Notify when daemon is ready

[rht]

Fixes #752

[rht]

For #862, one way is to reuse daemonFunc in cmd/ipfs/daemon.go, add

//early on
readyErrc := make(chan error)
res.SetOutput(readyErrc)
...
//after the "Daemon is ready" message
readyErrc <- nil

To use this in other place

daemonExit := make(chan error)
go func(){
  daemonFunc(req, res)
  daemonExit <- res.Error()
}()

for {
  select {
    case <-res.Output():
      // daemon is ready
    case <-daemonExit:
      // daemon exit
      break
  }
}

[jbenet]

Will this be the last thing printed even in light of scheduler fun, or slow-to-start HTTP servers and so on?

[rht]

ok, likely not. Need to check the ports of each server.

[jbenet]

as long as it's the last thing printed, it can be ok. servers dont have to be checked explicitly. maybe we can do this with a wait group? (add N to the wait group, and do wg.Done() as the lines are printed. the last one is:

go func () {
  wg.Wait()
  fmt.Println("Daemon is ready!")
}()

[rht]

The message will surely print last among the other server messages.

However, each of the messages, e.g. fmt.Printf("Gateway (writable) server listening on %s\n", gatewayMaddr) prints before each server runs.

If this is ok (servers don't have to be running, as long as the daemon ready msg prints last), then the pr is ok.

[jbenet]

ok sounds good