What causes "failed to configure stdout: %v" in vitessio/vitess?

Raise the file descriptor limit (ulimit -n / systemd LimitNOFILE)

failed to configure stdout: %v

Error message

failed to configure stdout: %v

What it means

ExecuteAsReadPipe sets up the hook process's stdout as a pipe so the caller can read its output. If cmd.StdoutPipe() fails, the function aborts with HOOK_GENERIC_ERROR and this message. Like the stdin variant, it is an OS pipe-creation failure before the process starts.

Source

Thrown at go/vt/hook/hook.go:271

}

// ExecuteAsReadPipe will execute the hook as in a Unix pipe, reading
// from the provided reader. It will return:
// - an io.Reader to read piped data from.
// - a WaitFunc method to call to wait for the process to exit, that
// returns stderr and the Wait() error.
// - an error code and an error if anything fails.
func (hook *Hook) ExecuteAsReadPipe(in io.Reader) (io.Reader, WaitFunc, int, error) {
	// Find the hook.
	cmd, status, err := hook.findHook(context.Background())
	if err != nil {
		return nil, nil, status, err
	}

	// Configure the process's stdin, stdout, and stderr.
	out, err := cmd.StdoutPipe()
	if err != nil {
		return nil, nil, HOOK_GENERIC_ERROR, fmt.Errorf("failed to configure stdout: %v", err)
	}
	cmd.Stdin = in
	var stderr strings.Builder
	cmd.Stderr = &stderr

	// Start the process.
	err = cmd.Start()
	if err != nil {
		status = HOOK_CANNOT_GET_EXIT_STATUS
		if cmd.ProcessState != nil {
			status = cmd.ProcessState.Sys().(syscall.WaitStatus).ExitStatus()
		}
		return nil, nil, status, err
	}

	// And return
	return out, func() (string, error) {
		err := cmd.Wait()

View on GitHub (pinned to 01a25a7d17)

Solutions

Raise the file descriptor limit (ulimit -n / systemd LimitNOFILE)
Find and fix file-descriptor leaks (unclosed pipes/connections) in the calling process
Check the wrapped %v OS error from StdoutPipe for the precise cause

Example fix

// before: 'failed to configure stdout: too many open files'
// after (docker)
docker run --ulimit nofile=65536:65536 ...

Defensive patterns

Strategy: fallback

Validate before calling

if err := isFDHeadroomOK(4); err != nil {
    return fmt.Errorf("not enough file descriptors for hook pipe: %v", err)
}

Try / catch

r, hr, status, err := h.ExecuteAsReadPipe(ctx, nil)
if status == hook.HOOK_GENERIC_ERROR && strings.Contains(err.Error(), "failed to configure stdout") {
    return fmt.Errorf("pipe setup failed (check ulimit -n): %v", err)
}

Prevention

Set nofile ulimits generously in containers and systemd units
Drain and close stdout pipes (read to EOF) to avoid leaks
Reuse hook execution paths that guarantee pipe cleanup via defer

When it happens

Trigger: Calling hook.ExecuteAsReadPipe when the exec.Cmd StdoutPipe call fails — typically OS file-descriptor exhaustion or invalid cmd state.

Common situations: FD exhaustion from leaked pipes in long-running processes; containers with low nofile limits; reusing an exec.Cmd whose pipes were already configured.

Related errors

AI-assisted analysis of vitessio/vitess@01a25a7d17 (2026-09-01). Data as JSON: /api/errors/3d62f0faf2c1fec0. Report an issue: GitHub.