accesslog middleware: more examples and usecase, e.g. log latency per handler and sessions values or authentication

relative to: #1601

_examples/logging/request-logger/accesslog/access.log.sample

@@ -4,3 +4,6 @@
 2020-09-08 13:41:26|0s|GET|/public||404|765 B|83 B|||
 2020-09-08 13:41:36|0s|GET|/user/kataras|username=kataras|200|771 B|91 B||Hello, kataras!|
 2020-09-08 13:41:47|0s|GET|/user/kataras|username=kataras a_query_parameter=name|200|774 B|91 B||Hello, kataras!|
+2020-09-08 20:37:33|0s|GET|/admin|auth=admin:admin|200|608 B|164 B||<h2>Username: admin</h2><h3>Password: admin</h3>|
+2020-09-09 07:56:00|738.1µs|GET|/session|session_id=23fe763f-c9d5-4d65-9e1a-2cc8d23d1aa3 session_test_key=session_test_value|200|818 B|302 B||OK|
+2020-09-09 08:19:13|2.0053069s|GET|/fields|fieldsHandler_latency=2s|200|570 B|130 B||OK|

_examples/logging/request-logger/accesslog/main.go

@@ -5,11 +5,15 @@ import (
 
 	"github.com/kataras/iris/v12"
 	"github.com/kataras/iris/v12/middleware/accesslog"
+	"github.com/kataras/iris/v12/middleware/basicauth"
+	"github.com/kataras/iris/v12/middleware/requestid"
+	"github.com/kataras/iris/v12/sessions"
 
 	rotatelogs "github.com/lestrrat-go/file-rotatelogs"
 )
 
-func main() {
+func makeAccessLog() *accesslog.AccessLog {
+	// Optionally, let's Go with log rotation.
 	pathToAccessLog := "./access_log.%Y%m%d%H%M"
 	w, err := rotatelogs.New(
 		pathToAccessLog,
@@ -18,9 +22,36 @@ func main() {
 	if err != nil {
 		panic(err)
 	}
+
+	// Initialize a new access log middleware.
+	// Accepts an `io.Writer`.
 	ac := accesslog.New(w)
 	ac.TimeFormat = "2006-01-02 15:04:05"
 
+	// Example of adding more than one field to the logger.
+	// Here we logging all the session values this request has.
+	//
+	// You can also add fields per request handler,
+	// look below to the `fieldsHandler` function.
+	// Note that this method can override a key stored by a handler's fields.
+	ac.AddFields(func(ctx iris.Context, fields *accesslog.Fields) {
+		if sess := sessions.Get(ctx); sess != nil {
+			fields.Set("session_id", sess.ID())
+
+			sess.Visit(func(k string, v interface{}) {
+				fields.Set(k, v)
+			})
+		}
+	})
+	// Add a custom field of "auth" when basic auth is available.
+	ac.AddFields(func(ctx iris.Context, fields *accesslog.Fields) {
+		if username, password, ok := ctx.Request().BasicAuth(); ok {
+			fields.Set("auth", username+":"+password)
+		}
+	})
+
+	return ac
+
 	/*
 		Use a file directly:
 		ac := accesslog.File("./access.log")
@@ -41,6 +72,8 @@ func main() {
 
 		Add second output:
 		ac.AddOutput(app.Logger().Printer)
+		OR:
+		accesslog.New(io.MultiWriter(w, os.Stdout))
 
 		Change format (after output was set):
 		ac.SetFormatter(&accesslog.JSON{Indent: "  "})
@@ -51,17 +84,11 @@ func main() {
 		    Text: "{{.Now.Format .TimeFormat}}|{{.Latency}}|{{.Method}}|{{.Path}}|{{.RequestValuesLine}}|{{.Code}}|{{.BytesReceivedLine}}|{{.BytesSentLine}}|{{.Request}}|{{.Response}}|\n",
 		    // Default ^
 		})
-
-		Set custom request fields:
-		ac.AddField(func(ctx iris.Context) (string, interface{}) {
-		    v := ctx.RemoteAddr()
-		    if v == "" {
-		        return "", nil
-		    }
-		    // the log entry name and its value.
-		    return "IP", v
-		})
 	*/
+}
+
+func main() {
+	ac := makeAccessLog()
 
 	defer ac.Close()
 	iris.RegisterOnInterrupt(func() {
@@ -73,12 +100,25 @@ func main() {
 	app.UseRouter(ac.Handler)
 	//
 
+	// Register other middlewares...
+	app.UseRouter(requestid.New())
+
 	// Register some routes...
 	app.HandleDir("/", iris.Dir("./public"))
 
 	app.Get("/user/{username}", userHandler)
 	app.Post("/read_body", readBodyHandler)
 	app.Get("/html_response", htmlResponse)
+
+	basicAuth := basicauth.Default(map[string]string{
+		"admin": "admin",
+	})
+	app.Get("/admin", basicAuth, adminHandler)
+
+	sess := sessions.New(sessions.Config{Cookie: "my_session_id", AllowReclaim: true})
+	app.Get("/session", sess.Handler(), sessionHandler)
+
+	app.Get("/fields", fieldsHandler)
 	//
 
 	app.Listen(":8080")
@@ -101,3 +141,28 @@ func userHandler(ctx iris.Context) {
 func htmlResponse(ctx iris.Context) {
 	ctx.HTML("<h1>HTML Response</h1>")
 }
+
+func adminHandler(ctx iris.Context) {
+	username, password, _ := ctx.Request().BasicAuth()
+	// of course you don't want that in production:
+	ctx.HTML("<h2>Username: %s</h2><h3>Password: %s</h3>", username, password)
+}
+
+func sessionHandler(ctx iris.Context) {
+	sess := sessions.Get(ctx)
+	sess.Set("session_test_key", "session_test_value")
+
+	ctx.WriteString("OK")
+}
+
+func fieldsHandler(ctx iris.Context) {
+	now := time.Now()
+	logFields := accesslog.GetFields(ctx)
+	defer func() {
+		logFields.Set("fieldsHandler_latency", time.Since(now).Round(time.Second))
+	}()
+
+	// simulate a heavy job...
+	time.Sleep(2 * time.Second)
+	ctx.WriteString("OK")
+}