Merge pull request #3 from pamburus/feature/try-lock

new: TryLock

discard_vault.go

@@ -14,5 +14,9 @@ func (v *discardVault) Lock(context.Context, Tx) error {
 	return nil
 }
 
+func (v *discardVault) TryLock(context.Context, Tx) (bool, error) {
+	return true, nil
+}
+
 func (v *discardVault) Unlock(Tx) {
 }

stl.go

@@ -31,5 +31,6 @@ type Builder interface {
 // the specified transaction.
 type Vault interface {
 	Lock(context.Context, Tx) error
+	TryLock(context.Context, Tx) (bool, error)
 	Unlock(Tx)
 }

stl_test.go

@@ -372,3 +372,27 @@ func TestMergeTx(t *testing.T) {
 	require.ElementsMatch(t, expectedExs, tx.ListExclusive())
 	require.ElementsMatch(t, expectedShs, tx.ListShared())
 }
+
+func TestTryLock(t *testing.T) {
+	v := NewVault()
+	tx1 := NewStacked().Shared("resource1").ToTx()
+	ok, err := v.TryLock(context.Background(), tx1)
+	require.NoError(t, err)
+	require.True(t, ok)
+	defer v.Unlock(tx1)
+
+	tx2 := NewStacked().Exclusive("resource1").ToTx()
+	ok, err = v.TryLock(context.Background(), tx2)
+	require.NoError(t, err)
+	require.False(t, ok)
+}
+
+func TestDiscardVault(t *testing.T) {
+	v := NewDiscardVault()
+	err := v.Lock(context.Background(), nil)
+	require.NoError(t, err)
+	v.Unlock(nil)
+	ok, err := v.TryLock(context.Background(), nil)
+	require.NoError(t, err)
+	require.True(t, ok)
+}

vault.go

@@ -35,6 +35,11 @@ func (v *vault) Lock(ctx context.Context, tx Tx) error {
 	}
 }
 
+// TryLock tries to lock the resources according to specified Tx.
+func (v *vault) TryLock(ctx context.Context, tx Tx) (bool, error) {
+	return v.tryLock(tx) == nil, nil
+}
+
 // Unlock unlocks the resources according to specified Tx.
 func (v *vault) Unlock(tx Tx) {
 	v.mu.Lock()