ifrit v2: Cleanup and simplification of boilerplate in main

main_v1.go

// Old clunky way of setting up ifrit
package main

import ...

func main() {
  logger := newLogger("example-service")
  
  members := grouper.Members{
    {"http_server", httpServer},
    {"presence", initializeCellPresence(address, serviceClient, executorClient)},
    {"bulker", harmonizer.NewBulker(logger, *pollingInterval, *evacuationPollingInterval)},
    {"event-consumer", harmonizer.NewEventConsumer(logger, opGenerator, queue)},
    {"evacuator", evacuator},
  }

  if dbgAddr := cf_debug_server.DebugAddress(flag.CommandLine); dbgAddr != "" {
    members = append(grouper.Members{
      {"debug-server", cf_debug_server.Runner(dbgAddr, reconfigurableSink)},
    }, members...)
  }

  group := grouper.NewOrdered(os.Interrupt, members)

  monitor := ifrit.Invoke(sigmon.New(group, os.Interrupt, unix.SIGUSR1))

  logger.Info("started", lager.Data{"cell-id": *cellID})

  err = <-monitor.Wait()
  if err != nil {
    logger.Error("exited-with-failure", err)
    os.Exit(1)
  }

  logger.Info("exited")
}

main_v2.go

// New hotness
package main

import ...

func main() {
  // reusable logging boilerplate
  logger := lager.NewLogger("example-service")
  
  // grouper code moved to the ifrit package, signal option removed (always os.Interrupt)
  group := ifrit.NewOrderedGroup(ifrit.Members{
    // allow nil members that are ignored, like a disabled debug server
    ifrit.NewMember("debug-server", cf_debug_server.Runner(dbgAddr, reconfigurableSink)),
    ifrit.NewMember("http_server", httpServer),
    ifrit.NewMember("presence", initializeCellPresence(address, serviceClient, executorClient)),
    ifrit.NewMember("bulker", harmonizer.NewBulker(logger, *pollingInterval)),
    ifrit.NewMember("event-consumer", harmonizer.NewEventConsumer(logger, opGenerator, queue)),
    ifrit.NewMember("evacuator", evacuator}),
  })

  // Invoke and Background now take optional list of signals
  process := ifrit.Invoke(group, os.Interrupt, unix.SIGUSR1)
  
  logger.Info("started", lager.Data{"cell-id": *cellID})
  
  err := <- process.Wait()
  if err != nil {
    logger.Error("exited-with-failure", err)
    os.Exit(1)
  }
  
  logger.Info("exited")
}