Add a function to convert the running configuration to JSON.

gnmi/server.go

@@ -296,6 +296,17 @@ func (s *Server) toGoStruct(jsonTree map[string]interface{}) (ygot.ValidatedGoSt
 	return goStruct, nil
 }
 
+// ConfigAsJSON takes the current configuration of the running server and
+// returns it in a RFC7951 compliant json string.
+func (s *Server) ConfigAsJSON() (string, error) {
+	return ygot.EmitJSON(s.config, &ygot.EmitJSONConfig{
+		Format: ygot.RFC7951,
+		RFC7951Config: &ygot.RFC7951JSONConfig{
+			AppendModuleName: true,
+		},
+	})
+}
+
 // getGNMIServiceVersion returns a pointer to the gNMI service version string.
 // The method is non-trivial because of the way it is defined in the proto file.
 func getGNMIServiceVersion() (*string, error) {

gnmi/server_test.go

@@ -1696,3 +1696,64 @@ func updateLess(a, b *pb.Update) bool {
 	}
 	return pathA < pathB
 }
+
+// jsonBytesEqual is a helper function to compare two json strings for
+// equality.
+func jsonBytesEqual(a, b []byte) (bool, error) {
+	var j, j2 interface{}
+	if err := json.Unmarshal(a, &j); err != nil {
+		return false, err
+	}
+	if err := json.Unmarshal(b, &j2); err != nil {
+		return false, err
+	}
+	return reflect.DeepEqual(j2, j), nil
+}
+
+// TestConfigAsJSON validates that the method `ConfigAsJSON` returns a json
+// string that meets the running configuration of the server in a fashion that
+// can be loaded back into the server.
+func TestConfigToJSON(t *testing.T) {
+        jsonConfigRoot := `{
+          "openconfig-system:system": {
+            "openconfig-openflow:openflow": {
+              "agent": {
+                "config": {
+                  "failure-mode": "SECURE",
+                  "max-backoff": 10
+                }
+              }
+            }
+          },
+          "openconfig-platform:components": {
+            "component": [
+              {
+                "config": {
+                  "name": "swpri1-1-1"
+                },
+                "name": "swpri1-1-1"
+              }
+            ]
+          }
+        }`
+
+	s, err := NewServer(model, []byte(jsonConfigRoot), nil)
+	if err != nil {
+		t.Fatalf("error in creating server: %v", err)
+	}
+
+	res, err := s.ConfigAsJSON()
+	if err != nil {
+		t.Fatalf("error in creating json from model: %v", err)
+	}
+
+	areEqual, err := jsonBytesEqual([]byte(jsonConfigRoot), []byte(res))
+	if err != nil {
+		t.Fatalf("error in comparing json bytes: %v", err)
+	}
+
+	if (!areEqual) {
+		t.Errorf("config mismatch!\n Got: %s\n Wanted: %s", res, jsonConfigRoot)
+	}
+
+}

gnmi_target/gnmi_target.go

@@ -22,7 +22,9 @@ import (
 	"io/ioutil"
 	"net"
 	"os"
+	"os/signal"
 	"reflect"
+	"syscall"
 
 	log "github.com/golang/glog"
 	"golang.org/x/net/context"
@@ -43,6 +45,7 @@ import (
 var (
 	bindAddr   = flag.String("bind_address", ":9339", "Bind to address:port or just :port")
 	configFile = flag.String("config", "", "IETF JSON file for target startup config")
+	saveOnExit = flag.Bool("save_on_exit", false, "Save the config before exiting the server.")
 )
 
 type server struct {
@@ -79,7 +82,7 @@ func (s *server) Set(ctx context.Context, req *pb.SetRequest) (*pb.SetResponse,
 	return s.Server.Set(ctx, req)
 }
 
-// Set overrides the Subscribe func of gnmi.Target to provide user auth.
+// Subscribe overrides the Subscribe func of gnmi.Target to provide user auth.
 func (s *server) Subscribe(stream pb.GNMI_SubscribeServer) error {
 	msg, ok := credentials.AuthorizeUser(stream.Context())
 	if !ok {
@@ -90,6 +93,24 @@ func (s *server) Subscribe(stream pb.GNMI_SubscribeServer) error {
 	return s.Server.Subscribe(stream)
 }
 
+// shutdownHook saves the running config back out to the config file.
+func (s *server) shutdownHook (c chan os.Signal) {
+	sig := <- c
+	log.Infof("Gracefully stopping: %s", sig)
+	cfg, err := s.ConfigAsJSON()
+	if err != nil {
+		log.Exitf("Error getting json representation from server: %v", err)
+	}
+	if *configFile != "" {
+		err := os.WriteFile(*configFile, []byte(cfg), 0644)
+		if err != nil {
+			log.Exitf("error in writing config file: %v", err)
+		}
+	}
+	log.Infof("Config saved back out to file.")
+	os.Exit(0)
+}
+
 func main() {
 	model := gnmi.NewModel(modeldata.ModelData,
 		reflect.TypeOf((*gostruct.Device)(nil)),
@@ -134,6 +155,12 @@ func main() {
 		log.Exitf("failed to listen: %v", err)
 	}
 
+	if(*saveOnExit) {
+		c := make(chan os.Signal, 1)
+		signal.Notify(c, syscall.SIGINT, syscall.SIGTERM)
+		go s.shutdownHook(c)
+	}
+
 	log.Info("starting to serve")
 	if err := g.Serve(listen); err != nil {
 		log.Exitf("failed to serve: %v", err)