engine: graph: Add a function for printing Send/Recv logs

engine/graph/actions.go

@@ -124,6 +124,9 @@ func (obj *Engine) Process(ctx context.Context, vertex pgraph.Vertex) error {
 		if updated, err := SendRecv(res); err != nil {
 			return errwrap.Wrapf(err, "could not SendRecv")
 		} else if len(updated) > 0 {
+			//for _, s := range graph.UpdatedStrings(updated) {
+			//	obj.Logf("SendRecv: %s", s)
+			//}
 			for r, m := range updated { // map[engine.RecvableRes]map[string]*engine.Send
 				v, ok := r.(pgraph.Vertex)
 				if !ok {

engine/graph/sendrecv.go

@@ -243,3 +243,19 @@ func TypeCmp(a, b reflect.Value) error {
 
 	return nil // identical Type()'s
 }
+
+// UpdatedStrings returns a list of strings showing what was updated after a
+// Send/Recv run returned the updated datastructure. This is useful for logs.
+func UpdatedStrings(updated map[engine.RecvableRes]map[string]*engine.Send) []string {
+	out := []string{}
+	for r, m := range updated { // map[engine.RecvableRes]map[string]*engine.Send
+		for s, send := range m {
+			if !send.Changed {
+				continue
+			}
+			x := fmt.Sprintf("%v.%s -> %v.%s", send.Res, send.Key, r, s)
+			out = append(out, x)
+		}
+	}
+	return out
+}