Update

Author: devlights

examples/slog/15.custom-handler1/Taskfile.yml

@@ -0,0 +1,11 @@
+# https://taskfile.dev
+
+version: '3'
+
+tasks:
+  default:
+    cmds:
+      - task: run
+  run:
+    cmds:
+      - go run main.go

examples/slog/15.custom-handler1/main.go

@@ -0,0 +1,85 @@
+package main
+
+import (
+	"context"
+	"log/slog"
+	"os"
+	"runtime"
+	"strconv"
+	"sync"
+	"time"
+)
+
+type (
+	counterHandler struct {
+		slog.Handler
+		count *int
+		mu    *sync.Mutex
+	}
+)
+
+func newHandler(handler slog.Handler) *counterHandler {
+	var (
+		count = 0
+		mu    sync.Mutex
+	)
+	return &counterHandler{Handler: handler, count: &count, mu: &mu}
+}
+
+func (me *counterHandler) Handle(ctx context.Context, r slog.Record) error {
+	me.mu.Lock()
+	defer me.mu.Unlock()
+
+	r.AddAttrs(slog.String("millis", time.Now().Format(".000")))
+	r.AddAttrs(slog.Int("count", *me.count))
+	*me.count++
+
+	return me.Handler.Handle(ctx, r)
+}
+
+func (me *counterHandler) WithAttrs(attrs []slog.Attr) slog.Handler {
+	return &counterHandler{Handler: me.Handler.WithAttrs(attrs), count: me.count, mu: me.mu}
+}
+
+func (me *counterHandler) WithGroup(name string) slog.Handler {
+	return &counterHandler{Handler: me.Handler.WithGroup(name), count: me.count, mu: me.mu}
+}
+
+func main() {
+	var (
+		level = &slog.LevelVar{}
+		opt   = &slog.HandlerOptions{
+			Level:       level,
+			ReplaceAttr: replaceAttr,
+		}
+		writer  = os.Stdout
+		handler = newHandler(slog.NewTextHandler(writer, opt))
+		logger  = slog.New(handler)
+
+		wg             sync.WaitGroup
+		goroutineCount = runtime.NumCPU() * 2
+		loopCount      = 2
+	)
+
+	logger.Info("Start", "NumCPU", runtime.NumCPU(), "goroutineCount", goroutineCount)
+
+	wg.Add(goroutineCount)
+	for i := range goroutineCount {
+		go func(logger *slog.Logger) {
+			defer wg.Done()
+			for i := range loopCount {
+				logger.Info(strconv.Itoa(i))
+			}
+		}(logger.With("goroutine", i))
+	}
+
+	wg.Wait()
+}
+
+func replaceAttr(g []string, a slog.Attr) slog.Attr {
+	if a.Key == slog.TimeKey {
+		return slog.Attr{}
+	}
+
+	return a
+}