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channel: allow discovery of overflown message size.
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Use a dedicated, grpc Status-compatible error to wrap the
unique grpc status code, the size of the rejected message
and the maximum allowed size when a message is rejected
due to size limitations by the sending side.

Signed-off-by: Krisztian Litkey <[email protected]>
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klihub committed Aug 22, 2024
1 parent d8c00df commit 8309e9c
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Showing 2 changed files with 48 additions and 2 deletions.
2 changes: 1 addition & 1 deletion channel.go
Original file line number Diff line number Diff line change
Expand Up @@ -144,7 +144,7 @@ func (ch *channel) recv() (messageHeader, []byte, error) {

func (ch *channel) send(streamID uint32, t messageType, flags uint8, p []byte) error {
if len(p) > messageLengthMax {
return status.Errorf(codes.ResourceExhausted, "refusing to send, message length %v exceed maximum message size of %v", len(p), messageLengthMax)
return OversizedMessageError(len(p))
}

if err := writeMessageHeader(ch.bw, ch.hwbuf[:], messageHeader{Length: uint32(len(p)), StreamID: streamID, Type: t, Flags: flags}); err != nil {
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48 changes: 47 additions & 1 deletion errors.go
Original file line number Diff line number Diff line change
Expand Up @@ -16,7 +16,12 @@

package ttrpc

import "errors"
import (
"errors"

"google.golang.org/grpc/codes"
"google.golang.org/grpc/status"
)

var (
// ErrProtocol is a general error in the handling the protocol.
Expand All @@ -32,3 +37,44 @@ var (
// ErrStreamClosed is when the streaming connection is closed.
ErrStreamClosed = errors.New("ttrpc: stream closed")
)

// OversizedMessageErr is used to indicate refusal to send an oversized message.
// It wraps a ResourceExhausted grpc Status together with the offending message
// length.
type OversizedMessageErr struct {
messageLength int
err error
}

// OversizedMessageError returns a wrapped ResourceExhausted grpc status code
// together with the offending message length.
func OversizedMessageError(messageLength int) error {
if messageLength <= messageLengthMax {
return nil
}

return &OversizedMessageErr{
messageLength: messageLength,
err: status.Errorf(codes.ResourceExhausted, "message length %v exceed maximum message size of %v", messageLength, messageLengthMax),
}
}

// Error returns the error message for the corresponding grpc Status for the error.
func (e *OversizedMessageErr) Error() string {
return e.err.Error()
}

// GRPCStatus returns the corresponding grpc Status for the error.
func (e *OversizedMessageErr) Unwrap() error {
return e.err
}

// RejectedLength retrieves the rejected message length which triggered the error.
func (e *OversizedMessageErr) RejectedLength() int {
return e.messageLength
}

// MaximumLength retrieves the maximum allowed message length that triggered the error.
func (*OversizedMessageErr) MaximumLength() int {
return messageLengthMax
}

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