370 lines
9.5 KiB
Go
370 lines
9.5 KiB
Go
package sse
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import (
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"encoding/json"
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"fmt"
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"net/http"
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"sync"
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"time"
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"github.com/google/uuid"
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)
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// eventRing 是单用户事件的有界环形缓冲区。
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//
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// EventSource 断线重连时自带 Last-Event-ID 头：服务端据此回放断线期间的事件。
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// 没有它，重连后永远看不到断线期间收到的邮件 —— 而这正是实时协作的体验核心。
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//
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// 缓冲区大小 500 条：一条事件约 200B（typical），500 条 ≈ 100KB/用户。
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// 20 个在线用户 ≈ 2MB，远低于 OOM 风险。
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type eventRing struct {
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mu sync.Mutex
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events []StoredEvent
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cap int
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head int // 下一次写入的位置
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full bool
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}
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// StoredEvent 是缓冲区中的单条事件。
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type StoredEvent struct {
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ID string // 自增序列号，EventSource 的 Last-Event-ID 值
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EventType string
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Data []byte
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Timestamp time.Time
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}
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func newEventRing(cap int) *eventRing {
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return &eventRing{events: make([]StoredEvent, cap), cap: cap}
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}
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// push 追加一条事件到缓冲区。满了就覆盖最旧的。
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func (r *eventRing) push(evt StoredEvent) {
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r.mu.Lock()
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defer r.mu.Unlock()
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r.events[r.head] = evt
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r.head = (r.head + 1) % r.cap
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if r.head == 0 && !r.full {
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r.full = true
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}
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}
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// replay 从 afterID 之后的所有事件回放给 ResponseWriter。
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// afterID 为空时：缓冲区未满不回放（首次连接无历史）；满了也不回放
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// （首次连接的 EventSource 不传 Last-Event-ID）。
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// afterID 非空时：找到该 ID 的位置，从下一条开始回放。
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func (r *eventRing) replay(afterID string, flush http.Flusher, res http.ResponseWriter) {
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r.mu.Lock()
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defer r.mu.Unlock()
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if afterID == "" {
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return // 首次连接，不回放
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}
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start := -1
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total := r.cap
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for i := 0; i < r.cap; i++ {
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idx := (r.head + i) % r.cap
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if r.events[idx].ID == afterID {
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start = (idx + 1) % r.cap
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break
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}
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}
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if start == -1 {
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// afterID 不在缓冲区里（已被覆盖或从未存在），
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// 回放缓冲区里所有事件 —— 宁可重复也不丢失
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start = 0
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if !r.full {
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total = r.head
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}
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} else {
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// 从 start 开始到 head 结束
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total = r.head - start
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if total < 0 {
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total += r.cap
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}
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}
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for i := 0; i < total; i++ {
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idx := (start + i) % r.cap
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evt := &r.events[idx]
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if evt.ID == "" {
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continue
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}
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fmt.Fprintf(res, "id: %s\nevent: %s\ndata: %s\n\n", evt.ID, evt.EventType, evt.Data)
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}
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flush.Flush()
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}
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// Client 是一个 SSE 连接客户端
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type Client struct {
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ID string
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AgentName string // 非空 = Agent 侧连接
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UserName string // 非空 = 已登录人类用户的前端连接
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Res http.ResponseWriter
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Flusher http.Flusher
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done chan struct{}
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}
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// Manager 管理所有 SSE 客户端连接
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type Manager struct {
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mu sync.RWMutex
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clients map[string]*Client
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// eventBuffer：per-user/agent 的事件环形缓冲区，供 Last-Event-ID 回放。
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// Key 是 userName（人类）或 agentName（Agent），二者共享一个 map。
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// 不是连接级别的 —— 同一用户断线重连后仍能从同一个缓冲区拿到断线期间的事件。
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eventBuffer map[string]*eventRing
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bufMu sync.RWMutex
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seqCounter uint64 // 全局递增序列号，用作事件 ID
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seqMu sync.Mutex
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}
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// Default 是全局 SSE 管理器
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var Default = &Manager{
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clients: make(map[string]*Client),
