packer/rpc: Properly support hooks

builder/amazonebs/builder.go

@@ -60,6 +60,9 @@ func (b *Builder) Run(ui packer.Ui, hook packer.Hook) {
 		MaxCount:     0,
 	}
 
+	hook.Run(HookPreLaunch, nil, ui)
+	return
+
 	ui.Say("Launching a source AWS instance...\n")
 	runResp, err := ec2conn.RunInstances(runOpts)
 	if err != nil {

builder/amazonebs/hook.go

@@ -0,0 +1,4 @@
+package amazonebs
+
+// This hook is fired prior to launching the EC2 instance.
+const HookPreLaunch = "amazonebs_pre_launch"

config.go

@@ -90,3 +90,8 @@ func (c *config) LoadCommand(name string) (packer.Command, error) {
 
 	return plugin.Command(exec.Command(commandBin))
 }
+
+func (c *config) LoadHook(name string) (packer.Hook, error) {
+	log.Printf("Loading hook: %s\n", name)
+	return plugin.Hook(exec.Command(name))
+}

packer.go

@@ -87,6 +87,7 @@ func main() {
 	envConfig.Commands = config.CommandNames()
 	envConfig.Components.Builder = config.LoadBuilder
 	envConfig.Components.Command = config.LoadCommand
+	envConfig.Components.Hook = config.LoadHook
 
 	env, err := packer.NewEnvironment(envConfig)
 	if err != nil {

packer/rpc/environment.go

@@ -50,13 +50,12 @@ func (e *Environment) Hook(name string) (h packer.Hook, err error) {
 		return
 	}
 
-	_, err = rpc.Dial("tcp", reply)
+	client, err := rpc.Dial("tcp", reply)
 	if err != nil {
 		return
 	}
 
-	// TODO: Hook
-	h = nil
+	h = Hook(client)
 	return
 }
 
@@ -89,14 +88,14 @@ func (e *EnvironmentServer) Cli(args *EnvironmentCliArgs, reply *int) (err error
 }
 
 func (e *EnvironmentServer) Hook(name *string, reply *string) error {
-	_, err := e.env.Hook(*name)
+	hook, err := e.env.Hook(*name)
 	if err != nil {
 		return err
 	}
 
 	// Wrap it
-	// TODO: Register hook
 	server := rpc.NewServer()
+	RegisterHook(server, hook)
 
 	*reply = serveSingleConn(server)
 	return nil