Use LRU cache for runners in HTTP API

Author: pan93412

main.go

@@ -8,10 +8,10 @@ import (
 	"log/slog"
 	"net/http"
 	"os"
-	"sync"
 	"time"
 
 	sqlrunner "github.com/database-playground/sqlrunner/lib"
+	lru "github.com/hashicorp/golang-lru/v2"
 	"golang.org/x/sync/singleflight"
 )
 
@@ -21,7 +21,15 @@ func main() {
 		addr = ":" + os.Getenv("PORT")
 	}
 
-	service := &SqlQueryService{}
+	runnersCache, err := lru.New[string, *sqlrunner.SQLRunner](20)
+	if err != nil {
+		slog.Error("failed to create LRU cache for runners", slog.Any("error", err))
+		os.Exit(1)
+	}
+
+	service := &SqlQueryService{
+		runnersCache: runnersCache,
+	}
 	http.Handle("POST /query", service)
 
 	slog.Info("Listening", slog.String("addr", addr))
@@ -32,9 +40,8 @@ func main() {
 }
 
 type SqlQueryService struct {
-	// fixme: lru
-	runners sync.Map
-	sfgroup singleflight.Group
+	runnersCache *lru.Cache[string, *sqlrunner.SQLRunner]
+	sfgroup      singleflight.Group
 }
 
 func (s *SqlQueryService) ServeHTTP(w http.ResponseWriter, r *http.Request) {
@@ -75,9 +82,9 @@ func (s *SqlQueryService) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 
 func (s *SqlQueryService) findRunner(schema string) (*sqlrunner.SQLRunner, error) {
 	// If we have already prepared a runner for this schema, return it.
-	runner, ok := s.runners.Load(schema)
+	runner, ok := s.runnersCache.Get(schema)
 	if ok {
-		return runner.(*sqlrunner.SQLRunner), nil
+		return runner, nil
 	}
 
 	result, err, _ := s.sfgroup.Do(schema, func() (any, error) {
@@ -86,16 +93,14 @@ func (s *SqlQueryService) findRunner(schema string) (*sqlrunner.SQLRunner, error
 			return nil, fmt.Errorf("create SQLRunner: %w", err)
 		}
 
-		s.runners.Store(schema, newRunner)
+		s.runnersCache.Add(schema, newRunner)
 		return newRunner, nil
 	})
 	if err != nil {
 		return nil, err
 	}
 
 	typedResult := result.(*sqlrunner.SQLRunner)
-
-	s.runners.Store(schema, typedResult)
 	return typedResult, err
 }