121 lines
4 KiB
Go
121 lines
4 KiB
Go
package postgres
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import (
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"context"
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"telesrv/internal/domain"
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"telesrv/internal/readmodelcache"
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)
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// ChannelRowCache 是「共享频道行」(channels 表一行 → domain.Channel) 的进程内强一致缓存,
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// 由统一缓存原语 readmodelcache.Cache 承载(LRU 单条驱逐 / epoch 守卫 / singleflight 内建)。
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//
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// 只缓存全 viewer 通用、变更不频繁的频道行；per-viewer 的 member(权限/读态) 由
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// ChannelMemberCache 以 (channel_id,user_id) 单独隔离,dialog(top/未读)、boost 仍实时查 PG。
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//
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// 一致性靠统一 read-model PG LISTEN/NOTIFY 实时失效(见 ReadModelChangeListener)而非 TTL：
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// channels 表上的 read-model 触发器在提交时发布 channel_base 事件,listener 收到即 delete
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// 对应条目；listener (重)连接时整表 flush,兜住断连窗口内丢失的通知。无 TTL,故 epoch 守卫
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// 是防永久 stale 的唯一保障(已内建于原语)。
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//
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// 仅在连接池句柄(非事务)上消费(见 ChannelStore.cacheActive)：事务内一律实时读,保证读己写。
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type ChannelRowCache struct {
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cache *readmodelcache.Cache[int64, domain.Channel]
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}
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// NewChannelRowCache 创建容量为 max 的频道行缓存；max<=0 返回 nil(表示禁用,调用方按 nil 跳过)。
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func NewChannelRowCache(max int) *ChannelRowCache {
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cache := readmodelcache.New[int64, domain.Channel](readmodelcache.Config[int64, domain.Channel]{
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MaxEntries: max,
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Clone: cloneChannelRow,
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})
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if cache == nil {
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return nil
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}
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return &ChannelRowCache{cache: cache}
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}
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func (c *ChannelRowCache) get(id int64) (domain.Channel, bool) {
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if c == nil || id == 0 {
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return domain.Channel{}, false
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}
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return c.cache.Peek(id)
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}
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func (c *ChannelRowCache) getOrLoad(ctx context.Context, id int64, load func() (domain.Channel, error)) (domain.Channel, error) {
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if c == nil {
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return load()
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}
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return c.cache.GetOrLoad(ctx, id, load)
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}
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// getOrLoadBatch resolves a page of shared channel rows with one database read
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// for all misses. A zero-ID Channel is the negative-cache sentinel for an ID
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// that disappeared between the owner-state query and shared-row hydration;
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// channel_base invalidation removes both positive and negative entries.
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func (c *ChannelRowCache) getOrLoadBatch(
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ctx context.Context,
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ids []int64,
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load func(context.Context, []int64) (map[int64]domain.Channel, error),
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) (map[int64]domain.Channel, error) {
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if c == nil {
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return load(ctx, ids)
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}
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return c.cache.GetOrLoadBatch(
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ctx,
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ids,
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func(int64) (int64, bool) { return 0, true },
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func(ctx context.Context, missing []int64) (map[int64]domain.Channel, error) {
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loaded, err := load(ctx, missing)
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if err != nil {
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return nil, err
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}
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// GetOrLoadBatch requires an explicit value for every key so absent
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// rows do not immediately stampede the database again.
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for _, id := range missing {
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if _, ok := loaded[id]; !ok {
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loaded[id] = domain.Channel{}
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}
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}
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return loaded, nil
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},
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)
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}
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func (c *ChannelRowCache) put(ch domain.Channel) {
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if c == nil || ch.ID == 0 {
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return
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}
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c.cache.Store(ch.ID, ch)
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}
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// delete 失效单个频道(listener 收到该 id 的变更通知时调用)。
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func (c *ChannelRowCache) delete(id int64) {
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if c == nil || id == 0 {
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return
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}
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c.cache.Invalidate(id)
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}
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// flush 清空整表(listener 每次 (重)连接、建立 LISTEN 后调用,兜住断连窗口内丢失的通知)。
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func (c *ChannelRowCache) flush() {
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if c == nil {
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return
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}
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c.cache.Flush()
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}
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// cloneChannelRow 深拷频道行的可变字段(切片),使缓存与调用方互不别名污染。
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func cloneChannelRow(ch domain.Channel) domain.Channel {
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if ch.PhotoStripped != nil {
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ch.PhotoStripped = append([]byte(nil), ch.PhotoStripped...)
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}
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if ch.ReactionPolicy.Emoticons != nil {
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ch.ReactionPolicy.Emoticons = append([]string(nil), ch.ReactionPolicy.Emoticons...)
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}
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if ch.ReactionPolicy.CustomEmojiIDs != nil {
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ch.ReactionPolicy.CustomEmojiIDs = append([]int64(nil), ch.ReactionPolicy.CustomEmojiIDs...)
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}
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ch.Wallpaper = domain.CloneWallpaperPtr(ch.Wallpaper)
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return ch
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}
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