feat: refactor article fetching with singleflight

- Update logging message to indicate usage of `singleflight Do` instead of `singleflight`
- Replace `GetArticleNew` function calls with `GetArticleDo` and add logging for data and request information
- Introduce a new `GetArticleDoChan` function with cache hit logging, a timeout mechanism, and simulated data retrieval delay
- Add a new loop to demonstrate the usage of `singleflight DoChan` with a wait group and a timeout for each request

Signed-off-by: Bo-Yi Wu <[email protected]>

example55-cache-hotspot-invalid/main.go

@@ -29,13 +29,26 @@ func main() {
 	}
 	wg.Wait()
 
-	slog.Info("================== using singleflight ===================")
+	slog.Info("================== using singleflight Do ===================")
 
 	wg.Add(5)
 	for i := 5; i < 10; i++ {
 		go func(req int) {
 			defer wg.Done()
-			data := db.GetArticleNew(req, 2)
+			data := db.GetArticleDo(req, 2)
+			slog.Info("data info", "data", data, "req", req)
+		}(i)
+	}
+	wg.Wait()
+
+	slog.Info("================== using singleflight DoChan ===================")
+
+	wg.Add(5)
+	for i := 10; i < 15; i++ {
+		go func(req int) {
+			defer wg.Done()
+			t := time.Duration(time.Duration(int64(req*10)) * time.Millisecond)
+			data := db.GetArticleDoChan(req, 3, t)
 			slog.Info("data info", "data", data, "req", req)
 		}(i)
 	}
@@ -64,7 +77,7 @@ func (db *DB) GetArticleOld(req int, id int) *Article {
 	return data
 }
 
-func (db *DB) GetArticleNew(req int, id int) *Article {
+func (db *DB) GetArticleDo(req int, id int) *Article {
 	data := db.cache.Get(id)
 	if data != nil {
 		slog.Info("cache hit", "id", id, "req", req)
@@ -90,3 +103,31 @@ func (db *DB) GetArticleNew(req int, id int) *Article {
 
 	return row.(*Article)
 }
+
+func (db *DB) GetArticleDoChan(req int, id int, t time.Duration) *Article {
+	data := db.cache.Get(id)
+	if data != nil {
+		slog.Info("cache hit", "id", id, "req", req)
+		return data
+	}
+
+	key := fmt.Sprintf("article:%d", id)
+	dataChan := db.engine.DoChan(key, func() (interface{}, error) {
+		slog.Info("missing cache", "id", id, "req", req)
+		data := &Article{
+			ID:      id,
+			Content: "FooBar",
+		}
+		db.cache.Set(id, data)
+		time.Sleep(115 * time.Millisecond)
+		return data, nil
+	})
+
+	select {
+	case <-time.After(t):
+		slog.Info("timeout", "id", id, "req", req)
+		return nil
+	case res := <-dataChan:
+		return res.Val.(*Article)
+	}
+}