cometbft · thanethomson · Aug 7, 2023 · Aug 4, 2023 · Aug 4, 2023 · Aug 4, 2023
diff --git a/proto/tendermint/services/block/v1/block.pb.go b/proto/tendermint/services/block/v1/block.pb.go
diff --git a/proto/tendermint/services/block/v1/block.proto b/proto/tendermint/services/block/v1/block.proto
@@ -16,10 +16,16 @@ message GetByHeightResponse {
   tendermint.types.Block   block    = 2;
 }
 
-// GetLatestHeightRequest - empty message since no parameter is required
-message GetLatestHeightRequest {
+message GetLatestRequest {}
+
+message GetLatestResponse {
+  tendermint.types.BlockID block_id = 1;
+  tendermint.types.Block   block    = 2;
 }
 
+// GetLatestHeightRequest - empty message since no parameter is required
+message GetLatestHeightRequest {}
+
 // GetLatestHeightResponse provides the height of the latest committed block.
 message GetLatestHeightResponse {
   // The height of the latest committed block. Will be 0 if no data has been

diff --git a/proto/tendermint/services/block/v1/block_service.pb.go b/proto/tendermint/services/block/v1/block_service.pb.go
diff --git a/proto/tendermint/services/block/v1/block_service.proto b/proto/tendermint/services/block/v1/block_service.proto
@@ -7,10 +7,12 @@ import "tendermint/services/block/v1/block.proto";
 
 // BlockService provides information about blocks
 service BlockService {
-  // GetBlock retrieves the block information at a particular height,
-  // if height '0' (zero) is specified it returns the latest height
+  // GetBlock retrieves the block information at a particular height.
   rpc GetByHeight(GetByHeightRequest) returns (GetByHeightResponse);
 
+  // GetLatest retrieves the latest block.
+  rpc GetLatest(GetLatestRequest) returns (GetLatestResponse);
+
   // GetLatestHeight returns a stream of the latest block heights committed by
   // the network. This is a long-lived stream that is only terminated by the
   // server if an error occurs. The caller is expected to handle such

diff --git a/rpc/grpc/client/block_service.go b/rpc/grpc/client/block_service.go
@@ -5,14 +5,32 @@ import (
 	"fmt"
 
 	blocksvc "github.com/cometbft/cometbft/proto/tendermint/services/block/v1"
+	cmtproto "github.com/cometbft/cometbft/proto/tendermint/types"
 	"github.com/cometbft/cometbft/types"
 	"github.com/cosmos/gogoproto/grpc"
 )
 
 // Block data returned by the CometBFT BlockService gRPC API.
 type Block struct {
-	BlockID types.BlockID `json:"block_id"`
-	Block   *types.Block  `json:"block"`
+	BlockID *types.BlockID `json:"block_id"`
+	Block   *types.Block   `json:"block"`
+}
+
+func blockFromProto(pblockID *cmtproto.BlockID, pblock *cmtproto.Block) (*Block, error) {
+	blockID, err := types.BlockIDFromProto(pblockID)
+	if err != nil {
+		return nil, err
+	}
+
+	block, err := types.BlockFromProto(pblock)
+	if err != nil {
+		return nil, err
+	}
+
+	return &Block{
+		BlockID: blockID,
+		Block:   block,
+	}, nil
 }
 
 // LatestHeightResult type used in GetLatestResult and send to the client
@@ -22,12 +40,32 @@ type LatestHeightResult struct {
 	Error  error
 }
 
+type getLatestHeightConfig struct {
+	chSize uint
+}
+
+type GetLatestHeightOption func(*getLatestHeightConfig)
+
+// GetLatestHeightChannelSize allows control over the channel size. If not used
+// or the channel size is set to 0, an unbuffered channel will be created.
+func GetLatestHeightChannelSize(sz uint) GetLatestHeightOption {
+	return func(opts *getLatestHeightConfig) {
+		opts.chSize = sz
+	}
+}
+
 // BlockServiceClient provides block information
 type BlockServiceClient interface {
+	// GetBlockByHeight attempts to retrieve the block associated with the
+	// given height.
 	GetBlockByHeight(ctx context.Context, height int64) (*Block, error)
-	// GetLatestHeight provides sends the latest committed block height to the given output
-	// channel as blocks are committed.
-	GetLatestHeight(ctx context.Context, resultCh chan<- LatestHeightResult)
+
+	// GetLatestBlock attempts to retrieve the latest committed block.
+	GetLatestBlock(ctx context.Context) (*Block, error)
+
+	// GetLatestHeight provides sends the latest committed block height to the
+	// resulting output channel as blocks are committed.
+	GetLatestHeight(ctx context.Context, opts ...GetLatestHeightOption) (<-chan LatestHeightResult, error)
 }
 
 type blockServiceClient struct {
@@ -42,67 +80,67 @@ func newBlockServiceClient(conn grpc.ClientConn) BlockServiceClient {
 
