go/runtime/client: use history for GetBlock(latest)

.changelog/2795.bugfix.md

@@ -0,0 +1,5 @@
+go/runtime/client: use history for GetBlock(latest)
+
+Using history for all GetBlock requests prevents the case where the latest
+block would already be available but not yet in history, leading to
+inconsistent results if querying by specific block number.

go/roothash/api/history.go

@@ -32,4 +32,7 @@ type BlockHistory interface {
 
 	// GetBlock returns the block at a specific round.
 	GetBlock(ctx context.Context, round uint64) (*block.Block, error)
+
+	// GetLatestBlock returns the block at latest round.
+	GetLatestBlock(ctx context.Context) (*block.Block, error)
 }

go/runtime/client/client.go

@@ -216,16 +216,17 @@ func (c *runtimeClient) WatchBlocks(ctx context.Context, runtimeID common.Namesp
 
 // Implements api.RuntimeClient.
 func (c *runtimeClient) GetBlock(ctx context.Context, request *api.GetBlockRequest) (*block.Block, error) {
-	if request.Round == api.RoundLatest {
-		return c.common.consensus.RootHash().GetLatestBlock(ctx, request.RuntimeID, consensus.HeightLatest)
-	}
-
 	rt, err := c.common.runtimeRegistry.GetRuntime(request.RuntimeID)
 	if err != nil {
 		return nil, err
 	}
 
-	return rt.History().GetBlock(ctx, request.Round)
+	switch request.Round {
+	case api.RoundLatest:
+		return rt.History().GetLatestBlock(ctx)
+	default:
+		return rt.History().GetBlock(ctx, request.Round)
+	}
 }
 
 func (c *runtimeClient) getTxnTree(blk *block.Block) *transaction.Tree {

go/runtime/client/tests/tester.go

@@ -83,6 +83,10 @@ func testQuery(
 	require.NoError(t, err, "GetBlock")
 	require.EqualValues(t, 4, blk.Header.Round)
 
+	blkLatest, err := c.GetBlock(ctx, &api.GetBlockRequest{RuntimeID: runtimeID, Round: api.RoundLatest})
+	require.NoError(t, err, "GetBlock(RoundLatest)")
+	require.EqualValues(t, 4, blkLatest.Header.Round)
+
 	// Out of bounds block round.
 	_, err = c.GetBlock(ctx, &api.GetBlockRequest{RuntimeID: runtimeID, Round: 5})
 	require.Error(t, err, "GetBlock")

go/runtime/history/history.go

@@ -76,6 +76,10 @@ func (h *nopHistory) GetBlock(ctx context.Context, round uint64) (*block.Block,
 	return nil, errNopHistory
 }
 
+func (h *nopHistory) GetLatestBlock(ctx context.Context) (*block.Block, error) {
+	return nil, errNopHistory
+}
+
 func (h *nopHistory) Pruner() Pruner {
 	pruner, _ := NewNonePruner()(nil)
 	return pruner
@@ -144,6 +148,19 @@ func (h *runtimeHistory) GetBlock(ctx context.Context, round uint64) (*block.Blo
 	return annBlk.Block, nil
 }
 
+func (h *runtimeHistory) GetLatestBlock(ctx context.Context) (*block.Block, error) {
+	meta, err := h.db.metadata()
+	if err != nil {
+		return nil, err
+	}
+	annBlk, err := h.db.getBlock(meta.LastRound)
+	if err != nil {
+		return nil, err
+	}
+
+	return annBlk.Block, nil
+}
+
 func (h *runtimeHistory) Pruner() Pruner {
 	return h.pruner
 }

go/runtime/history/history_test.go

@@ -41,6 +41,10 @@ func TestHistory(t *testing.T) {
 	require.Error(err, "GetBlock should fail for non-indexed block")
 	require.Equal(roothash.ErrNotFound, err)
 
+	_, err = history.GetLatestBlock(context.Background())
+	require.Error(err, "GetLatestBlock should fail for no indexed block")
+	require.Equal(roothash.ErrNotFound, err)
+
 	err = history.ConsensusCheckpoint(42)
 	require.NoError(err, "ConsensusCheckpoint")
 	err = history.ConsensusCheckpoint(40)
@@ -82,6 +86,10 @@ func TestHistory(t *testing.T) {
 	require.NoError(err, "GetBlock")
 	require.Equal(&putBlk, gotBlk, "GetBlock should return the correct block")
 
+	gotLatestBlk, err := history.GetLatestBlock(context.Background())
+	require.NoError(err, "GetLatestBlock")
+	require.Equal(&putBlk, gotLatestBlk, "GetLatestBlock should return the correct block")
+
 	// Close history and try to reopen and continue.
 	history.Close()
 
@@ -102,6 +110,10 @@ func TestHistory(t *testing.T) {
 	gotBlk, err = history.GetBlock(context.Background(), 10)
 	require.NoError(err, "GetBlock")
 	require.Equal(&putBlk, gotBlk, "GetBlock should return the correct block")
+
+	gotLatestBlk, err = history.GetLatestBlock(context.Background())
+	require.NoError(err, "GetLatestBlock")
+	require.Equal(&putBlk, gotLatestBlk, "GetLatestBlock should return the correct block")
 }
 
 type testPruneHandler struct {