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server: clarify documentation around setting and sending headers and ServerStream errors (#5302)

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Doug Fawley 2022-04-08 13:11:40 -07:00 committed by GitHub
parent 924e4849c5
commit 9711b148c4
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2 changed files with 36 additions and 10 deletions
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40
server.go
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@ -1801,12 +1801,26 @@ func (s *Server) getCodec(contentSubtype string) baseCodec {
return codec
}
// SetHeader sets the header metadata.
// When called multiple times, all the provided metadata will be merged.
// All the metadata will be sent out when one of the following happens:
// - grpc.SendHeader() is called;
// - The first response is sent out;
// - An RPC status is sent out (error or success).
// SetHeader sets the header metadata to be sent from the server to the client.
// The context provided must be the context passed to the server's handler.
//
// Streaming RPCs should prefer the SetHeader method of the ServerStream.
//
// When called multiple times, all the provided metadata will be merged. All
// the metadata will be sent out when one of the following happens:
//
// - grpc.SendHeader is called, or for streaming handlers, stream.SendHeader.
// - The first response message is sent. For unary handlers, this occurs when
// the handler returns; for streaming handlers, this can happen when stream's
// SendMsg method is called.
// - An RPC status is sent out (error or success). This occurs when the handler
// returns.
//
// SetHeader will fail if called after any of the events above.
//
// The error returned is compatible with the status package. However, the
// status code will often not match the RPC status as seen by the client
// application, and therefore, should not be relied upon for this purpose.
func SetHeader(ctx context.Context, md metadata.MD) error {
if md.Len() == 0 {
return nil
@ -1818,8 +1832,14 @@ func SetHeader(ctx context.Context, md metadata.MD) error {
return stream.SetHeader(md)
}
// SendHeader sends header metadata. It may be called at most once.
// The provided md and headers set by SetHeader() will be sent.
// SendHeader sends header metadata. It may be called at most once, and may not
// be called after any event that causes headers to be sent (see SetHeader for
// a complete list). The provided md and headers set by SetHeader() will be
// sent.
//
// The error returned is compatible with the status package. However, the
// status code will often not match the RPC status as seen by the client
// application, and therefore, should not be relied upon for this purpose.
func SendHeader(ctx context.Context, md metadata.MD) error {
stream := ServerTransportStreamFromContext(ctx)
if stream == nil {
@ -1833,6 +1853,10 @@ func SendHeader(ctx context.Context, md metadata.MD) error {
// SetTrailer sets the trailer metadata that will be sent when an RPC returns.
// When called more than once, all the provided metadata will be merged.
//
// The error returned is compatible with the status package. However, the
// status code will often not match the RPC status as seen by the client
// application, and therefore, should not be relied upon for this purpose.
func SetTrailer(ctx context.Context, md metadata.MD) error {
if md.Len() == 0 {
return nil

6
stream.go
View File

@ -1370,8 +1370,10 @@ func (as *addrConnStream) finish(err error) {
// ServerStream defines the server-side behavior of a streaming RPC.
//
// All errors returned from ServerStream methods are compatible with the
// status package.
// Errors returned from ServerStream methods are compatible with the status
// package. However, the status code will often not match the RPC status as
// seen by the client application, and therefore, should not be relied upon for
// this purpose.
type ServerStream interface {
// SetHeader sets the header metadata. It may be called multiple times.
// When call multiple times, all the provided metadata will be merged.