pkg/stat: sort graph lines

Currently lines in graphs are reordered on each page reload
since use map iteration which is randomized.
This is very inconvinient. Sort lines based on creation order.
This provides stable order and gives a user some control over order.

1 files changed, 22 insertions, 8 deletions

diff --git a/pkg/stat/set.go b/pkg/stat/set.go
index 690d0406a..4bcf2d2c6 100644
--- a/pkg/stat/set.go
+++ b/pkg/stat/set.go
@@ -57,6 +57,7 @@ type set struct {
 	mu           sync.Mutex
 	vals         map[string]*Val
 	graphs       map[string]*graph
+	nextOrder    atomic.Uint64
 	totalTicks   int
 	historySize  int
 	historyTicks int
@@ -71,10 +72,12 @@ type graph struct {
 }
 
 type line struct {
-	desc string
-	rate bool
-	data []float64
-	hist []*gohistogram.NumericHistogram
+	name  string
+	desc  string
+	order uint64
+	rate  bool
+	data  []float64
+	hist  []*gohistogram.NumericHistogram
 }
 
 const (
@@ -187,6 +190,7 @@ func (s *set) New(name, desc string, opts ...any) *Val {
 		name:  name,
 		desc:  desc,
 		graph: name,
+		order: s.nextOrder.Add(1),
 		fmt:   func(v int, period time.Duration) string { return strconv.Itoa(v) },
 	}
 	stacked := false
@@ -245,6 +249,7 @@ type Val struct {
 	link    string
 	graph   string
 	level   Level
+	order   uint64
 	val     atomic.Uint64
 	ext     func() int
 	fmt     func(int, time.Duration) string
@@ -316,8 +321,10 @@ func (s *set) tick() {
 		ln := graph.lines[v.name]
 		if ln == nil {
 			ln = &line{
-				desc: v.desc,
-				rate: v.rate,
+				name:  v.name,
+				desc:  v.desc,
+				order: v.order,
+				rate:  v.rate,
 			}
 			if v.hist {
 				ln.hist = make([]*gohistogram.NumericHistogram, s.historySize)
@@ -405,6 +412,13 @@ func (s *set) RenderHTML() ([]byte, error) {
 		if len(graph.lines) == 0 {
 			continue
 		}
+		var lines []*line
+		for _, ln := range graph.lines {
+			lines = append(lines, ln)
+		}
+		sort.Slice(lines, func(i, j int) bool {
+			return lines[i].order < lines[j].order
+		})
 		g := Graph{
 			ID:      len(graphs),
 			Title:   title,
@@ -415,9 +429,9 @@ func (s *set) RenderHTML() ([]byte, error) {
 		for i := 0; i < s.historyPos; i++ {
 			g.Points[i].X = i * tick
 		}
-		for name, ln := range graph.lines {
+		for _, ln := range lines {
 			if ln.hist == nil {
-				g.Lines = append(g.Lines, name+": "+ln.desc)
+				g.Lines = append(g.Lines, ln.name+": "+ln.desc)
 				for i := 0; i < s.historyPos; i++ {
 					g.Points[i].Y = append(g.Points[i].Y, ln.data[i])
 				}