Add on-demand pprof profiling grouped by route

Expose pprof at /debug/pprof via -pprof flag, tag each handler with runtime/pprof route label, add handleRoute helper to avoid repeating patterns, and document UI workflow in README.

1 files changed, 43 insertions, 8 deletions

diff --git a/web/server.go b/web/server.go
index 198cb44..26dbb06 100644
--- a/web/server.go
+++ b/web/server.go
@@ -1,8 +1,11 @@
 package web
 
 import (
+	"context"
 	"database/sql"
 	"net/http"
+	http_pprof "net/http/pprof"
+	runtime_pprof "runtime/pprof"
 	"sync"
 	"time"
 
@@ -21,6 +24,7 @@ type Server struct {
 	returnToURL string
 	syncMu      sync.Mutex
 	syncActive  bool
+	enablePprof bool
 }
 
 type syncClient interface {
@@ -32,20 +36,51 @@ func NewServer(db *sql.DB, configPath string) *Server {
 	return &Server{db: db, configPath: configPath}
 }
 
+func (s *Server) WithPprof(enabled bool) *Server {
+	s.enablePprof = enabled
+	return s
+}
+
 func (s *Server) Handler() http.Handler {
 	mux := http.NewServeMux()
 	mux.Handle("GET /static/", http.FileServer(http.FS(staticFiles)))
-	mux.HandleFunc("GET /", s.handleRides)
-	mux.HandleFunc("GET /rides/{id}", s.handleRide)
-	mux.HandleFunc("GET /analytics", s.handleAnalytics)
-	mux.HandleFunc("POST /rides/{id}/official-climbs", s.handleCreateOfficialClimb)
-	mux.HandleFunc("GET /sync", s.handleSyncForm)
-	mux.HandleFunc("POST /sync", s.handleSync)
-	mux.HandleFunc("GET /strava/login", s.handleStravaLogin)
-	mux.HandleFunc("GET /strava/callback", s.handleStravaCallback)
+	handleRoute(mux, "GET /", s.handleRides)
+	handleRoute(mux, "GET /rides/{id}", s.handleRide)
+	handleRoute(mux, "GET /analytics", s.handleAnalytics)
+	handleRoute(mux, "POST /rides/{id}/official-climbs", s.handleCreateOfficialClimb)
+	handleRoute(mux, "GET /sync", s.handleSyncForm)
+	handleRoute(mux, "POST /sync", s.handleSync)
+	handleRoute(mux, "GET /strava/login", s.handleStravaLogin)
+	handleRoute(mux, "GET /strava/callback", s.handleStravaCallback)
+	if s.enablePprof {
+		registerPprof(mux)
+	}
 	return kcore.RecoverMiddleware(mux)
 }
 
+func handleRoute(mux *http.ServeMux, pattern string, handler http.HandlerFunc) {
+	mux.HandleFunc(pattern, withPprofLabel(pattern, handler))
+}
+
+func withPprofLabel(route string, next http.HandlerFunc) http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		runtime_pprof.Do(r.Context(), runtime_pprof.Labels("route", route), func(ctx context.Context) {
+			next(w, r.WithContext(ctx))
+		})
+	}
+}
+
+func registerPprof(mux *http.ServeMux) {
+	mux.HandleFunc("GET /debug/pprof/", http_pprof.Index)
+	mux.HandleFunc("GET /debug/pprof/cmdline", http_pprof.Cmdline)
+	mux.HandleFunc("GET /debug/pprof/profile", http_pprof.Profile)
+	mux.HandleFunc("GET /debug/pprof/symbol", http_pprof.Symbol)
+	mux.HandleFunc("GET /debug/pprof/trace", http_pprof.Trace)
+	for _, name := range []string{"allocs", "block", "goroutine", "heap", "mutex", "threadcreate"} {
+		mux.Handle("GET /debug/pprof/"+name, http_pprof.Handler(name))
+	}
+}
+
 func (s *Server) ListenAndServe(addr string) error {
 	return http.ListenAndServe(addr, s.Handler())
 }