command/build: -parallel=false to disable parallelization [GH-924]

CHANGELOG.md

@@ -10,6 +10,8 @@ FEATURES:
 IMPROVEMENTS:
 
 * builder/vmware: Workstation 10 support for Linux. [GH-900]
+* command/build: Added '-parallel' flag so you can disable parallelization
+  with `-no-parallel`. [GH-924]
 
 BUG FIXES:
 

command/build/command.go

@@ -23,12 +23,14 @@ func (Command) Help() string {
 func (c Command) Run(env packer.Environment, args []string) int {
 	var cfgDebug bool
 	var cfgForce bool
+	var cfgParallel bool
 	buildOptions := new(cmdcommon.BuildOptions)
 
 	cmdFlags := flag.NewFlagSet("build", flag.ContinueOnError)
 	cmdFlags.Usage = func() { env.Ui().Say(c.Help()) }
 	cmdFlags.BoolVar(&cfgDebug, "debug", false, "debug mode for builds")
 	cmdFlags.BoolVar(&cfgForce, "force", false, "force a build if artifacts exist")
+	cmdFlags.BoolVar(&cfgParallel, "parallel", true, "enable/disable parallelization")
 	cmdcommon.BuildOptionFlags(cmdFlags, buildOptions)
 	if err := cmdFlags.Parse(args); err != nil {
 		return 1
@@ -176,6 +178,11 @@ func (c Command) Run(env packer.Environment, args []string) int {
 			wg.Wait()
 		}
 
+		if !cfgParallel {
+			log.Printf("Parallelization disabled, waiting for build to finish: %s", b.Name())
+			wg.Wait()
+		}
+
 		if interrupted {
 			log.Println("Interrupted, not going to start any more builds.")
 			break

command/build/help.go

@@ -13,6 +13,7 @@ Options:
   -machine-readable          Machine-readable output
   -except=foo,bar,baz        Build all builds other than these
   -only=foo,bar,baz          Only build the given builds by name
+  -parallel=false            Disable parallelization (on by default)
   -var 'key=value'           Variable for templates, can be used multiple times.
   -var-file=path             JSON file containing user variables.
 `