Add topology.ReplaceNode() for efficiency (#3073)

* Add topology.ReplaceNode() for efficiency

In some places AddNode() was called after adding to an existing node,
in which case the Merge() is just a waste of time.

probe/host/tagger.go

@@ -33,7 +33,7 @@ func (t Tagger) Tag(r report.Report) (report.Report, error) {
 	// and as such do their own host tagging.
 	for _, topology := range []report.Topology{r.Process, r.Container, r.ContainerImage, r.Host, r.Pod} {
 		for _, node := range topology.Nodes {
-			topology.AddNode(node.WithLatests(metadata).WithParents(parents))
+			topology.ReplaceNode(node.WithLatests(metadata).WithParents(parents))
 		}
 	}
 	return r, nil

probe/topology_tagger.go

@@ -18,7 +18,7 @@ func (topologyTagger) Name() string { return "Topology" }
 func (topologyTagger) Tag(r report.Report) (report.Report, error) {
 	r.WalkNamedTopologies(func(name string, t *report.Topology) {
 		for _, node := range t.Nodes {
-			t.AddNode(node.WithTopology(name))
+			t.ReplaceNode(node.WithTopology(name))
 		}
 	})
 	return r, nil

report/topology.go

@@ -111,6 +111,13 @@ func (t Topology) AddNode(node Node) {
 	t.Nodes[node.ID] = node
 }
 
+// ReplaceNode adds node to the topology under key nodeID; if a
+// node already exists for this key, node replaces that node.
+// Like AddNode, it mutates the Topology
+func (t Topology) ReplaceNode(node Node) {
+	t.Nodes[node.ID] = node
+}
+
 // GetShape returns the current topology shape, or the default if there isn't one.
 func (t Topology) GetShape() string {
 	if t.Shape == "" {