Problems monitoring a file for metadata changes

I need to monitor a file for when its metadata changes.

I'm using the following code I found.

Code Block 
final class FileMonitor
{
  let url: URL
  var fileHandle: FileHandle?
  var source: DispatchSourceFileSystemObject?
  var didReceiveChanges: (() -> Void)?
  func process(event: DispatchSource.FileSystemEvent)
  {
    print(String(describing: event))
    didReceiveChanges?()
  }
  func eventHandler()
  {
    let event = self.source!.data
    process(event: event)
    createDispatchSource()
  }
  func createDispatchSource()
  {
    self.fileHandle = try? FileHandle(forReadingFrom: url)
    source = DispatchSource.makeFileSystemObjectSource(fileDescriptor: fileHandle!.fileDescriptor, eventMask: [.attrib], queue: DispatchQueue.main)
    source!.setEventHandler(handler: eventHandler)
    source!.setCancelHandler
    {
      self.fileHandle!.closeFile()
    }
    source!.resume()
  }
  init(url: URL) throws
  {
    self.url = url
    createDispatchSource()
  }
  deinit
  {
    source!.cancel()
  }
}

The problem is that I am getting nearly 7,000 notifications every time a change is detected, which is causing the CPU to get rather warm.

This subject seems to be very poorly documented and after days searching, I don't seem to be able to make things any better.

Any ideas please?

Joanna