, it displays:
We're sorry, but something went wrong.
I went ahead and enabled STOUT logs to check for everything that was happening. It seems that there is a part in which it says:
Mysql2::Error (Unknown MySQL server host 'db'. (-2));
Note that 'db' is the host for my development environment. The production environment is another one.
I don't think this is a Docker problem (although I could be wrong)
This is the current database.yml:
default: &default
adapter: mysql2
pool: 5
encoding: utf8
database: <%= Rails.application.secrets.mysql_database %>
username: <%= Rails.application.secrets.mysql_username %>
password: <%= Rails.application.secrets.mysql_password %>
host: <%= Rails.application.secrets.mysql_host %>
port: 3306
development: *default
test:
<<: *default
database: db/test.sqlite3
production: *default
The current secrets.yml is as follows:
development:
secret_key_base: the_secret_key_base
mysql_database: <%= ENV["SECRET_MYSQL_DATABASE"] %>
mysql_username: <%= ENV["SECRET_MYSQL_USERNAME"] %>
mysql_password: <%= ENV["SECRET_MYSQL_PASSWORD"] %>
mysql_host: <%= ENV['SECRET_MYSQL_HOST'] %>
I am currently using
config.read_encrypted_secrets = true
And the encrypted secrets.yml.enc is:
This is the Docker-Compose file I'm currently using:
version: '3.2'
services:
app:
image: jja3324/ntid:cprintservicehub_app
restart: always
environment:
RAILS_ENV: production
# What this is going to do is that all the logging is going to be printed into the console.
# Use this with caution as it can become very verbose and hard to read.
# This can then be read by using docker-compose logs app.
RAILS_LOG_TO_STDOUT: 'true'
# The first command, the remove part, what it does is that it eliminates a file that
# tells rails and puma that an instance is running. This was causing issues,
# https://github.com/docker/compose/issues/1393
command: bash -c "rm -f tmp/pids/server.pid && bundle exec rails s -e production -p 5000 -b '0.0.0.0'"
volumes:
- /var/www/cprint
ports:
- "5000:5000"
expose:
- "5000"
# Uses Nginx as a web server (Access everything through http://localhost)
# https://stackoverflow.com/questions/30652299/having-docker-access-external-files
web:
image: jja3324/ntid:cprintservicehub_web
restart: always
links:
- app
volumes:
- type: bind
source: /path-to/ssl/certs
target: /path-to/ssl/certs
- type: bind
source: /path-to-private-ssl/private/
target: /path-to-private-ssl/private
links:
- app
ports:
- "80:80"
- "443:443"
Reading this answer tells me that Rails couldn't resolve the name for the MySQL server. I think this translates to Rails defaulting back to its original config.
Any ideas? Thanks :)

Answer 1

While I haven't solved entirely the problem (Can't connect to the Database yet) it seems this had something to do with Nginx, and config.force_sslin production.rb
Apparently, I had a bug in the Nginx configuration. I was missing setting the X-Forwarded-Proto https header in the configuration file. This was causing infinite redirects (which I honestly don't know why they weren't present the day before... I think it was because of the cookies in my browser).
After doing that, Rails is correctly using my configuration. I still have to figure out what's the problem (which seems to be a firewall issue).