Engine: Receiver and Sender preserve Job.Env

When sending a new job to a `engine.Sender`, the corresponding
`engine.Receiver` will receive that job with its environment preserved.
Previously the job name, arguments and streams were preserved but the
env was lost.

Docker-DCO-1.1-Signed-off-by: Solomon Hykes <solomon@docker.com> (github: shykes)

engine/remote.go

@@ -25,7 +25,9 @@ func (s *Sender) Install(eng *Engine) error {
 }
 
 func (s *Sender) Handle(job *Job) Status {
-	msg := data.Empty().Set("cmd", append([]string{job.Name}, job.Args...)...)
+	cmd := append([]string{job.Name}, job.Args...)
+	env := data.Encode(job.Env().MultiMap())
+	msg := data.Empty().Set("cmd", cmd...).Set("env", env)
 	peer, err := beam.SendConn(s, msg.Bytes())
 	if err != nil {
 		return job.Errorf("beamsend: %v", err)
@@ -99,8 +101,15 @@ func (rcv *Receiver) Run() error {
 		}
 		f.Close()
 		defer peer.Close()
-		cmd := data.Message(p).Get("cmd")
+		msg := data.Message(p)
+		cmd := msg.Get("cmd")
 		job := rcv.Engine.Job(cmd[0], cmd[1:]...)
+		// Decode env
+		env, err := data.Decode(msg.GetOne("env"))
+		if err != nil {
+			return fmt.Errorf("error decoding 'env': %v", err)
+		}
+		job.Env().InitMultiMap(env)
 		stdout, err := beam.SendRPipe(peer, data.Empty().Set("cmd", "log", "stdout").Bytes())
 		if err != nil {
 			return err

engine/remote_test.go

@@ -82,6 +82,47 @@ func TestStdin(t *testing.T) {
 	)
 }
 
+func TestEnv(t *testing.T) {
+	var (
+		foo          string
+		answer       int
+		shadok_words []string
+	)
+	testRemote(t,
+
+		func(eng *Engine) {
+			job := eng.Job("sendenv")
+			job.Env().Set("foo", "bar")
+			job.Env().SetInt("answer", 42)
+			job.Env().SetList("shadok_words", []string{"ga", "bu", "zo", "meu"})
+			if err := job.Run(); err != nil {
+				t.Fatal(err)
+			}
+		},
+
+		func(eng *Engine) {
+			eng.Register("sendenv", func(job *Job) Status {
+				foo = job.Env().Get("foo")
+				answer = job.Env().GetInt("answer")
+				shadok_words = job.Env().GetList("shadok_words")
+				return StatusOK
+			})
+		},
+	)
+	// Check for results here rather than inside the job handler,
+	// otherwise the tests may incorrectly pass if the handler is not
+	// called.
+	if foo != "bar" {
+		t.Fatalf("%#v", foo)
+	}
+	if answer != 42 {
+		t.Fatalf("%#v", answer)
+	}
+	if strings.Join(shadok_words, ", ") != "ga, bu, zo, meu" {
+		t.Fatalf("%#v", shadok_words)
+	}
+}
+
 // Helpers
 
 func testRemote(t *testing.T, senderSide, receiverSide func(*Engine)) {