生成临时头像ID链接

解决的问题：之前是根据评论ID生成对应的链接，问题是，不同的评论可能是
同一个人，所以导致同一个人也有不同的头像链接。会导致网络请求与流量的增加。

方案：后台根据相同的邮箱生成相同的ID。前端通过此ID来获取头像。

实现：能简单的哈希生成算法，对相同的邮箱在服务重启后生成相同的ID。

gateway/main.go

@@ -82,7 +82,7 @@ func (g *Gateway) runHTTPService(ctx context.Context, mux *http.ServeMux, mux2 *
 	handle("GET", `/v3/api`, serveProtoDocsFile(`index.html`))
 	handle("GET", `/v3/api/swagger`, serveProtoDocsFile(`taoblog.swagger.json`))
 
-	handle(`GET`, `/v3/comments/{id}/avatar`, g.GetAvatar)
+	handle(`GET`, `/v3/avatar/{id}`, g.GetAvatar)
 
 	handle(`GET`, `/v3/posts/{post_id}/files`, g.ListFiles)
 	handle(`GET`, `/v3/posts/{post_id}/files/{file=**}`, g.GetFile)
@@ -103,13 +103,12 @@ func redirectToGrafana(w http.ResponseWriter, req *http.Request, params map[stri
 }
 
 func (g *Gateway) GetAvatar(w http.ResponseWriter, req *http.Request, params map[string]string) {
-	commentID, err := strconv.Atoi(params[`id`])
+	ephemeral, err := strconv.Atoi(params[`id`])
 	if err != nil {
 		panic(err)
 	}
-
 	in := &protocols.GetAvatarRequest{
-		CommentID:       int64(commentID),
+		Ephemeral:       ephemeral,
 		IfModifiedSince: req.Header.Get("If-Modified-Since"),
 		IfNoneMatch:     req.Header.Get("If-None-Match"),
 		SetStatus: func(statusCode int) {

protocols/comment.proto

@@ -24,6 +24,8 @@ message Comment {
 	// 前端用户是否可以编辑此评论？
 	// 仅在 list/create 接口中返回。
 	bool can_edit = 17;
+	// 头像内部临时ID
+	int32 avatar = 18;
 }
 
 message GetCommentRequest {

protocols/message.go

@@ -3,7 +3,7 @@ package protocols
 import "io"
 
 type GetAvatarRequest struct {
-	CommentID       int64
+	Ephemeral       int
 	IfModifiedSince string
 	IfNoneMatch     string
 	SetStatus       func(statusCode int)

service/avatar.go

@@ -2,16 +2,78 @@ package service
 
 import (
 	"fmt"
+	"hash/fnv"
 	"io"
 	"net/http"
+	"strings"
+	"sync"
 
 	"github.com/movsb/taoblog/protocols"
-	"github.com/movsb/taoblog/service/models"
 	"github.com/movsb/taoblog/service/modules/avatar"
 )
 
+type AvatarCache struct {
+	id2email map[int]string
+	email2id map[string]int
+	lock     sync.RWMutex
+}
+
+func NewAvatarCache() *AvatarCache {
+	return &AvatarCache{
+		id2email: make(map[int]string),
+		email2id: make(map[string]int),
+	}
+}
+
+// 简单的“一致性”哈希生成算法。
+func (c *AvatarCache) id(email string) int {
+	hash := fnv.New32()
+	hash.Write([]byte(email))
+	sum := hash.Sum32() & 0x7fffffff
+	for {
+		e, ok := c.id2email[int(sum)]
+		if ok && e != email {
+			sum++
+			continue
+		}
+		break
+	}
+	return int(sum)
+}
+
+func (c *AvatarCache) ID(email string) int {
+	c.lock.Lock()
+	defer c.lock.Unlock()
+
+	email = strings.ToLower(email)
+
+	if id, ok := c.email2id[email]; ok {
+		return id
+	}
+
+	next := c.id(email)
+
+	c.email2id[email] = int(next)
+	c.id2email[next] = email
+
+	return next
+}
+
+func (c *AvatarCache) Email(id int) string {
+	c.lock.RLock()
+	defer c.lock.RUnlock()
+
+	return c.id2email[id]
+}
+
 // GetAvatar ...
 func (s *Service) GetAvatar(in *protocols.GetAvatarRequest) {
+	email := s.avatarCache.Email(in.Ephemeral)
+	if email == "" {
+		in.SetStatus(http.StatusNotFound)
+		return
+	}
+
 	p := avatar.Params{
 		Headers: make(http.Header),
 	}
@@ -23,10 +85,8 @@ func (s *Service) GetAvatar(in *protocols.GetAvatarRequest) {
 		p.Headers.Add("If-None-Match", in.IfNoneMatch)
 	}
 
