hook: Stop transactions on pre-receive hook failure

The pre-receive hook business logic is only executed on primary nodes in
order to avoid executing custom hooks and the likes multiple times.
Failures of the pre-receive hook e.g. because of a denied access will
thus only ever be detected on primaries. While correct, this has
unfortunate side effects when transactions come into play. As the
primary will not vote on such a transaction, secondaries will wait for
quorum and eventually time out as the primary is never going to cast its
own vote. While the end result is the same as the transaction has
failed, it will raise a misleading error message and cause a delay of 10
seconds.

With our newly grown ability to stop transactions, we can now do better:
in case the pre-receive hook declines the push, we can now gracefully
stop the transaction. As a result, secondaries will know to abort and
not make a big fuzz about it.

2 files changed, 22 insertions, 1 deletions

diff --git a/internal/gitaly/hook/prereceive.go b/internal/gitaly/hook/prereceive.go
index 8f8fa79cf..2754b572d 100644
--- a/internal/gitaly/hook/prereceive.go
+++ b/internal/gitaly/hook/prereceive.go
@@ -53,6 +53,9 @@ func (m *GitLabHookManager) PreReceiveHook(ctx context.Context, repo *gitalypb.R
 	// Only the primary should execute hooks and increment reference counters.
 	if primary {
 		if err := m.preReceiveHook(ctx, repo, env, changes, stdout, stderr); err != nil {
+			// If the pre-receive hook declines the push, then we need to stop any
+			// secondaries voting on the transaction.
+			m.stopTransaction(ctx, env)
 			return err
 		}
 	}
diff --git a/internal/gitaly/hook/transactions.go b/internal/gitaly/hook/transactions.go
index 34b6b758c..6d52ebf9d 100644
--- a/internal/gitaly/hook/transactions.go
+++ b/internal/gitaly/hook/transactions.go
@@ -87,8 +87,26 @@ func (m *GitLabHookManager) voteOnTransaction(ctx context.Context, hash []byte,
 			return err
 		}
 
-		if response.State != gitalypb.VoteTransactionResponse_COMMIT {
+		switch response.State {
+		case gitalypb.VoteTransactionResponse_COMMIT:
+			return nil
+		case gitalypb.VoteTransactionResponse_ABORT:
 			return errors.New("transaction was aborted")
+		case gitalypb.VoteTransactionResponse_STOP:
+			return errors.New("transaction was stopped")
+		default:
+			return errors.New("invalid transaction state")
+		}
+	})
+}
+
+func (m *GitLabHookManager) stopTransaction(ctx context.Context, env []string) error {
+	return m.runWithTransaction(ctx, env, func(ctx context.Context, tx metadata.Transaction, client gitalypb.RefTransactionClient) error {
+		_, err := client.StopTransaction(ctx, &gitalypb.StopTransactionRequest{
+			TransactionId: tx.ID,
+		})
+		if err != nil {
+			return err
 		}
 
 		return nil