xfy
e44cfc7128
FileInfoCache.Get previously acquired TWO locks on every cache hit: 1. RLock → check existence + TTL 2. Release RLock → Lock → MoveToFront (LRU update) → Unlock The MoveToFront on every hit forced a read-to-write lock upgrade, creating contention under concurrent reads. Apply approximate LRU: skip MoveToFront on Get (read) path entirely. LRU position is only updated in Set (write) path. This is the same pattern already used by internal/cache/file_cache.go. Result: Get fast path reduced from 2 lock acquisitions to 1 RLock. TTL-expired entries still use double-check locking for safe removal.
103 lines
2.3 KiB
Go
103 lines
2.3 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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// 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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if time.Since(entry.cachedAt) > fileInfoCacheTTL {
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c.mu.RUnlock()
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c.mu.Lock()
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if e, ok := c.entries[filePath]; ok && time.Since(e.cachedAt) > fileInfoCacheTTL {
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c.lruList.Remove(e.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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info := entry.info
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c.mu.RUnlock()
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return info, true
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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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// 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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