xfy
5f470993ff
- Change FileInfoCache.mu from sync.Mutex to sync.RWMutex - Get method uses RLock for concurrent read access - Stats method uses RLock for read-only operation - Double-check pattern for lock upgrades (TTL expiry, LRU move) This improves concurrent read performance for the FileInfo cache, which is read-heavy in static file serving scenarios. Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
153 lines
3.4 KiB
Go
153 lines
3.4 KiB
Go
// Package handler 提供 HTTP 请求处理器，包括路由、静态文件服务和零拷贝传输。
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//
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// 该文件实现 FileInfo 缓存，用于减少 os.Stat 调用。
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// 替代原 fd 池设计，避免 fd 所有权问题。
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//
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// 设计说明：
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// - 使用 TTL-only 新鲜度策略：缓存命中时不验证 ModTime
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// - 理由：每次验证 ModTime 仍需 os.Stat 调用，违背缓存目的
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// - 风险：TTL 内文件修改可能返回旧 FileInfo，但静态文件通常不频繁修改
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//
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// 作者：xfy
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package handler
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import (
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"container/list"
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"os"
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"sync"
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"time"
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)
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const (
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fileInfoCacheMaxEntries = 2000
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fileInfoCacheTTL = 10 * time.Second
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)
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// fileInfoEntry FileInfo 缓存条目
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type fileInfoEntry struct {
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path string
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info os.FileInfo
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cachedAt time.Time
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element *list.Element
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}
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// FileInfoCache FileInfo 缓存（O(1) LRU）
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type FileInfoCache struct {
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entries map[string]*fileInfoEntry
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lruList *list.List
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mu sync.RWMutex
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}
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// NewFileInfoCache 创建 FileInfo 缓存
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func NewFileInfoCache() *FileInfoCache {
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return &FileInfoCache{
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entries: make(map[string]*fileInfoEntry, fileInfoCacheMaxEntries),
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lruList: list.New(),
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}
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}
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// Get 获取缓存的 FileInfo
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func (c *FileInfoCache) Get(filePath string) (os.FileInfo, bool) {
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c.mu.RLock()
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entry, ok := c.entries[filePath]
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if !ok {
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c.mu.RUnlock()
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return nil, false
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}
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// 检查 TTL（只读检查）
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if time.Since(entry.cachedAt) > fileInfoCacheTTL {
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c.mu.RUnlock()
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// 升级为写锁删除过期条目
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c.mu.Lock()
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// double-check：可能已被其他请求删除或更新
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if entry, ok := c.entries[filePath]; ok && time.Since(entry.cachedAt) > fileInfoCacheTTL {
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c.lruList.Remove(entry.element)
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delete(c.entries, filePath)
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}
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c.mu.Unlock()
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return nil, false
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}
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c.mu.RUnlock()
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// LRU 移动需要写锁
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c.mu.Lock()
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// double-check：条目可能已被删除
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if entry, ok := c.entries[filePath]; ok {
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c.lruList.MoveToFront(entry.element)
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c.mu.Unlock()
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return entry.info, true
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}
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c.mu.Unlock()
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return nil, false
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}
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// Set 缓存 FileInfo
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func (c *FileInfoCache) Set(filePath string, info os.FileInfo) {
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c.mu.Lock()
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defer c.mu.Unlock()
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// 已存在，更新
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if entry, ok := c.entries[filePath]; ok {
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entry.info = info
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entry.cachedAt = time.Now()
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c.lruList.MoveToFront(entry.element)
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return
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}
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// 淘汰最久未用的
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if c.lruList.Len() >= fileInfoCacheMaxEntries {
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if oldest := c.lruList.Back(); oldest != nil {
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if entry, ok := oldest.Value.(*fileInfoEntry); ok {
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delete(c.entries, entry.path)
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}
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c.lruList.Remove(oldest)
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}
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}
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// 插入新条目
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entry := &fileInfoEntry{
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path: filePath,
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info: info,
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cachedAt: time.Now(),
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}
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entry.element = c.lruList.PushFront(entry)
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c.entries[filePath] = entry
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}
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// Delete 删除缓存条目
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func (c *FileInfoCache) Delete(filePath string) {
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c.mu.Lock()
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defer c.mu.Unlock()
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if entry, ok := c.entries[filePath]; ok {
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c.lruList.Remove(entry.element)
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delete(c.entries, filePath)
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}
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}
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// Clear 清空缓存
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func (c *FileInfoCache) Clear() {
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c.mu.Lock()
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defer c.mu.Unlock()
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c.entries = make(map[string]*fileInfoEntry, fileInfoCacheMaxEntries)
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c.lruList = list.New()
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}
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// Stats 返回缓存统计
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func (c *FileInfoCache) Stats() FileInfoCacheStats {
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c.mu.RLock()
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defer c.mu.RUnlock()
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return FileInfoCacheStats{
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Entries: len(c.entries),
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}
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}
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// FileInfoCacheStats FileInfo 缓存统计
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type FileInfoCacheStats struct {
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Entries int
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}
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