From 916f2a7b8c117befcb4eeaa32b8ed9ec8ff1f96f Mon Sep 17 00:00:00 2001
From: Armon Dadgar <armon.dadgar@gmail.com>
Date: Mon, 7 Sep 2015 12:25:23 -0700
Subject: [PATCH] scheduler: util method to diff task groups

---
 scheduler/util.go      | 25 +++++++++++++++++++++++++
 scheduler/util_test.go | 33 +++++++++++++++++++++++++++++++++
 2 files changed, 58 insertions(+)

diff --git a/scheduler/util.go b/scheduler/util.go
index 2911b9503..7f8278ba4 100644
--- a/scheduler/util.go
+++ b/scheduler/util.go
@@ -3,6 +3,7 @@ package scheduler
 import (
 	"fmt"
 	"math/rand"
+	"reflect"
 
 	"github.com/hashicorp/nomad/nomad/structs"
 )
@@ -205,3 +206,27 @@ func shuffleNodes(nodes []*structs.Node) {
 		nodes[i], nodes[j] = nodes[j], nodes[i]
 	}
 }
+
+// tasksUpdated does a diff between task groups to see if the
+// tasks, their drivers or config have updated.
+func tasksUpdated(a, b *structs.TaskGroup) bool {
+	// If the number of tasks do not match, clearly there is an update
+	if len(a.Tasks) != len(b.Tasks) {
+		return true
+	}
+
+	// Check each task
+	for _, at := range a.Tasks {
+		bt := b.LookupTask(at.Name)
+		if bt == nil {
+			return true
+		}
+		if at.Driver != bt.Driver {
+			return true
+		}
+		if !reflect.DeepEqual(at.Config, bt.Config) {
+			return true
+		}
+	}
+	return false
+}
diff --git a/scheduler/util_test.go b/scheduler/util_test.go
index a19186fe2..53fada5f9 100644
--- a/scheduler/util_test.go
+++ b/scheduler/util_test.go
@@ -227,3 +227,36 @@ func TestShuffleNodes(t *testing.T) {
 		t.Fatalf("shoudl not match")
 	}
 }
+
+func TestTasksUpdated(t *testing.T) {
+	j1 := mock.Job()
+	j2 := mock.Job()
+
+	if tasksUpdated(j1.TaskGroups[0], j2.TaskGroups[0]) {
+		t.Fatalf("bad")
+	}
+
+	j2.TaskGroups[0].Tasks[0].Config["command"] = "/bin/other"
+	if !tasksUpdated(j1.TaskGroups[0], j2.TaskGroups[0]) {
+		t.Fatalf("bad")
+	}
+
+	j3 := mock.Job()
+	j3.TaskGroups[0].Tasks[0].Name = "foo"
+	if !tasksUpdated(j1.TaskGroups[0], j3.TaskGroups[0]) {
+		t.Fatalf("bad")
+	}
+
+	j4 := mock.Job()
+	j4.TaskGroups[0].Tasks[0].Driver = "foo"
+	if !tasksUpdated(j1.TaskGroups[0], j4.TaskGroups[0]) {
+		t.Fatalf("bad")
+	}
+
+	j5 := mock.Job()
+	j5.TaskGroups[0].Tasks = append(j5.TaskGroups[0].Tasks,
+		j5.TaskGroups[0].Tasks[0])
+	if !tasksUpdated(j1.TaskGroups[0], j5.TaskGroups[0]) {
+		t.Fatalf("bad")
+	}
+}