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eventBuffer: make(map[string]*eventRing),
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}
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const eventBufferCap = 500 // 每用户最多保留 500 条事件
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// nextEventID 生成下一个全局递增的事件 ID
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func (m *Manager) nextEventID() string {
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m.seqMu.Lock()
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defer m.seqMu.Unlock()
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m.seqCounter++
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return fmt.Sprintf("%d", m.seqCounter)
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}
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// getOrCreateRing 获取或创建用户的环形缓冲区
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func (m *Manager) getOrCreateRing(key string) *eventRing {
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if key == "" {
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return nil
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}
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m.bufMu.RLock()
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ring, ok := m.eventBuffer[key]
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m.bufMu.RUnlock()
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if ok {
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return ring
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}
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m.bufMu.Lock()
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defer m.bufMu.Unlock()
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// double-check
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if ring, ok = m.eventBuffer[key]; ok {
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return ring
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}
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ring = newEventRing(eventBufferCap)
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m.eventBuffer[key] = ring
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return ring
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}
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// AddClient 注册一个新 SSE 客户端（agentName 与 userName 二者恰其一）
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func (m *Manager) AddClient(res http.ResponseWriter, r *http.Request, agentName, userName string) *Client {
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flusher, ok := res.(http.Flusher)
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if !ok {
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return nil
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}
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id := uuid.New().String()[:8]
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client := &Client{
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ID: id,
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AgentName: agentName,
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UserName: userName,
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Res: res,
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Flusher: flusher,
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done: make(chan struct{}),
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}
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// 设置 SSE 响应头
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res.Header().Set("Content-Type", "text/event-stream")
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res.Header().Set("Cache-Control", "no-cache")
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res.Header().Set("Connection", "keep-alive")
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res.Header().Set("X-Accel-Buffering", "no")
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// Last-Event-ID 回放：EventSource 断线重连时自带这个头，
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// 服务端据此把断线期间的事件补上 —— 否则重连后永远看不到那段时间的邮件。
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lastID := r.Header.Get("Last-Event-ID")
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key := m.bufferKey(userName, agentName)
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if ring := m.getOrCreateRing(key); ring != nil && lastID != "" {
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ring.replay(lastID, flusher, res)
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}
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m.mu.Lock()
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m.clients[id] = client
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m.mu.Unlock()
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// 发送连接确认（带 id 让客户端知道自己的 ID）
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evtID := m.nextEventID()
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client.SendWithID(evtID, "connected", map[string]string{"id": id})
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// 启动心跳
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go m.heartbeat(client)
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fmt.Printf("[SSE] Client connected: %s (agent=%q user=%q) lastID=%q\n", id, agentName, userName, lastID)
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return client
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}
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// bufferKey 返回缓冲区 key：优先 userName（人类），其次 agentName（Agent）
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func (m *Manager) bufferKey(userName, agentName string) string {
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if userName != "" {
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return "u:" + userName
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}
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if agentName != "" {
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return "a:" + agentName
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}
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return ""
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}
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// RemoveClient 移除一个客户端
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func (m *Manager) RemoveClient(id string) {
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m.mu.Lock()
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if c, ok := m.clients[id]; ok {
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close(c.done)
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delete(m.clients, id)
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fmt.Printf("[SSE] Client disconnected: %s\n", id)
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}
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m.mu.Unlock()
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}
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// SendToAgent 向指定 Agent 名的所有客户端推送事件
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func (m *Manager) SendToAgent(agentName, eventType string, data interface{}) {
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if agentName == "" {
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return
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}
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// 写入缓冲区
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evtID := m.nextEventID()
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raw, _ := json.Marshal(data)
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if ring := m.getOrCreateRing(m.bufferKey("", agentName)); ring != nil {
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ring.push(StoredEvent{ID: evtID, EventType: eventType, Data: raw, Timestamp: time.Now()})
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}
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m.mu.RLock()
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defer m.mu.RUnlock()
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for _, c := range m.clients {
