add a configurable pause before step_connect to work around bootstrap race conditions

helper/communicator/config.go

@@ -66,6 +66,9 @@ type Config struct {
 	WinRMInsecure           bool          `mapstructure:"winrm_insecure"`
 	WinRMUseNTLM            bool          `mapstructure:"winrm_use_ntlm"`
 	WinRMTransportDecorator func() winrm.Transporter
+
+	// Delay
+	PauseBeforeConnect time.Duration `mapstructure:"pause_before_connecting"`
 }
 
 // ReadSSHPrivateKeyFile returns the SSH private key bytes

helper/communicator/step_connect.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"fmt"
 	"log"
+	"time"
 
 	"github.com/hashicorp/packer/communicator/none"
 	"github.com/hashicorp/packer/helper/multistep"
@@ -44,9 +45,28 @@ type StepConnect struct {
 	substep multistep.Step
 }
 
+func (s *StepConnect) pause(pauseLen time.Duration, ctx context.Context) bool {
+	// Use a select to determine if we get cancelled during the wait
+	log.Printf("Pausing before connecting...")
+	select {
+	case <-ctx.Done():
+		return true
+	case <-time.After(pauseLen):
+	}
+	log.Printf("Pause over; connecting...")
+	return false
+}
+
 func (s *StepConnect) Run(ctx context.Context, state multistep.StateBag) multistep.StepAction {
 	ui := state.Get("ui").(packer.Ui)
 
+	if s.Config.PauseBeforeConnect > 0 {
+		cancelled := s.pause(s.Config.PauseBeforeConnect, ctx)
+		if cancelled {
+			return multistep.ActionHalt
+		}
+	}
+
 	typeMap := map[string]multistep.Step{
 		"none": nil,
 		"ssh": &StepConnectSSH{

website/source/docs/templates/communicator.html.md

@@ -198,3 +198,22 @@ The WinRM communicator has the following options.
 -   `winrm_use_ssl` (boolean) - If `true`, use HTTPS for WinRM.
 
 -   `winrm_username` (string) - The username to use to connect to WinRM.
+
+## Pausing Before Connecting
+We recommend that you enable SSH or WinRM as the very last step in your
+guest's bootstrap script, but sometimes you may have a race condition where
+you need Packer to wait before attempting to connect to your guest.
+
+If you end up in this situation, you can use the template option
+`pause_before_connecting`. By default, there is no pause. For example:
+
+{
+  "communicator": "ssh"
+  "ssh_username": "myuser",
+  "pause_before_connecting": "10m"
+}
+
+In this example, Packer will wait 10 minutes before attempting to connect to
+the guest.
+
+