Supervisor - 0 downtime deployments

supervisor.rb

# No Downtime Deploys
# to setup
# clone your app in ~/app-a and ~/app-b
# use the following caddy server config
# yourdomain.com {
# reverse_proxy * {
#    to http://127.0.0.1:4210 http://127.0.0.1:4220
#    header_up +Host yourdomain.com
#    header_up -X-Forwarded-Host
#    health_uri /up
#    health_interval 1s
#    health_timeout 1s
#  }
#}
# To trigger a deploy:
# use github ssh action to `ssh user@server touch redeploy.txt`
#
# To run this in the background, use unix tools... 

require "net/http"
HOMEDIR = "/home/myapp".freeze # with no trailing slash
REDEPLOY_FILE = "#{HOMEDIR}/redeploy.txt".freeze

App = Struct.new(:name, :port, :pid) do
  def deploy = `cd #{name} && git pull && bundle && ./bin/rails db:migrate`

  def kill
    return unless pid

    Process.kill("SIGTERM", pid)
    Process.wait(pid)
    self.pid = nil
  end

  def redeploy
    puts "redeploying #{self}"
    kill
    deploy
    self.pid = spawn("./bin/rails server -p #{port}", chdir: "#{HOMEDIR}/#{name}")
    puts "waiting for #{self} to come up" until alive?
  end

  def to_s
    "#{name} alive? #{alive?} port: #{port} pid: #{pid}"
  end

  def alive?
    sleep 1
    Net::HTTP.get_response(URI("http://localhost:#{port}/up")).code == "200"
  rescue Errno::ECONNREFUSED
    puts "Connection refused"
    false
  end
end

apps = [
  App.new(name: "app-a", port: "4210"),
  App.new(name: "app-b", port: "4220")
]

at_exit { apps.each(&:kill) }

loop do
  puts apps
  if File.exist?(REDEPLOY_FILE)
    apps.each(&:redeploy)
    File.delete(REDEPLOY_FILE)
  end
end