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server: wait to close connection until incoming socket is drained (with timeout) #6977

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merged 2 commits into from Feb 12, 2024
Merged

server: wait to close connection until incoming socket is drained (with timeout) #6977

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f416f95
server: wait to close connection until incoming socket is drained (wi…
dfawley Feb 9, 2024
ff4b564
don't close for i/o errors to match prior behavior
dfawley Feb 9, 2024
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5 changes: 2 additions & 3 deletions internal/transport/controlbuf.go
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Expand Up @@ -535,16 +535,15 @@ const minBatchSize = 1000
// size is too low to give stream goroutines a chance to fill it up.
//
// Upon exiting, if the error causing the exit is not an I/O error, run()
// flushes and closes the underlying connection. Otherwise, the connection is
// left open to allow the I/O error to be encountered by the reader instead.
// flushes the underlying connection. The connection is always left open to
// allow different closing behavior on the client and server.
func (l *loopyWriter) run() (err error) {
defer func() {
if l.logger.V(logLevel) {
l.logger.Infof("loopyWriter exiting with error: %v", err)
}
if !isIOError(err) {
l.framer.writer.Flush()
l.conn.Close()
}
l.cbuf.finish()
}()
Expand Down
8 changes: 7 additions & 1 deletion internal/transport/http2_client.go
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Expand Up @@ -451,7 +451,13 @@ func newHTTP2Client(connectCtx, ctx context.Context, addr resolver.Address, opts
}
go func() {
t.loopy = newLoopyWriter(clientSide, t.framer, t.controlBuf, t.bdpEst, t.conn, t.logger)
t.loopy.run()
if err := t.loopy.run(); !isIOError(err) {
// Immediately close the connection, as the loopy writer returns
// when there are no more active streams and we were draining (the
// server sent a GOAWAY). For I/O errors, the reader will hit it
// after draining any remaining incoming data.
t.conn.Close()
}
close(t.writerDone)
}()
return t, nil
Expand Down
23 changes: 20 additions & 3 deletions internal/transport/http2_server.go
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Expand Up @@ -322,8 +322,24 @@ func NewServerTransport(conn net.Conn, config *ServerConfig) (_ ServerTransport,
go func() {
t.loopy = newLoopyWriter(serverSide, t.framer, t.controlBuf, t.bdpEst, t.conn, t.logger)
t.loopy.ssGoAwayHandler = t.outgoingGoAwayHandler
t.loopy.run()
err := t.loopy.run()
close(t.loopyWriterDone)
if !isIOError(err) {
// Close the connection if a non-I/O error occurs (for I/O errors
// the reader will also encounter the error and close). Wait 1
// second before closing the connection, or when the reader is done
// (i.e. the client already closed the connection or a connection
// error occurred). This avoids the potential problem where there
// is unread data on the receive side of the connection, which, if
// closed, would lead to a TCP RST instead of FIN, and the client
// encountering errors. For more info:
// https://github.com/grpc/grpc-go/issues/5358
select {
case <-t.readerDone:
case <-time.After(time.Second):
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@mtekeli mtekeli Feb 14, 2024 •
edited

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Note that no one can stop this scheduled timer when the reader is done first (which would probably happen most of the times). I would suggest to change it to a timer object so it can be stopped manually (and therefore released) when the reader is done first.

In a scenario where this happens with many clients (or the same client) repeatedly wouldn't you just schedule many timers that cannot be stopped until they fire (i.e a temporary memory leak)?

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True that it isn't stopped, but it is fixed for 1 second, so I don't believe this could be a real problem for anyone.

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Even when many connections having non IO errors? Do you think it's unlikely or even not possible?

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I think the key here is that it's a non-I/O error, which means it would be initiated by the server itself. If the server is terminating already-handshaked connections at a rate of >1 per second, then that seems like a real problem.

That said, I think it's OK to just forbid the use of time.After in our repo (outside of tests) since it's always a potential concern. I'll add a vet.sh check for this and change it on master.

}
t.conn.Close()
}
}()
go t.keepalive()
return t, nil
Expand Down Expand Up @@ -609,8 +625,8 @@ func (t *http2Server) operateHeaders(ctx context.Context, frame *http2.MetaHeade
// traceCtx attaches trace to ctx and returns the new context.
func (t *http2Server) HandleStreams(ctx context.Context, handle func(*Stream)) {
defer func() {
<-t.loopyWriterDone
close(t.readerDone)
<-t.loopyWriterDone
}()
for {
t.controlBuf.throttle()
Expand Down Expand Up @@ -1325,6 +1341,7 @@ func (t *http2Server) outgoingGoAwayHandler(g *goAway) (bool, error) {
if err := t.framer.fr.WriteGoAway(sid, g.code, g.debugData); err != nil {
return false, err
}
t.framer.writer.Flush()
if retErr != nil {
return false, retErr
}
Expand All @@ -1345,7 +1362,7 @@ func (t *http2Server) outgoingGoAwayHandler(g *goAway) (bool, error) {
return false, err
}
go func() {
timer := time.NewTimer(time.Minute)
timer := time.NewTimer(5 * time.Second)
defer timer.Stop()
select {
case <-t.drainEvent.Done():
Expand Down