stop data updating thread when there is no data

common/predicate/predicate.go

@@ -0,0 +1,25 @@
+package predicate
+
+type Predicate func() bool
+
+func All(predicates ...Predicate) Predicate {
+	return func() bool {
+		for _, p := range predicates {
+			if !p() {
+				return false
+			}
+		}
+		return true
+	}
+}
+
+func Any(predicates ...Predicate) Predicate {
+	return func() bool {
+		for _, p := range predicates {
+			if p() {
+				return true
+			}
+		}
+		return false
+	}
+}