Merge pull request #260 from okhowang/fix/loadable

fix(loadable): cache value in setChannel

Author: eko

lib/cache/loadable.go

@@ -28,6 +28,7 @@ type LoadableCache[T any] struct {
 	loadFunc     LoadFunction[T]
 	cache        CacheInterface[T]
 	setChannel   chan *loadableKeyValue[T]
+	setCache     sync.Map
 	setterWg     *sync.WaitGroup
 }
 
@@ -55,6 +56,7 @@ func (c *LoadableCache[T]) setter() {
 
 		cacheKey := c.getCacheKey(item.key)
 		c.singleFlight.Forget(cacheKey)
+		c.setCache.Delete(cacheKey)
 	}
 }
 
@@ -69,6 +71,9 @@ func (c *LoadableCache[T]) Get(ctx context.Context, key any) (T, error) {
 
 	// Unable to find in cache, try to load it from load function
 	cacheKey := c.getCacheKey(key)
+	if v, ok := c.setCache.Load(cacheKey); ok {
+		return v.(T), nil
+	}
 	zero := *new(T)
 
 	loadedResult, err, _ := c.singleFlight.Do(
@@ -89,6 +94,7 @@ func (c *LoadableCache[T]) Get(ctx context.Context, key any) (T, error) {
 	}
 
 	// Then, put it back in cache
+	c.setCache.Store(cacheKey, object)
 	c.setChannel <- &loadableKeyValue[T]{key, object}
 
 	return object, err

lib/cache/loadable_test.go

@@ -8,6 +8,7 @@ import (
 	"testing"
 	"time"
 
+	"github.com/eko/gocache/lib/v4/store"
 	"github.com/stretchr/testify/assert"
 	"go.uber.org/mock/gomock"
 )
@@ -299,3 +300,29 @@ func TestLoadableGetType(t *testing.T) {
 	// When - Then
 	assert.Equal(t, LoadableType, cache.GetType())
 }
+
+func TestLoadableGetTwice(t *testing.T) {
+	// Given
+	ctrl := gomock.NewController(t)
+
+	cache1 := NewMockSetterCacheInterface[any](ctrl)
+
+	var counter atomic.Uint64
+	loadFunc := func(_ context.Context, key any) (any, error) {
+		return counter.Add(1), nil
+	}
+
+	cache := NewLoadable[any](loadFunc, cache1)
+
+	key := 1
+	cache1.EXPECT().Get(context.Background(), key).Return(nil, store.NotFound{}).Times(2)
+	cache1.EXPECT().Set(context.Background(), key, uint64(1)).Times(1)
+	v1, err1 := cache.Get(context.Background(), key)
+	v2, err2 := cache.Get(context.Background(), key) // setter may not be called now because it's done by another goroutine
+	assert.NoError(t, err1)
+	assert.NoError(t, err2)
+	assert.Equal(t, uint64(1), v1)
+	assert.Equal(t, uint64(1), v2)
+	assert.Equal(t, uint64(1), counter.Load())
+	_ = cache.Close() // wait for setter
+}