Add logging and recover from panic

sonic_data_client/db_client.go

@@ -721,6 +721,12 @@ func makeJSON_redis(msi *map[string]interface{}, key *string, op *string, mfv ma
 // emitJSON marshalls map[string]interface{} to JSON byte stream.
 func emitJSON(v *map[string]interface{}) ([]byte, error) {
 	//j, err := json.MarshalIndent(*v, "", indentString)
+	defer func() {
+		if r := recover(); r != nil {
+			log.V(2).Infof("Recovered from panic", r)
+			log.V(2).Infof("Current state of map to be serialized is: ", *v)
+		}
+	}
 	j, err := json.Marshal(*v)
 	if err != nil {
 		return nil, fmt.Errorf("JSON marshalling error: %v", err)
@@ -759,9 +765,13 @@ func TableData2Msi(tblPath *tablePath, useKey bool, op *string, msi *map[string]
 		dbkeys = []string{tblPath.tableName + tblPath.delimitor + tblPath.tableKey}
 	}
 
+	log.V(4).Infof("dbkeys to be pulled from redis %v", dbkeys)
+	log.V(4).Infof("State of map before adding redis data %v", msi)
+
 	// Asked to use jsonField and jsonTableKey in the final json value
 	if tblPath.jsonField != "" && tblPath.jsonTableKey != "" {
 		val, err := redisDb.HGet(dbkeys[0], tblPath.field).Result()
+		log.V(4).Infof("Data pulled for key %s and field %s: %s", dbkeys[0], tblPath.field, val)
 		if err != nil {
 			log.V(3).Infof("redis HGet failed for %v %v", tblPath, err)
 			// ignore non-existing field which was derived from virtual path
@@ -779,7 +789,7 @@ func TableData2Msi(tblPath *tablePath, useKey bool, op *string, msi *map[string]
 			log.V(2).Infof("redis HGetAll failed for  %v, dbkey %s", tblPath, dbkey)
 			return err
 		}
-
+		log.V(4).Infof("Data pulled for dbkey %s: %v", dbkey, fv)
 		if tblPath.jsonTableKey != "" { // If jsonTableKey was prepared, use it
 			err = makeJSON_redis(msi, &tblPath.jsonTableKey, op, fv)
 		} else if (tblPath.tableKey != "" && !useKey) || tblPath.tableName == dbkey {
@@ -800,6 +810,7 @@ func TableData2Msi(tblPath *tablePath, useKey bool, op *string, msi *map[string]
 		}
 		log.V(6).Infof("Added idex %v fv %v ", idx, fv)
 	}
+	log.V(4).Infof("State of map after adding redis data %v", *msi)
 	return nil
 }
 
@@ -839,6 +850,7 @@ func tableData2TypedValue(tblPaths []tablePath, op *string) (*gnmipb.TypedValue,
 					log.V(2).Infof("redis HGet failed for %v", tblPath)
 					return nil, err
 				}
+				log.V(4).Infof("Data pulled for key %s and field %s: %s", key, tblPath.field, val)
 				// TODO: support multiple table paths
 				return &gnmipb.TypedValue{
 					Value: &gnmipb.TypedValue_StringVal{