Load docker secrets into Rails

001_secrets.rb

# config/initializers/001_secrets.rb
# Loads docker secrets into ENV

# Example docker-compose.yml:
# 
# version: "3.4"
# services:
#   web:
#     image: myapp
#     build: .
#     ports:
#       - "3000:3000"
#     secrets:
#       - secret_api_key
#
# secrets:
#   secret_api_key:
#     external: true

# Now create your docker secret while on a machine in the swarm:
# $ echo "389rAa39wef9+q32jfqp0w9jrq0Zhtpq23hpa9=" | docker secret create secret_api_key -

Dir['/run/secrets/*'].each do |secret_file|
  next if secret_file =~ /\/$/
  name = secret_file.split('/')[-1]
  ENV[name.upcase] = File.read(secret_file).strip if name
end

# Now we have access to the docker secret:
# ENV['SECRET_API_KEY']
# => "389rAa39wef9+q32jfqp0w9jrq0Zhtpq23hpa9="