A ruby script that will wait for a port to be connectable on a host, normally used to check if another Docker container has booted up

wait-for-db

#!/usr/bin/env ruby
require "socket"
require "uri"

if ENV["DATABASE_URL"]
  url = URI.parse ENV["DATABASE_URL"]

  puts "Waiting for DB on #{url}..."
  30.times do
    begin
      TCPSocket.new(url.host, url.port || 5432)
      puts "Success!"
      exit 0
    rescue => e
      print "."
    end
    sleep 1
  end

  exit 1
else
  STDERR.puts "No DATABASE_URL env var is set, skipping"
end