-	var comment models.Comment
-	s.tdb.Select(`email`).Where(`id = ?`, in.CommentID).MustFind(&comment)
-
-	resp, err := avatar.Get(comment.Email, &p)
+	// TODO 并没有限制获取未公开发表文章的评论。
+	resp, err := avatar.Get(email, &p)
 	if err != nil {
 		in.SetStatus(500)
 		fmt.Fprint(in.W, err)

service/comment.go

@@ -35,12 +35,16 @@ func (s *Service) GetComment2(name int64) *models.Comment {
 	return &comment
 }
 
+func (s *Service) avatar(email string) int {
+	return s.avatarCache.ID(email)
+}
+
 // GetComment ...
 // TODO perm check
 // TODO remove email & user
 func (s *Service) GetComment(ctx context.Context, req *protocols.GetCommentRequest) (*protocols.Comment, error) {
 	user := s.auth.AuthGRPC(ctx)
-	return s.GetComment2(req.Id).ToProtocols(s.isAdminEmail, user, s.geoLocation, ""), nil
+	return s.GetComment2(req.Id).ToProtocols(s.isAdminEmail, user, s.geoLocation, "", s.avatar), nil
 }
 
 // UpdateComment ...
@@ -91,7 +95,7 @@ func (s *Service) UpdateComment(ctx context.Context, req *protocols.UpdateCommen
 		s.tdb.Where(`id=?`, req.Comment.Id).MustFind(&comment)
 	}
 
-	return comment.ToProtocols(s.isAdminEmail, user, s.geoLocation, ""), nil
+	return comment.ToProtocols(s.isAdminEmail, user, s.geoLocation, "", s.avatar), nil
 }
 
 // DeleteComment ...
@@ -131,7 +135,7 @@ func (s *Service) ListComments(ctx context.Context, in *protocols.ListCommentsRe
 			stmt.InnerJoin("posts", "comments.post_id = posts.id AND posts.status = 'public'")
 		}
 		stmt.MustFind(&parents)
-		parentProtocolComments = parents.ToProtocols(s.isAdminEmail, user, s.geoLocation, userIP)
+		parentProtocolComments = parents.ToProtocols(s.isAdminEmail, user, s.geoLocation, userIP, s.avatar)
 	}
 
 	needChildren := in.Mode == protocols.ListCommentsMode_ListCommentsModeTree && len(parentProtocolComments) > 0
@@ -150,7 +154,7 @@ func (s *Service) ListComments(ctx context.Context, in *protocols.ListCommentsRe
 				stmt.InnerJoin("posts", "comments.post_id = posts.id AND posts.status = 'public'")
 			}
 			stmt.MustFind(&children)
-			childrenProtocolComments = children.ToProtocols(s.isAdminEmail, user, s.geoLocation, userIP)
+			childrenProtocolComments = children.ToProtocols(s.isAdminEmail, user, s.geoLocation, userIP, s.avatar)
 		}
 		{
 			childrenMap := make(map[int64][]*protocols.Comment, len(parentProtocolComments))
@@ -327,7 +331,7 @@ func (s *Service) CreateComment(ctx context.Context, in *protocols.Comment) (*pr
 
 	s.doCommentNotification(&comment)
 
-	return comment.ToProtocols(s.isAdminEmail, user, s.geoLocation, ip), nil
+	return comment.ToProtocols(s.isAdminEmail, user, s.geoLocation, ip, s.avatar), nil
 }
 
 func (s *Service) updateCommentsCount() {

service/main.go

@@ -36,6 +36,8 @@ type Service struct {
 	store  storage.Store
 	cache  *memory_cache.MemoryCache
 
+	avatarCache *AvatarCache
+
 	// 搜索引擎启动需要时间，所以如果网站一运行即搜索，则可能出现引擎不可用
 	// 的情况，此时此值为空。
 	searcher atomic.Pointer[search.Engine]
@@ -60,6 +62,8 @@ func NewService(cfg *config.Config, db *sql.DB, auther *auth.Auth) *Service {
 		store:  localStorage,
 		cache:  memory_cache.NewMemoryCache(time.Minute * 10),
 		cmtgeo: commentgeo.NewCommentGeo(context.TODO()),
+
+		avatarCache: NewAvatarCache(),
 	}
 
 	s.cmtntf = &comment_notify.CommentNotifier{