add garbage collector for database cache

pkg/infra/distcache/database_storage.go

@@ -3,18 +3,48 @@ package distcache
 import (
 	"time"
 
+	"github.com/grafana/grafana/pkg/log"
 	"github.com/grafana/grafana/pkg/services/sqlstore"
 )
 
 type databaseCache struct {
 	SQLStore *sqlstore.SqlStore
+	log      log.Logger
+}
+
+func newDatabaseCache(sqlstore *sqlstore.SqlStore) *databaseCache {
+	dc := &databaseCache{
+		SQLStore: sqlstore,
+		log:      log.New("distcache.database"),
+	}
+
+	go dc.StartGC()
+	return dc
 }
 
 var getTime = time.Now
 
-func (dc *databaseCache) Get(key string) (interface{}, error) {
-	//now := getTime().Unix()
+func (dc *databaseCache) internalRunGC() {
+	now := getTime().Unix()
+	sql := `DELETE FROM cache_data WHERE (? - created) >= expire`
 
+	//EXTRACT(EPOCH FROM NOW()) - created >= expire
+	//UNIX_TIMESTAMP(NOW()) - created >= expire
+	_, err := dc.SQLStore.NewSession().Exec(sql, now)
+	if err != nil {
+		dc.log.Error("failed to run garbage collect", "error", err)
+	}
+}
+
+func (dc *databaseCache) StartGC() {
+	dc.internalRunGC()
+
+	time.AfterFunc(time.Second*10, func() {
+		dc.StartGC()
+	})
+}
+
+func (dc *databaseCache) Get(key string) (interface{}, error) {
 	cacheHits := []CacheData{}
 	err := dc.SQLStore.NewSession().Where(`key = ?`, key).Find(&cacheHits)
 	if err != nil {
@@ -65,7 +95,7 @@ func (dc *databaseCache) Put(key string, value interface{}, expire int64) error
 	}
 
 	if len(cacheHits) > 0 {
-		_, err = dc.SQLStore.NewSession().Exec("UPDATE cached_data SET data=?, created=?, expire=? WHERE key=?", data, now, expire, key)
+		_, err = dc.SQLStore.NewSession().Exec("UPDATE cache_data SET data=?, created=?, expire=? WHERE key=?", data, now, expire, key)
 	} else {
 		_, err = dc.SQLStore.NewSession().Exec("INSERT INTO cache_data(key,data,created_at,expires) VALUES(?,?,?,?)", key, data, now, expire)
 	}

pkg/infra/distcache/database_storage_test.go

@@ -0,0 +1,50 @@
+package distcache
+
+import (
+	"testing"
+	"time"
+
+	"github.com/bmizerany/assert"
+
+	"github.com/grafana/grafana/pkg/log"
+	"github.com/grafana/grafana/pkg/services/sqlstore"
+)
+
+func TestDatabaseStorageGarbageCollection(t *testing.T) {
+	sqlstore := sqlstore.InitTestDB(t)
+
+	db := &databaseCache{
+		SQLStore: sqlstore,
+		log:      log.New("distcache.database"),
+	}
+
+	obj := &CacheableStruct{String: "foolbar"}
+
+	//set time.now to 2 weeks ago
+	getTime = func() time.Time { return time.Now().AddDate(0, 0, -2) }
+	db.Put("key1", obj, 1000)
+	db.Put("key2", obj, 1000)
+	db.Put("key3", obj, 1000)
+
+	// insert object that should never expire
+	db.Put("key4", obj, 0)
+
+	getTime = time.Now
+	db.Put("key5", obj, 1000)
+
+	//run GC
+	db.internalRunGC()
+
+	//try to read values
+	_, err := db.Get("key1")
+	assert.Equal(t, err, ErrCacheItemNotFound)
+	_, err = db.Get("key2")
+	assert.Equal(t, err, ErrCacheItemNotFound)
+	_, err = db.Get("key3")
+	assert.Equal(t, err, ErrCacheItemNotFound)
+
+	_, err = db.Get("key4")
+	assert.Equal(t, err, nil)
+	_, err = db.Get("key5")
+	assert.Equal(t, err, nil)
+}