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if c.AgentName == agentName {
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c.SendWithID(evtID, eventType, data)
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}
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}
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}
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// SendToUser 向指定人类用户的所有前端连接推送事件
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func (m *Manager) SendToUser(userName, eventType string, data interface{}) {
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if userName == "" {
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return
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}
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evtID := m.nextEventID()
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raw, _ := json.Marshal(data)
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if ring := m.getOrCreateRing(m.bufferKey(userName, "")); ring != nil {
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ring.push(StoredEvent{ID: evtID, EventType: eventType, Data: raw, Timestamp: time.Now()})
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}
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m.mu.RLock()
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defer m.mu.RUnlock()
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for _, c := range m.clients {
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if c.UserName == userName {
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c.SendWithID(evtID, eventType, data)
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}
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}
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}
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// SendToRecipient 根据收件人名同时尝试 Agent 通道与人类用户通道
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func (m *Manager) SendToRecipient(name, eventType string, data interface{}) {
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if name == "" {
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return
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}
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evtID := m.nextEventID()
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raw, _ := json.Marshal(data)
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// 同时写两个缓冲区（人类或 Agent，或两者都有）
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if ring := m.getOrCreateRing(m.bufferKey(name, "")); ring != nil {
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ring.push(StoredEvent{ID: evtID, EventType: eventType, Data: raw, Timestamp: time.Now()})
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}
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if ring := m.getOrCreateRing(m.bufferKey("", name)); ring != nil {
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ring.push(StoredEvent{ID: evtID, EventType: eventType, Data: raw, Timestamp: time.Now()})
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}
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m.mu.RLock()
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defer m.mu.RUnlock()
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for _, c := range m.clients {
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if c.AgentName == name || c.UserName == name {
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c.SendWithID(evtID, eventType, data)
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}
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}
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}
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// Broadcast 向所有客户端广播事件（心跳、系统通知等）
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func (m *Manager) Broadcast(eventType string, data interface{}) {
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evtID := m.nextEventID()
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raw, _ := json.Marshal(data)
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// 广播写入所有用户的缓冲区（确保任何用户重连都能回放）
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m.bufMu.RLock()
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for key, ring := range m.eventBuffer {
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ring.push(StoredEvent{ID: evtID, EventType: eventType, Data: raw, Timestamp: time.Now()})
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_ = key // key 仅用于日志，此处不需
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}
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m.bufMu.RUnlock()
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m.mu.RLock()
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defer m.mu.RUnlock()
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for _, c := range m.clients {
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c.SendWithID(evtID, eventType, data)
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}
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}
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// ClientCount 返回当前连接数
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func (m *Manager) ClientCount() int {
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m.mu.RLock()
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defer m.mu.RUnlock()
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return len(m.clients)
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}
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// Send 向单个客户端发送事件（无 ID）
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func (c *Client) Send(eventType string, data interface{}) {
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defer func() { recover() }()
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jsonData, err := json.Marshal(data)
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if err != nil {
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return
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}
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fmt.Fprintf(c.Res, "event: %s\ndata: %s\n\n", eventType, jsonData)
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c.Flusher.Flush()
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}
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// SendWithID 向单个客户端发送带 ID 的事件
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func (c *Client) SendWithID(id, eventType string, data interface{}) {
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defer func() { recover() }()
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jsonData, err := json.Marshal(data)
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if err != nil {
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return
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}
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fmt.Fprintf(c.Res, "id: %s\nevent: %s\ndata: %s\n\n", id, eventType, jsonData)
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c.Flusher.Flush()
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}
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// heartbeat 定期发送心跳保活
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func (m *Manager) heartbeat(client *Client) {
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ticker := time.NewTicker(30 * time.Second)
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defer ticker.Stop()
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for {
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select {
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case <-client.done:
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return
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case <-ticker.C:
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defer func() { recover() }()
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fmt.Fprintf(client.Res, ": heartbeat\n\n")
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client.Flusher.Flush()
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}
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}
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}
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