Allow count 0 on system jobs

nomad/structs/structs.go

@@ -1080,9 +1080,9 @@ func (j *Job) Validate() error {
 			taskGroups[tg.Name] = idx
 		}
 
-		if j.Type == "system" && tg.Count != 1 {
+		if j.Type == "system" && tg.Count > 1 {
 			mErr.Errors = append(mErr.Errors,
-				fmt.Errorf("Job task group %d has count %d. Only count of 1 is supported with system scheduler",
+				fmt.Errorf("Job task group %d has count %d. Count cannot exceed 1 with system scheduler",
 					idx+1, tg.Count))
 		}
 	}
@@ -1096,7 +1096,7 @@ func (j *Job) Validate() error {
 	}
 
 	// Validate periodic is only used with batch jobs.
-	if j.IsPeriodic() {
+	if j.IsPeriodic() && j.Periodic.Enabled {
 		if j.Type != JobTypeBatch {
 			mErr.Errors = append(mErr.Errors,
 				fmt.Errorf("Periodic can only be used with %q scheduler", JobTypeBatch))

nomad/structs/structs_test.go

@@ -117,6 +117,7 @@ func testJob() *Job {
 				Name:  "web",
 				Count: 10,
 				RestartPolicy: &RestartPolicy{
+					Mode:     RestartPolicyModeFail,
 					Attempts: 3,
 					Interval: 10 * time.Minute,
 					Delay:    1 * time.Minute,
@@ -145,13 +146,18 @@ func testJob() *Job {
 						Resources: &Resources{
 							CPU:      500,
 							MemoryMB: 256,
+							DiskMB:   20,
 							Networks: []*NetworkResource{
 								&NetworkResource{
 									MBits:        50,
 									DynamicPorts: []Port{{Label: "http"}},
 								},
 							},
 						},
+						LogConfig: &LogConfig{
+							MaxFiles:      10,
+							MaxFileSizeMB: 1,
+						},
 					},
 				},
 				Meta: map[string]string{
@@ -194,6 +200,27 @@ func TestJob_IsPeriodic(t *testing.T) {
 	}
 }
 
+func TestJob_SystemJob_Validate(t *testing.T) {
+	j := testJob()
+	j.Type = JobTypeSystem
+	j.InitFields()
+
+	err := j.Validate()
+	if err == nil || !strings.Contains(err.Error(), "exceed") {
+		t.Fatalf("expect error due to count")
+	}
+
+	j.TaskGroups[0].Count = 0
+	if err := j.Validate(); err != nil {
+		t.Fatalf("unexpected err: %v", err)
+	}
+
+	j.TaskGroups[0].Count = 1
+	if err := j.Validate(); err != nil {
+		t.Fatalf("unexpected err: %v", err)
+	}
+}
+
 func TestTaskGroup_Validate(t *testing.T) {
 	tg := &TaskGroup{
 		Count: -1,