 // GetBlockByHeight implements BlockServiceClient GetBlockByHeight
 func (c *blockServiceClient) GetBlockByHeight(ctx context.Context, height int64) (*Block, error) {
-	req := blocksvc.GetByHeightRequest{
+	res, err := c.client.GetByHeight(ctx, &blocksvc.GetByHeightRequest{
 		Height: height,
-	}
-	res, err := c.client.GetByHeight(ctx, &req)
+	})
 	if err != nil {
 		return nil, err
 	}
 
-	// convert Block from proto to core type
-	block, err := types.BlockFromProto(res.Block)
-	if err != nil {
-		return nil, err
-	}
+	return blockFromProto(res.BlockId, res.Block)
+}
 
-	// convert BlockID from proto to core type
-	blockID, err := types.BlockIDFromProto(res.BlockId)
+// GetLatestBlock implements BlockServiceClient.
+func (c *blockServiceClient) GetLatestBlock(ctx context.Context) (*Block, error) {
+	res, err := c.client.GetLatest(ctx, &blocksvc.GetLatestRequest{})
 	if err != nil {
 		return nil, err
 	}
 
-	response := Block{
-		BlockID: *blockID,
-		Block:   block,
-	}
-	return &response, nil
+	return blockFromProto(res.BlockId, res.Block)
 }
 
 // GetLatestHeight implements BlockServiceClient GetLatestHeight
-// This method provides an out channel (int64) that streams the latest height.
-// The out channel might return non-contiguous heights if the channel becomes full,
-func (c *blockServiceClient) GetLatestHeight(ctx context.Context, resultCh chan<- LatestHeightResult) {
+func (c *blockServiceClient) GetLatestHeight(ctx context.Context, opts ...GetLatestHeightOption) (<-chan LatestHeightResult, error) {
 	req := blocksvc.GetLatestHeightRequest{}
 
 	latestHeightClient, err := c.client.GetLatestHeight(ctx, &req)
 	if err != nil {
-		resultCh <- LatestHeightResult{
-			Height: 0,
-			Error:  fmt.Errorf("error getting a stream for the latest height"),
-		}
+		return nil, fmt.Errorf("error getting a stream for the latest height: %w", err)
+	}
+
+	cfg := &getLatestHeightConfig{}
+	for _, opt := range opts {
+		opt(cfg)
 	}
+	resultCh := make(chan LatestHeightResult, cfg.chSize)
 
 	go func(client blocksvc.BlockService_GetLatestHeightClient) {
+		defer close(resultCh)
 		for {
 			response, err := client.Recv()
 			if err != nil {
-				resultCh <- LatestHeightResult{
-					Height: 0,
-					Error:  fmt.Errorf("error receiving the latest height from a stream"),
+				res := LatestHeightResult{Error: fmt.Errorf("error receiving the latest height from a stream: %w", err)}
+				select {
+				case <-ctx.Done():
+				case resultCh <- res:
 				}
-				break
+				return
 			}
+			res := LatestHeightResult{Height: response.Height}
 			select {
-			case resultCh <- LatestHeightResult{
-				Height: response.Height,
-				Error:  fmt.Errorf("error receiving the latest height from a stream"),
-			}:
+			case <-ctx.Done():
+				return
+			case resultCh <- res:
 			default:
+				// Skip sending this result because the channel is full - the
+				// client will get the next one once the channel opens up again
 			}
 
 		}
 	}(latestHeightClient)
+
+	return resultCh, nil
 }
 
 type disabledBlockServiceClient struct{}
@@ -116,7 +154,12 @@ func (*disabledBlockServiceClient) GetBlockByHeight(context.Context, int64) (*Bl
 	panic("block service client is disabled")
 }
 
+// GetLatestBlock implements BlockServiceClient.
+func (*disabledBlockServiceClient) GetLatestBlock(context.Context) (*Block, error) {
+	panic("block service client is disabled")
+}
+
 // GetLatestHeight implements BlockServiceClient GetLatestHeight - disabled client
-func (*disabledBlockServiceClient) GetLatestHeight(context.Context, chan<- LatestHeightResult) {
+func (*disabledBlockServiceClient) GetLatestHeight(context.Context, ...GetLatestHeightOption) (<-chan LatestHeightResult, error) {
 	panic("block service client is disabled")
 }