[jira] [Created] (MESOS-10123) Windows overlapped IO discard handling can drop data.

["Benjamin Mahler (Jira)" <ji...@apache.org>]

Benjamin Mahler created MESOS-10123:
---------------------------------------

             Summary: Windows overlapped IO discard handling can drop data.
                 Key: MESOS-10123
                 URL: https://issues.apache.org/jira/browse/MESOS-10123
             Project: Mesos
          Issue Type: Bug
          Components: libprocess
            Reporter: Benjamin Mahler
            Assignee: Benjamin Mahler


When getting a discard request for an io operation on windows, a cancellation is requested [1] and when the io operation completes we check whether the future had a discard request to decide whether to discard it [2]:

{code}
template <typename T>
static void set_io_promise(Promise<T>* promise, const T& data, DWORD error)
{
  if (promise->future().hasDiscard()) {
    promise->discard();
  } else if (error == ERROR_SUCCESS) {
    promise->set(data);
  } else {
    promise->fail("IO failed with error code: " + WindowsError(error).message);
  }
}
{code}

However, it's possible the operation completed successfully, in which case we did not succeed at canceling it. We need to check for {{ERROR_OPERATION_ABORTED}} [3]:

{code}
template <typename T>
static void set_io_promise(Promise<T>* promise, const T& data, DWORD error)
{
  if (promise->future().hasDiscard() && error == ERROR_OPERATION_ABORTED) {
    promise->discard();
  } else if (error == ERROR_SUCCESS) {
    promise->set(data);
  } else {
    promise->fail("IO failed with error code: " + WindowsError(error).message);
  }
}
{code}

I don't think there are currently any major consequences to this issue, since most callers tend to be discarding only when they're essentially abandoning the entire process of reading or writing.

[1] https://github.com/apache/mesos/blob/1.9.0/3rdparty/libprocess/src/windows/libwinio.cpp#L448
[2] https://github.com/apache/mesos/blob/1.9.0/3rdparty/libprocess/src/windows/libwinio.cpp#L141-L151
[3] https://docs.microsoft.com/en-us/windows/win32/fileio/cancelioex-func



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