优化生产日志体积：访问降噪、压缩清理与退款告警节流

跳过轮询/封面等热路径成功请求，按日 gzip 并保留可配天数，退款 max-retry 汇总告警。

backend/internal/logging/daily_writer.go

@@ -1,27 +1,35 @@
 package logging
 
 import (
+	"compress/gzip"
 	"fmt"
+	"io"
 	"os"
 	"path/filepath"
+	"strings"
 	"sync"
 	"time"
 )
 
 type dailyWriter struct {
-	mu       sync.Mutex
-	dir      string
-	prefix   string
-	location *time.Location
-	day      string
-	file     *os.File
+	mu         sync.Mutex
+	dir        string
+	prefix     string
+	location   *time.Location
+	retainDays int
+	day        string
+	file       *os.File
 }
 
-func newDailyWriter(dir string, prefix string, location *time.Location) *dailyWriter {
+func newDailyWriter(dir string, prefix string, location *time.Location, retainDays int) *dailyWriter {
+	if retainDays < 0 {
+		retainDays = 0
+	}
 	return &dailyWriter{
-		dir:      dir,
-		prefix:   prefix,
-		location: location,
+		dir:        dir,
+		prefix:     prefix,
+		location:   location,
+		retainDays: retainDays,
 	}
 }
 
@@ -55,6 +63,7 @@ func (w *dailyWriter) rotateIfNeeded(now time.Time) error {
 		return err
 	}
 
+	prevDay := w.day
 	if w.file != nil {
 		_ = w.file.Close()
 		w.file = nil
@@ -67,5 +76,94 @@ func (w *dailyWriter) rotateIfNeeded(now time.Time) error {
 	}
 	w.file = file
 	w.day = day
+
+	// 异步压缩昨日日志并清理过期文件，避免阻塞业务写路径
+	if prevDay != "" && prevDay != day {
+		go w.maintain(prevDay, now)
+	} else {
+		// 进程启动或首写：尝试压缩昨天 + 清理过期
+		yesterday := now.AddDate(0, 0, -1).Format("2006-01-02")
+		go w.maintain(yesterday, now)
+	}
+	return nil
+}
+
+func (w *dailyWriter) maintain(prevDay string, now time.Time) {
+	if prevDay != "" {
+		_ = w.compressDay(prevDay)
+	}
+	if w.retainDays > 0 {
+		_ = w.purgeOlderThan(now)
+	}
+}
+
+func (w *dailyWriter) compressDay(day string) error {
+	srcPath := filepath.Join(w.dir, fmt.Sprintf("%s-%s.log", w.prefix, day))
+	dstPath := srcPath + ".gz"
+	if _, err := os.Stat(dstPath); err == nil {
+		// 已压缩则删除明文（若仍存在）
+		_ = os.Remove(srcPath)
+		return nil
+	}
+	src, err := os.Open(srcPath)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return nil
+		}
+		return err
+	}
+	defer src.Close()
+
+	dst, err := os.OpenFile(dstPath, os.O_CREATE|os.O_WRONLY|os.O_TRUNC, 0o644)
+	if err != nil {
+		return err
+	}
+	gz := gzip.NewWriter(dst)
+	if _, err := io.Copy(gz, src); err != nil {
+		_ = gz.Close()
+		_ = dst.Close()
+		_ = os.Remove(dstPath)
+		return err
+	}
+	if err := gz.Close(); err != nil {
+		_ = dst.Close()
+		_ = os.Remove(dstPath)
+		return err
+	}
+	if err := dst.Close(); err != nil {
+		return err
+	}
+	return os.Remove(srcPath)
+}
+
+func (w *dailyWriter) purgeOlderThan(now time.Time) error {
+	// 按「日历天」比较：保留最近 retainDays 天（含当天），更早的 .log / .log.gz 删除。
+	today := time.Date(now.In(w.location).Year(), now.In(w.location).Month(), now.In(w.location).Day(), 0, 0, 0, 0, w.location)
+	cutoff := today.AddDate(0, 0, -w.retainDays) // day < cutoff 才删除；retainDays=2 且今天 12 号 → 删除 10 号之前
+	entries, err := os.ReadDir(w.dir)
+	if err != nil {
+		return err
+	}
+	prefix := w.prefix + "-"
+	for _, entry := range entries {
+		if entry.IsDir() {
+			continue
+		}
+		name := entry.Name()
+		if !strings.HasPrefix(name, prefix) {
+			continue
+		}
+		// app-2026-07-11.log 或 app-2026-07-11.log.gz
+		rest := strings.TrimPrefix(name, prefix)
+		rest = strings.TrimSuffix(rest, ".gz")
+		rest = strings.TrimSuffix(rest, ".log")
+		day, err := time.ParseInLocation("2006-01-02", rest, w.location)
+		if err != nil {
+			continue
+		}
+		if day.Before(cutoff) {
+			_ = os.Remove(filepath.Join(w.dir, name))
+		}
+	}
 	return nil
 }