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Don't cancel run context on stdin EOF #296

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llogen wants to merge 1 commit into from
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Don't cancel run context on stdin EOF #296

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12 changes: 7 additions & 5 deletions cmds/dutctl/rpc.go
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Original file line number Diff line number Diff line change
Expand Up @@ -100,6 +100,7 @@ func (app *application) runRPC(device, command string, cmdArgs []string) error {
defer cancel()

errChan := make(chan error, numWorkers)
recvDone := make(chan struct{})

stream := app.rpcClient.Run(runCtx)
req := &pb.RunRequest{
Expand Down Expand Up @@ -127,6 +128,7 @@ func (app *application) runRPC(device, command string, cmdArgs []string) error {

// Receive routine
go func() {
defer close(recvDone)
defer cancel()

for {
Expand Down Expand Up @@ -226,10 +228,9 @@ func (app *application) runRPC(device, command string, cmdArgs []string) error {
}
}()

// Send routine
// Send routine — stdin EOF must not cancel the context; only the receive
// routine drives termination so that all server responses are processed.
go func() {
defer cancel()

reader := bufio.NewReader(app.stdin)

for {
Comment on lines +231 to 236
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Copilot AI Mar 12, 2026

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Now that stdin EOF no longer cancels the context (good), the send routine still exits on io.EOF without half-closing the client->server request stream. Server-side code treats client stream closure (io.EOF on Receive) as the signal that no more requests are coming; consider explicitly closing the request side (e.g., stream.CloseRequest()/equivalent for connect.BidiStreamForClient) when stdin reaches EOF so the server can stop waiting for further client messages without relying on full context cancellation.

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Expand Down Expand Up @@ -267,9 +268,10 @@ func (app *application) runRPC(device, command string, cmdArgs []string) error {
}
}()

// Wait for completion or error
// Wait for the receive routine to finish (stream closed or cancelled) or for
// any worker to report an error.
select {
case <-runCtx.Done():
case <-recvDone:
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Copilot AI Mar 12, 2026

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recvDone is closed unconditionally in the receive goroutine, including when that goroutine hits a non-EOF error and sends it on errChan. In that situation both recvDone and errChan can become ready, and the final select may pick recvDone and return nil, silently dropping the receive error (same for a send error racing with receive completion). Consider making the completion signal carry an error (e.g., recvDone chan error) or, at minimum, ensure the recvDone path checks/drains errChan before returning nil so real worker errors can’t be lost.

Suggested change
case <-recvDone:
case <-recvDone:
// Prefer any pending worker error over a silent success.
select {
case err := <-errChan:
if err != nil {
return err
}
default:
}

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return nil
case err := <-errChan:
return err
Expand Down
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