[MESOS-7020] cgroups::internal::write can incorrectly report success

• Type: Bug
• Status: Resolved
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 1.2.0
• Fix Version/s: 1.2.0
• Component/s: containerization

Environment

CentOS7

• Assignee: Jie Yu
• Reporter: Dmitry Zhuk
• Created: 27/Jan/17 16:02
• Updated: 06/Jul/18 21:27
• Resolved: 09/Feb/17 00:20

Description

cgroups::internal::write does not flush stream before checking for errors after writing:

  ofstream file(path.c_str());
...
  file << value;

  if (file.fail()) {
    // TODO(jieyu): Does ofstream actually set errno?
    return ErrnoError();
  }

Since ofstream does internal buffering, file.fail() can return false, as value hasn't been written to file yet.

Replacing file << value; with file << value << std::flush; makes file.fail() behave as expected.