Connect to hidden PostgreSQL database through SSH tunnel using Ruby

config

# This is my local config for the host I tunnel through in ~/.ssh/config
Host mypublichost
    HostName remote.hostname.com
    User remotesshusername
    Port remotesshport
    IdentityFile ~/.ssh/subfolder/id_rsa

Gemfile

source 'https://rubygems.org'
git_source(:github) { |repo| "https://github.com/#{repo}.git" }
ruby '2.5.7'
gem 'activerecord'
gem 'net-ssh-gateway'

with_ssh_config.rb

require 'active_record'
require 'net/ssh/gateway'

class CombinedHCP < ActiveRecord::Base
  self.table_name = 'schema.tablename'
  self.primary_key = 'uuid'
end

# set password nil to use public key authentication
gateway = Net::SSH::Gateway.new('mypublichost', nil)

# from the host, connect to the actual database instance, which is not public
port = gateway.open('hidden-prod-db.sdu29328dh.eu-central-1.rds.amazonaws.com', 5432)

ActiveRecord::Base.establish_connection(
  adapter: 'postgresql',
  host: '127.0.0.1',
  username: 'dbuser',
  password: 'dbpassword',
  database: 'dbname',
  port: port
)

CombinedHCP.all.limit(10).each do |hcp|
  puts hcp.attributes
end

gateway.close

without_ssh_config.rb

require 'active_record'
require 'net/ssh/gateway'

class CombinedHCP < ActiveRecord::Base
  self.table_name = 'schema.tablename'
  self.primary_key = 'uuid'
end

# set password nil to use public key authentication
# as an alternative to using the local ~/.ssh/config, you can also supply all host parameters directly
gateway = Net::SSH::Gateway.new('remote.hostname.com', nil, {
                                  user: 'remotesshusername',
                                  port: remotesshport,
                                  keys: ['~/.ssh/subfolder/id_rsa']
                                })

# from the host, connect to the actual database instance, which is not public
port = gateway.open('hidden-prod-db.sdu29328dh.eu-central-1.rds.amazonaws.com', 5432)

ActiveRecord::Base.establish_connection(
  adapter: 'postgresql',
  host: '127.0.0.1',
  username: 'dbuser',
  password: 'dbpassword',
  database: 'dbname',
  port: port
)

CombinedHCP.all.limit(10).each do |hcp|
  puts hcp.attributes
end

gateway.close