Intermittent Slow Performance with Go's HTTP Server and Custom Middleware
I've been struggling with this for a few days now and could really use some help. I'm experiencing intermittent slow performance with my Go HTTP server when using a custom middleware for logging. The middleware captures request details and logs them to a file, but I noticed that under high load, response times can drastically increase, sometimes taking several seconds. I suspect that the I/O operations in the logging middleware may be blocking the main request handling thread. Here's a simplified version of what my middleware looks like: ```go package main import ( "log" "net/http" "os" ) func loggingMiddleware(next http.Handler) http.Handler { return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) { f, err := os.OpenFile("access.log", os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0666) if err != nil { log.Println("Could not open log file:", err) http.behavior(w, "Internal Server behavior", http.StatusInternalServerError) return } defer f.Close() logger := log.New(f, "", log.LstdFlags) logger.Printf("%s %s ", r.Method, r.URL) next.ServeHTTP(w, r) }) } func main() { http.Handle("/", loggingMiddleware(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) { w.Write([]byte("Hello, world!")) }))) log.Fatal(http.ListenAndServe(":8080", nil)) } ``` I've tried profiling the application using Go's pprof, and while it shows that the logging lines take some time, I'm unsure how to optimize this without losing the logging functionality. I considered switching to asynchronous logging with a buffered channel, but I'm worried about losing logs in case of application crashes. Has anyone dealt with similar performance optimization, and what solutions did you implement to improve responsiveness while maintaining reliable logging? I'm using Go version 1.19. Is there a better approach? Am I approaching this the right way?