Tantas · September 8, 2021 18:22 · Apr 5, 2015 · Apr 5, 2015 · Oct 31, 2012 · Oct 31, 2012
diff --git a/main.go b/main.go
@@ -1,7 +1,25 @@
 func main() {
+	// Open appending or create the access log.
+	accessLogFile, err := os.OpenFile("access.log", os.O_RDWR|os.O_APPEND|os.O_CREATE, 0666)
+	if err != nil {
+		log.Fatalf("Error using assess.log: %s", err.Error())
+	}
+	defer accessLogFile.Close()
+
+	// Create a buffered writer and ensure it is flushed when an interrupt occurs.
+	bufferedAccessLogWriter := bufio.NewWriter(accessLogFile)
+	c := make(chan os.Signal, 1)
+	signal.Notify(c, os.Interrupt)
+	go func() {
+		<-c
+		log.Println("Flushing logs and exiting...")
+		bufferedAccessLogWriter.Flush()
+		os.Exit(0)
+	}()
+
 	mux := http.DefaultServeMux
 	mux.HandleFunc("/", indexHandler)
-	loggingHandler := NewApacheLoggingHandler(mux, os.Stderr)
+	loggingHandler := NewApacheLoggingHandler(mux, bufferedAccessLogWriter)
 	server := &http.Server{
 		Addr:    ":8000",
 		Handler: loggingHandler,

diff --git a/log.go b/log.go
@@ -1,3 +1,14 @@
+import (
+	"fmt"
+	"io"
+	"net/http"
+	"strings"
+	"time"
+)
+
+// https://httpd.apache.org/docs/2.2/logs.html#combined + execution time.
+const apacheFormatPattern = "%s - - [%s] \"%s %s %s\" %d %d \"%s\" \"%s\" %.4f\n"
+
 type ApacheLogRecord struct {
 	http.ResponseWriter
 
@@ -6,13 +17,15 @@ type ApacheLogRecord struct {
 	method, uri, protocol string
 	status                int
 	responseBytes         int64
+	referer               string
+	userAgent             string
 	elapsedTime           time.Duration
 }
 
 func (r *ApacheLogRecord) Log(out io.Writer) {
 	timeFormatted := r.time.Format("02/Jan/2006 03:04:05")
-	requestLine := fmt.Sprintf("%s %s %s", r.method, r.uri, r.protocol)
-	fmt.Fprintf(out, ApacheFormatPattern, r.ip, timeFormatted, requestLine, r.status, r.responseBytes,
+	fmt.Fprintf(out, apacheFormatPattern, r.ip, timeFormatted, r.method,
+		r.uri, r.protocol, r.status, r.responseBytes, r.referer, r.userAgent,
 		r.elapsedTime.Seconds())
 }
 
@@ -45,6 +58,16 @@ func (h *ApacheLoggingHandler) ServeHTTP(rw http.ResponseWriter, r *http.Request
 		clientIP = clientIP[:colon]
 	}
 
+	referer := r.Referer()
+	if referer == "" {
+		referer = "-"
+	}
+
+	userAgent := r.UserAgent()
+	if userAgent == "" {
+		userAgent = "-"
+	}
+
 	record := &ApacheLogRecord{
 		ResponseWriter: rw,
 		ip:             clientIP,
@@ -53,6 +76,8 @@ func (h *ApacheLoggingHandler) ServeHTTP(rw http.ResponseWriter, r *http.Request
 		uri:            r.RequestURI,
 		protocol:       r.Proto,
 		status:         http.StatusOK,
+		referer:        referer,
+		userAgent:      userAgent,
 		elapsedTime:    time.Duration(0),
 	}
 

diff --git a/main.go b/main.go
@@ -3,8 +3,8 @@ func main() {
 	mux.HandleFunc("/", indexHandler)
 	loggingHandler := NewApacheLoggingHandler(mux, os.Stderr)
 	server := &http.Server{
-		Addr:    fmt.Sprintf(":%s", 2345),
+		Addr:    ":8000",
 		Handler: loggingHandler,
 	}
 	server.ListenAndServe()
-}
+}
diff --git a/main.go b/main.go
@@ -0,0 +1,10 @@
+func main() {
+	mux := http.DefaultServeMux
+	mux.HandleFunc("/", indexHandler)
+	loggingHandler := NewApacheLoggingHandler(mux, os.Stderr)
+	server := &http.Server{
+		Addr:    fmt.Sprintf(":%s", 2345),
+		Handler: loggingHandler,
+	}
+	server.ListenAndServe()
+}
diff --git a/log.go b/log.go
@@ -0,0 +1,67 @@
+type ApacheLogRecord struct {
+	http.ResponseWriter
+
+	ip                    string
+	time                  time.Time
+	method, uri, protocol string
+	status                int
+	responseBytes         int64
+	elapsedTime           time.Duration
+}
+
+func (r *ApacheLogRecord) Log(out io.Writer) {
+	timeFormatted := r.time.Format("02/Jan/2006 03:04:05")
+	requestLine := fmt.Sprintf("%s %s %s", r.method, r.uri, r.protocol)
+	fmt.Fprintf(out, ApacheFormatPattern, r.ip, timeFormatted, requestLine, r.status, r.responseBytes,
+		r.elapsedTime.Seconds())
+}
+
+func (r *ApacheLogRecord) Write(p []byte) (int, error) {
+	written, err := r.ResponseWriter.Write(p)
+	r.responseBytes += int64(written)
+	return written, err
+}
+
+func (r *ApacheLogRecord) WriteHeader(status int) {
+	r.status = status
+	r.ResponseWriter.WriteHeader(status)
+}
+
+type ApacheLoggingHandler struct {
+	handler http.Handler
+	out     io.Writer
+}
+
+func NewApacheLoggingHandler(handler http.Handler, out io.Writer) http.Handler {
+	return &ApacheLoggingHandler{
+		handler: handler,
+		out:     out,
+	}
+}
+
+func (h *ApacheLoggingHandler) ServeHTTP(rw http.ResponseWriter, r *http.Request) {
+	clientIP := r.RemoteAddr
+	if colon := strings.LastIndex(clientIP, ":"); colon != -1 {
+		clientIP = clientIP[:colon]
+	}
+
+	record := &ApacheLogRecord{
+		ResponseWriter: rw,
+		ip:             clientIP,
+		time:           time.Time{},
+		method:         r.Method,
+		uri:            r.RequestURI,
+		protocol:       r.Proto,
+		status:         http.StatusOK,
+		elapsedTime:    time.Duration(0),
+	}
+
+	startTime := time.Now()
+	h.handler.ServeHTTP(record, r)
+	finishTime := time.Now()
+
+	record.time = finishTime.UTC()
+	record.elapsedTime = finishTime.Sub(startTime)
+
+	record.Log(h.out)
+}