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- // Copyright 2016 Google LLC
- //
- // Licensed under the Apache License, Version 2.0 (the "License");
- // you may not use this file except in compliance with the License.
- // You may obtain a copy of the License at
- //
- // http://www.apache.org/licenses/LICENSE-2.0
- //
- // Unless required by applicable law or agreed to in writing, software
- // distributed under the License is distributed on an "AS IS" BASIS,
- // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- // See the License for the specific language governing permissions and
- // limitations under the License.
-
- package internal
-
- // This file contains the server implementation of Bytestream declared at:
- // https://github.com/googleapis/googleapis/blob/master/google/bytestream/bytestream.proto
- //
- // Bytestream uses bidirectional streaming (http://grpc.io/docs/guides/concepts.html#bidirectional-streaming-rpc).
-
- import (
- "context"
- "fmt"
- "io"
-
- "google.golang.org/grpc"
- "google.golang.org/grpc/codes"
-
- pb "google.golang.org/genproto/googleapis/bytestream"
- )
-
- // ReadHandler reads from the Bytestream.
- // Note: error returns must return an instance of grpc.rpcError unless otherwise handled in grpc-go/rpc_util.go.
- // http://google.golang.org/grpc provides Errorf(code, fmt, ...) to create instances of grpc.rpcError.
- // Note: Cancelling the context will abort the stream ("drop the connection"). Consider returning a non-nil error instead.
- type ReadHandler interface {
- // GetReader provides an io.ReaderAt, which will not be retained by the Server after the pb.ReadRequest.
- GetReader(ctx context.Context, name string) (io.ReaderAt, error)
- // Close does not have to do anything, but is here for if the io.ReaderAt wants to call Close().
- Close(ctx context.Context, name string) error
- }
-
- // WriteHandler handles writes from the Bytestream. For example:
- // Note: error returns must return an instance of grpc.rpcError unless otherwise handled in grpc-go/rpc_util.go.
- // grpc-go/rpc_util.go provides the helper func Errorf(code, fmt, ...) to create instances of grpc.rpcError.
- // Note: Cancelling the context will abort the stream ("drop the connection"). Consider returning a non-nil error instead.
- type WriteHandler interface {
- // GetWriter provides an io.Writer that is ready to write at initOffset.
- // The io.Writer will not be retained by the Server after the pb.WriteRequest.
- GetWriter(ctx context.Context, name string, initOffset int64) (io.Writer, error)
- // Close does not have to do anything, but is related to Server.AllowOverwrite. Or if the io.Writer simply wants a Close() call.
- // Close is called when the server receives a pb.WriteRequest with finish_write = true.
- // If Server.AllowOverwrite == true then Close() followed by GetWriter() for the same name indicates the name is being overwritten, even if the initOffset is different.
- Close(ctx context.Context, name string) error
- }
-
- // Internal service that implements pb.ByteStreamServer. Because the methods Write() and Read() are exported for grpc to link against,
- // grpcService is deliberately not exported so go code cannot call grpcService.Write() or grpcService.Read().
- type grpcService struct {
- parent *Server
- }
-
- // Server wraps the RPCs in pb. Use bytestream.NewServer() to create a Server.
- type Server struct {
- status map[string]*pb.QueryWriteStatusResponse
- readHandler ReadHandler
- writeHandler WriteHandler
- rpc *grpcService
-
- // AllowOverwrite controls Server behavior when a WriteRequest with finish_write = true is followed by another WriteRequest.
- AllowOverwrite bool
-
- // Bytestream allows a WriteRequest to omit the resource name, in which case it will be appended to the last WriteRequest.
- LastWrittenResource string
- }
-
- // NewServer creates a new bytestream.Server using gRPC.
- // gsrv is the *grpc.Server this bytestream.Server will listen on.
- // readHandler handles any incoming pb.ReadRequest or nil which means all pb.ReadRequests will be rejected.
- // writeHandler handles any incoming pb.WriteRequest or nil which means all pb.WriteRequests will be rejected.
- // readHandler and writeHandler cannot both be nil.
- func NewServer(gsrv *grpc.Server, readHandler ReadHandler, writeHandler WriteHandler) (*Server, error) {
- if readHandler == nil && writeHandler == nil {
- return nil, fmt.Errorf("readHandler and writeHandler cannot both be nil")
- }
-
- server := &Server{
- status: make(map[string]*pb.QueryWriteStatusResponse),
- readHandler: readHandler,
- writeHandler: writeHandler,
- rpc: &grpcService{},
- }
- server.rpc.parent = server
-
- // Register a server.
- pb.RegisterByteStreamServer(gsrv, server.rpc)
-
- return server, nil
- }
-
- // Write handles the pb.ByteStream_WriteServer and sends a pb.WriteResponse
- // Implements bytestream.proto "rpc Write(stream WriteRequest) returns (WriteResponse)".
- func (rpc *grpcService) Write(stream pb.ByteStream_WriteServer) error {
- for {
- writeReq, err := stream.Recv()
- if err == io.EOF {
- // io.EOF errors are a non-error for the Write() caller.
- return nil
- } else if err != nil {
- return grpc.Errorf(codes.Unknown, "stream.Recv() failed: %v", err)
- }
- if rpc.parent.writeHandler == nil {
- return grpc.Errorf(codes.Unimplemented, "instance of NewServer(writeHandler = nil) rejects all writes")
- }
-
- status, ok := rpc.parent.status[writeReq.ResourceName]
- if !ok {
- // writeReq.ResourceName is a new resource name.
- if writeReq.ResourceName == "" {
- return grpc.Errorf(codes.InvalidArgument, "WriteRequest: empty or missing resource_name")
- }
- status = &pb.QueryWriteStatusResponse{
- CommittedSize: writeReq.WriteOffset,
- }
- rpc.parent.status[writeReq.ResourceName] = status
- } else {
- // writeReq.ResourceName has already been seen by this server.
