void RegionManager::doFlush()

in cachelib/navy/block_cache/RegionManager.cpp [224:278]
41 lines of code
10 McCabe index (conditional complexity)

void RegionManager::doFlush(RegionId rid, bool async) {
  // We're wasting the remaining bytes of a region, so track it for stats
  externalFragmentation_.add(getRegion(rid).getFragmentationSize());

  getRegion(rid).setPendingFlush();
  numInMemBufWaitingFlush_.inc();

  Job flushJob = [this, rid, retryAttempts = 0, flushed = false]() mutable {
    if (!flushed) {
      if (retryAttempts >= inMemBufFlushRetryLimit_) {
        // Flush failure reaches retry limit, stop flushing and start to
        // clean up the buffer.
        if (cleanupBufferOnFlushFailure(rid)) {
          releaseCleanedupRegion(rid);
          return JobExitCode::Done;
        }
        numInMemBufCleanupRetries_.inc();
        return JobExitCode::Reschedule;
      }
      auto res = flushBuffer(rid);
      if (res == Region::FlushRes::kSuccess) {
        flushed = true;
      } else {
        // We have a limited retry limit for flush errors due to device
        if (res == Region::FlushRes::kRetryDeviceFailure) {
          retryAttempts++;
          numInMemBufFlushRetries_.inc();
        }
        return JobExitCode::Reschedule;
      }
    }
    // If the buffer has been successfully flushed or the current flush
    // succeeds, detach the buffer until it succeeds
    if (flushed) {
      if (detachBuffer(rid)) {
        // Flush completed, track the region
        track(rid);
        return JobExitCode::Done;
      }
    }
    return JobExitCode::Reschedule;
  };

  if (async) {
    scheduler_.enqueue(std::move(flushJob), "flush", JobType::Flush);
  } else {
    while (flushJob() == JobExitCode::Reschedule) {
      // We intentionally sleep here to slow it down since this is only
      // triggered on shutdown. On cleanup failures, we will sleep a bit before
      // retrying to avoid maxing out cpu.
      /* sleep override */
      std::this_thread::sleep_for(std::chrono::milliseconds{100});
    }
  }
}