Function test_flush_max_us_impl

lib/cpp/test/TFileTransportTest.cpp:224–289

* Make sure setFlushMaxUs() is honored. */

 * Make sure setFlushMaxUs() is honored.
 */
void test_flush_max_us_impl(uint32_t flush_us, uint32_t write_us, uint32_t test_us) {
  // TFileTransport only calls fsync() if data has been written,
  // so make sure the write interval is smaller than the flush interval.
  BOOST_WARN(write_us < flush_us);

  TempFile f(tmp_dir, "thrift.TFileTransportTest.");

  // Record calls to fsync()
  FsyncLog log;
  fsync_log = &log;

  TFileTransport* transport = new TFileTransport(f.getPath());
  // Don't flush because of # of bytes written
  transport->setFlushMaxBytes(0xffffffff);
  uint8_t buf[] = "a";
  uint32_t buflen = sizeof(buf);

  // Set the flush interval
  transport->setFlushMaxUs(flush_us);

  // Make one call to write, to start the writer thread now.
  // (If we just let the thread get created during our test loop,
  // the thread creation sometimes takes long enough to make the first
  // fsync interval fail the check.)
  transport->write(buf, buflen);

  // Add one entry to the fsync log, just to mark the start time
  log.fsync(-1);

  // Loop doing write(), sleep(), ...
  uint32_t total_time = 0;
  while (true) {
    transport->write(buf, buflen);
    if (total_time > test_us) {
      break;
    }
    usleep(write_us);
    total_time += write_us;
  }

  delete transport;

  // Stop logging new fsync() calls
  fsync_log = nullptr;

  // Examine the fsync() log
  //
  // TFileTransport uses pthread_cond_timedwait(), which only has millisecond
  // resolution.  In my testing, it normally wakes up about 1 millisecond late.
  // However, sometimes it takes a bit longer.  Allow 5ms leeway.
  int max_allowed_delta = flush_us + 5000;

  const FsyncLog::CallList* calls = log.getCalls();
  // We added 1 fsync call above.
  // Make sure TFileTransport called fsync at least once
  BOOST_WARN_GE(calls->size(), static_cast<FsyncLog::CallList::size_type>(1));

  const struct timeval* prev_time = nullptr;