traversal: fix race in interface metrics step

Author: lebauce

cmd/allinone/allinone.go

@@ -134,7 +134,7 @@ var AllInOneCmd = &cobra.Command{
 
 		os.Setenv("SKYDIVE_ANALYZERS", fmt.Sprintf("%s:%d", addr, svcAddr.Port))
 		os.Setenv("SKYDIVE_LOGGING_FILE_PATH", logFile+"-agent"+extension)
-		
+
 		agentAttr := &os.ProcAttr{
 			Files: []*os.File{os.Stdin, os.Stdout, os.Stderr},
 			Env:   os.Environ(),

graffiti/graph/traversal/traversal.go

@@ -890,7 +890,9 @@ func (tv *GraphTraversalV) Sort(ctx StepContext, keys ...interface{}) *GraphTrav
 		sortBy = defaultSortBy
 	}
 
+	tv.GraphTraversal.RLock()
 	graph.SortNodes(tv.nodes, sortBy, sortOrder)
+	tv.GraphTraversal.RUnlock()
 
 	return tv
 }

gremlin/traversal/topology.go

@@ -39,20 +39,19 @@ func InterfaceMetrics(ctx traversal.StepContext, tv *traversal.GraphTraversalV,
 	}
 
 	startField := key + ".Start"
-
 	tv = tv.Dedup(ctx, "ID", startField).Sort(ctx, common.SortAscending, startField)
 
 	if tv.Error() != nil {
 		return NewMetricsTraversalStepFromError(tv.Error())
 	}
 
+	tv.GraphTraversal.RLock()
+	defer tv.GraphTraversal.RUnlock()
+
 	metrics := make(map[string][]common.Metric)
 	it := ctx.PaginationRange.Iterator()
 	gslice := tv.GraphTraversal.Graph.GetContext().TimeSlice
 
-	tv.GraphTraversal.RLock()
-	defer tv.GraphTraversal.RUnlock()
-
 nodeloop:
 	for _, n := range tv.GetNodes() {
 		if it.Done() {