From a79b1f057fe10bc2693a12348c48ca1070932d2c Mon Sep 17 00:00:00 2001
From: dmabry <dmabry@sparky.fabe-gray.ts.net>
Date: Fri, 15 May 2026 16:08:12 -0500
Subject: [PATCH] Perf: cache dashboard HTML template at package init
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The dashboard template was parsed on every HTTP request via
template.New().Funcs().Parse() — unnecessary CPU and allocation overhead.

Move template parsing to a package-level variable initialized once at
startup. DashboardHandler now reuses the pre-parsed template.

Also simplified error handling: parse failure logs a warning at init
time and returns an empty template (server still starts); execute
failures log per-request as before.
---
 stats/collector.go | 51 +++++++++++++++++++++++++++-------------------
 1 file changed, 30 insertions(+), 21 deletions(-)

diff --git a/stats/collector.go b/stats/collector.go
index 76bed1b..7572481 100644
--- a/stats/collector.go
+++ b/stats/collector.go
@@ -154,6 +154,35 @@ func (sc *Collector) HistoryHandler(w http.ResponseWriter, r *http.Request) {
 	}
 }
 
+// dashboardTmpl is the pre-parsed dashboard HTML template with custom
+// functions registered. Parsed once at package init and reused for every
+// request to avoid repeated template parsing overhead.
+var dashboardTmpl = func() *template.Template {
+	t, err := template.New("dashboard").Funcs(template.FuncMap{
+		"formatBytes": func(bytes uint64) string {
+			if bytes == 0 {
+				return "0 B"
+			}
+			const unit = 1024
+			const units = "BKMG"
+			i := 0
+			f := float64(bytes)
+			for f >= unit && i < len(units)-1 {
+				f /= unit
+				i++
+			}
+			return fmt.Sprintf("%.1f %sB", f, string(units[i]))
+		},
+	}).Parse(templates.DashboardTpl)
+	if err != nil {
+		log.Printf("[WARN] Failed to parse dashboard template: %v", err)
+		// Return a no-op template so the server still starts;
+		// DashboardHandler will log the nil-template error per-request.
+		return template.New("dashboard")
+	}
+	return t
+}()
+
 // DashboardHandler renders the dashboard HTML page with current stats.
 func (sc *Collector) DashboardHandler(w http.ResponseWriter, r *http.Request) {
 	sc.mu.RLock()
@@ -190,29 +219,9 @@ func (sc *Collector) DashboardHandler(w http.ResponseWriter, r *http.Request) {
 		Uptime:      uptimeStr,
 	}
 
-	t, err := template.New("dashboard").Funcs(template.FuncMap{
-		"formatBytes": func(bytes uint64) string {
-			if bytes == 0 {
-				return "0 B"
-			}
-			const unit = 1024
-			const units = "BKMG"
-			i := 0
-			f := float64(bytes)
-			for f >= unit && i < len(units)-1 {
-				f /= unit
-				i++
-			}
-			return fmt.Sprintf("%.1f %sB", f, string(units[i]))
-		},
-	}).Parse(templates.DashboardTpl)
+	err := dashboardTmpl.Execute(w, d)
 	if err != nil {
 		log.Printf("Web server had issue: %v\n", err)
-	} else {
-		err = t.Execute(w, d)
-		if err != nil {
-			log.Printf("Web server had issue: %v\n", err)
-		}
 	}
 }