func startBackground()

in integration/utils/exec.go [139:177]

• 28 lines of code
• 5 McCabe index (conditional complexity)

func startBackground(cookie string, stdout io.Writer, stderr io.Writer, user *UnixUser, args ...string) (*exec.Cmd, io.WriteCloser, error) {
	bin := GetConfig().SandboxfsBinary

	// The sandboxfs command line syntax requires the mount point to appear at the end and we
	// control all callers of this function within the tests, so we know this is true.  If not,
	// well, we have a bug and the test will crash/fail.
	mountPoint := args[len(args)-1]

	cmd := exec.Command(bin, args...)
	stdin, err := cmd.StdinPipe()
	if err != nil {
		return nil, nil, fmt.Errorf("failed to create stdin pipe: %v", err)
	}
	cmd.Stdout = stdout
	cmd.Stderr = stderr
	SetCredential(cmd, user)
	setRustEnv(cmd)
	if err := cmd.Start(); err != nil {
		return nil, nil, fmt.Errorf("failed to start %s with arguments %v: %v", bin, args, err)
	}

	if cookie != "" {
		cookiePath := filepath.Join(mountPoint, cookie)
		waitForCookie := func() error { return FileExistsAsUser(cookiePath, user) }
		if err := retry(waitForCookie, "waiting for cookie to appear in mount point", startupDeadlineSeconds); err != nil {
			// Give up.  sandboxfs did't come up, so kill the process and clean up.
			// There is not much we can do here if we encounter errors (e.g. we don't
			// even know if the mount point was initialized, so the unmount call may or
			// may not fail) so just try to clean up as much as possible.
			stdin.Close()
			cmd.Process.Kill()
			cmd.Wait()
			Unmount(mountPoint)
			return nil, nil, fmt.Errorf("file system failed to come up: %s not found", cookiePath)
		}
	}

	return cmd, stdin, nil
}