- if status.Complete {
- if !rpc.parent.AllowOverwrite {
- return grpc.Errorf(codes.InvalidArgument, "%q finish_write = true already, got %d byte WriteRequest and Server.AllowOverwrite = false",
- writeReq.ResourceName, len(writeReq.Data))
- }
- // Truncate the resource stream.
- status.Complete = false
- status.CommittedSize = writeReq.WriteOffset
- }
- }
-
- if writeReq.WriteOffset != status.CommittedSize {
- return grpc.Errorf(codes.FailedPrecondition, "%q write_offset=%d differs from server internal committed_size=%d",
- writeReq.ResourceName, writeReq.WriteOffset, status.CommittedSize)
- }
-
- // WriteRequest with empty data is ok.
- if len(writeReq.Data) != 0 {
- writer, err := rpc.parent.writeHandler.GetWriter(stream.Context(), writeReq.ResourceName, status.CommittedSize)
- if err != nil {
- return grpc.Errorf(codes.Internal, "GetWriter(%q): %v", writeReq.ResourceName, err)
- }
- wroteLen, err := writer.Write(writeReq.Data)
- if err != nil {
- return grpc.Errorf(codes.Internal, "Write(%q): %v", writeReq.ResourceName, err)
- }
- status.CommittedSize += int64(wroteLen)
- }
-
- if writeReq.FinishWrite {
- r := &pb.WriteResponse{CommittedSize: status.CommittedSize}
- // Note: SendAndClose does NOT close the server stream.
- if err = stream.SendAndClose(r); err != nil {
- return grpc.Errorf(codes.Internal, "stream.SendAndClose(%q, WriteResponse{ %d }): %v", writeReq.ResourceName, status.CommittedSize, err)
- }
- status.Complete = true
- if status.CommittedSize == 0 {
- return grpc.Errorf(codes.FailedPrecondition, "writeHandler.Close(%q): 0 bytes written", writeReq.ResourceName)
- }
- if err = rpc.parent.writeHandler.Close(stream.Context(), writeReq.ResourceName); err != nil {
- return grpc.Errorf(codes.Internal, "writeHandler.Close(%q): %v", writeReq.ResourceName, err)
- }
- }
- }
- }
-
- // QueryWriteStatus implements bytestream.proto "rpc QueryWriteStatus(QueryWriteStatusRequest) returns (QueryWriteStatusResponse)".
- // QueryWriteStatus returns the CommittedSize known to the server.
- func (rpc *grpcService) QueryWriteStatus(ctx context.Context, request *pb.QueryWriteStatusRequest) (*pb.QueryWriteStatusResponse, error) {
- s, ok := rpc.parent.status[request.ResourceName]
- if !ok {
- return nil, grpc.Errorf(codes.NotFound, "resource_name not found: QueryWriteStatusRequest %v", request)
- }
- return s, nil
- }
-
- func (rpc *grpcService) readFrom(request *pb.ReadRequest, reader io.ReaderAt, stream pb.ByteStream_ReadServer) error {
- limit := int(request.ReadLimit)
- if limit < 0 {
- return grpc.Errorf(codes.InvalidArgument, "Read(): read_limit=%d is invalid", limit)
- }
- offset := request.ReadOffset
- if offset < 0 {
- return grpc.Errorf(codes.InvalidArgument, "Read(): offset=%d is invalid", offset)
- }
-
- var buf []byte
- if limit > 0 {
- buf = make([]byte, limit)
- } else {
- buf = make([]byte, 1024*1024) // 1M buffer is reasonable.
- }
- bytesSent := 0
- for limit == 0 || bytesSent < limit {
- n, err := reader.ReadAt(buf, offset)
- if n > 0 {
- if err := stream.Send(&pb.ReadResponse{Data: buf[:n]}); err != nil {
- return grpc.Errorf(grpc.Code(err), "Send(resourceName=%q offset=%d): %v", request.ResourceName, offset, grpc.ErrorDesc(err))
- }
- } else if err == nil {
- return grpc.Errorf(codes.Internal, "nil error on empty read: io.ReaderAt contract violated")
- }
- offset += int64(n)
- bytesSent += n
- if err == io.EOF {
- break
- }
- if err != nil {
- return grpc.Errorf(codes.Unknown, "ReadAt(resourceName=%q offset=%d): %v", request.ResourceName, offset, err)
- }
- }
- return nil
- }
-
- // Read handles a pb.ReadRequest sending bytes to the pb.ByteStream_ReadServer
- // Implements bytestream.proto "rpc Read(ReadRequest) returns (stream ReadResponse)"
- func (rpc *grpcService) Read(request *pb.ReadRequest, stream pb.ByteStream_ReadServer) error {
- if rpc.parent.readHandler == nil {
- return grpc.Errorf(codes.Unimplemented, "instance of NewServer(readHandler = nil) rejects all reads")
- }
- if request == nil {
- return grpc.Errorf(codes.Internal, "Read(ReadRequest == nil)")
- }
- if request.ResourceName == "" {
- return grpc.Errorf(codes.InvalidArgument, "ReadRequest: empty or missing resource_name")
- }
-
- reader, err := rpc.parent.readHandler.GetReader(stream.Context(), request.ResourceName)
- if err != nil {
- return err
- }
- if err = rpc.readFrom(request, reader, stream); err != nil {
- rpc.parent.readHandler.Close(stream.Context(), request.ResourceName)
- return err
- }
- if err = rpc.parent.readHandler.Close(stream.Context(), request.ResourceName); err != nil {
- return err
- }
- return nil
- }
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