metadata: add content lease on existing content

When a writer is requested for an object that already
exists, add that object to the provided any lease to prevent
other operations from affecting the current lease's use of
that content.

Signed-off-by: Derek McGowan <derek@mcgstyle.net>

metadata/db_test.go

@@ -10,6 +10,7 @@ import (
 	"os"
 	"path/filepath"
 	"runtime/pprof"
+	"strings"
 	"testing"
 	"time"
 
@@ -29,6 +30,44 @@ import (
 	"github.com/pkg/errors"
 )
 
+func testDB(t *testing.T) (context.Context, *DB, func()) {
+	ctx, cancel := context.WithCancel(context.Background())
+	ctx = namespaces.WithNamespace(ctx, "testing")
+
+	dirname, err := ioutil.TempDir("", strings.Replace(t.Name(), "/", "_", -1)+"-")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	snapshotter, err := naive.NewSnapshotter(filepath.Join(dirname, "naive"))
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	cs, err := local.NewStore(filepath.Join(dirname, "content"))
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	bdb, err := bolt.Open(filepath.Join(dirname, "metadata.db"), 0644, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	db := NewDB(bdb, cs, map[string]snapshots.Snapshotter{"naive": snapshotter})
+	if err := db.Init(ctx); err != nil {
+		t.Fatal(err)
+	}
+
+	return ctx, db, func() {
+		bdb.Close()
+		if err := os.RemoveAll(dirname); err != nil {
+			t.Log("failed removing temp dir", err)
+		}
+		cancel()
+	}
+}
+
 func TestInit(t *testing.T) {
 	ctx, db, cancel := testEnv(t)
 	defer cancel()