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interceptor.go
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interceptor.go
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/*
* Teleport
* Copyright (C) 2023 Gravitational, Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
package peer
import (
"context"
"sync"
"github.com/gravitational/trace/trail"
"google.golang.org/grpc"
)
// streamWrapper wraps around the embedded grpc.ClientStream
// and intercepts the RecvMsg method calls decreading the number of
// streams counter.
type streamWrapper struct {
grpc.ClientStream
wg *sync.WaitGroup
once sync.Once
}
func (s *streamWrapper) CloseSend() error {
err := s.ClientStream.CloseSend()
s.decreaseCounter()
return err
}
func (s *streamWrapper) SendMsg(m interface{}) error {
err := s.ClientStream.SendMsg(m)
if err != nil {
s.decreaseCounter()
}
return err
}
func (s *streamWrapper) RecvMsg(m interface{}) error {
err := s.ClientStream.RecvMsg(m)
if err != nil {
s.decreaseCounter()
}
return err
}
func (s *streamWrapper) decreaseCounter() {
s.once.Do(func() {
s.wg.Done()
})
}
// streamCounterInterceptor is gRPC client stream interceptor that
// counts the number of current open streams for the purpose of
// gracefully shutdown a draining gRPC client.
func streamCounterInterceptor(wg *sync.WaitGroup) grpc.StreamClientInterceptor {
return func(ctx context.Context, desc *grpc.StreamDesc, cc *grpc.ClientConn, method string, streamer grpc.Streamer, opts ...grpc.CallOption) (grpc.ClientStream, error) {
s, err := streamer(ctx, desc, cc, method, opts...)
if err != nil {
return nil, trail.ToGRPC(err)
}
wg.Add(1)
return &streamWrapper{
ClientStream: s,
wg: wg,
}, nil
}
}