Local cache to reuse db connection (#40)

migrate library not closing the db connection db show those connections
are in 'idle' state. When the count reaches the limit database is not
accessible.

so cache the db connection in a map with resouce name as key.

atlas-db-controller/databaseSchemaResource.go

@@ -4,6 +4,7 @@ import (
 	"fmt"
 
 	"github.com/golang-migrate/migrate"
+	"github.com/golang-migrate/migrate/database"
 	"github.com/golang/glog"
 	atlas "github.com/infobloxopen/atlas-db/pkg/apis/db/v1alpha1"
 	"k8s.io/apimachinery/pkg/api/errors"
@@ -12,6 +13,8 @@ import (
 	"k8s.io/client-go/tools/cache"
 )
 
+var dbDriverMap = make(map[string]database.Driver)
+
 func (c *Controller) syncSchema(key string) error {
 	glog.Infof("Schema key: %v", key)
 
@@ -116,15 +119,29 @@ func (c *Controller) syncSchema(key string) error {
 		}
 	}
 
-	mgrt, err := migrate.New(gitURL, dsn)
+	// migrate package is not closing the dbconnnection so using a local cache reuse dbconnection.
+	// TODO when same resource with different dsn arrives; need to unset local cache during schema resource deletion.
+	dbDriver, ok := dbDriverMap[schema.Namespace+schema.Name]
+	if !ok {
+		dbDriver, err = database.Open(dsn)
+		if err != nil {
+			schemaStatusMsg = fmt.Sprintf("failed to open dbconnection: %s", err)
+			c.updateDatabaseSchemaStatus(key, schema, StateError, schemaStatusMsg)
+			err = fmt.Errorf(schemaStatusMsg)
+			runtime.HandleError(err)
+			return err
+		}
+		dbDriverMap[schema.Namespace+schema.Name] = dbDriver
+	}
+
+	mgrt, err := migrate.NewWithDatabaseInstance(gitURL, dbName, dbDriver)
 	if err != nil {
 		schemaStatusMsg = fmt.Sprintf("failed to initialize migrate engine: %s", err)
 		c.updateDatabaseSchemaStatus(key, schema, StateError, schemaStatusMsg)
 		err = fmt.Errorf(schemaStatusMsg)
 		runtime.HandleError(err)
 		return err
 	}
-	defer mgrt.Close()
 
 	ver, dirt, err := mgrt.Version()
 	if err != nil {