Delete document with delete signal throw maximum recursion depth exceeded for 0.8.1

[tbicr]

If I subscribe to signals for delete event: I have RuntimeError: maximum recursion depth exceeded, because document delete called again and again: https://github.com/MongoEngine/mongoengine/blob/master/mongoengine/queryset/queryset.py#L430. Affected on 0.8.1, on 0.7.10 all worked right: f182daa.

class Test(Document):
    test = StringField()

def do_nothing(*args, **kwargs):
    pass

post_delete.connect(do_nothing)

Test(test='001').save().delete()

Log example:

  ...
  File "/home/tbicr/Projects/cspw-ui.env/local/lib/python2.7/site-packages/mongoengine/document.py", line 347, in delete
    self._qs.filter(**self._object_key).delete(write_concern=write_concern)
  File "/home/tbicr/Projects/cspw-ui.env/local/lib/python2.7/site-packages/mongoengine/queryset/queryset.py", line 430, in delete
    doc.delete(write_concern=write_concern)
  File "/home/tbicr/Projects/cspw-ui.env/local/lib/python2.7/site-packages/mongoengine/document.py", line 347, in delete
    self._qs.filter(**self._object_key).delete(write_concern=write_concern)
  File "/home/tbicr/Projects/cspw-ui.env/local/lib/python2.7/site-packages/mongoengine/queryset/queryset.py", line 430, in delete
    doc.delete(write_concern=write_concern)
  File "/home/tbicr/Projects/cspw-ui.env/local/lib/python2.7/site-packages/mongoengine/document.py", line 347, in delete
    self._qs.filter(**self._object_key).delete(write_concern=write_concern)
  File "/home/tbicr/Projects/cspw-ui.env/local/lib/python2.7/site-packages/mongoengine/queryset/queryset.py", line 430, in delete
    doc.delete(write_concern=write_concern)
  File "/home/tbicr/Projects/cspw-ui.env/local/lib/python2.7/site-packages/mongoengine/document.py", line 347, in delete
    self._qs.filter(**self._object_key).delete(write_concern=write_concern)
  File "/home/tbicr/Projects/cspw-ui.env/local/lib/python2.7/site-packages/mongoengine/queryset/queryset.py", line 430, in delete
    doc.delete(write_concern=write_concern)
  File "/home/tbicr/Projects/cspw-ui.env/local/lib/python2.7/site-packages/mongoengine/document.py", line 347, in delete
    self._qs.filter(**self._object_key).delete(write_concern=write_concern)
  File "/home/tbicr/Projects/cspw-ui.env/local/lib/python2.7/site-packages/mongoengine/queryset/queryset.py", line 430, in delete
    doc.delete(write_concern=write_concern)
  File "/home/tbicr/Projects/cspw-ui.env/local/lib/python2.7/site-packages/mongoengine/document.py", line 347, in delete
    self._qs.filter(**self._object_key).delete(write_concern=write_concern)
  File "/home/tbicr/Projects/cspw-ui.env/local/lib/python2.7/site-packages/mongoengine/queryset/queryset.py", line 429, in delete
    for doc in queryset:
  File "/home/tbicr/Projects/cspw-ui.env/local/lib/python2.7/site-packages/mongoengine/queryset/queryset.py", line 157, in _iter_results
    self._populate_cache()
  File "/home/tbicr/Projects/cspw-ui.env/local/lib/python2.7/site-packages/mongoengine/queryset/queryset.py", line 167, in _populate_cache
    self._result_cache.append(self.next())
  File "/home/tbicr/Projects/cspw-ui.env/local/lib/python2.7/site-packages/mongoengine/queryset/queryset.py", line 1148, in next
    raw_doc = self._cursor.next()
  File "/home/tbicr/Projects/cspw-ui.env/local/lib/python2.7/site-packages/pymongo/cursor.py", line 814, in next
    if len(self.__data) or self._refresh():
  File "/home/tbicr/Projects/cspw-ui.env/local/lib/python2.7/site-packages/pymongo/cursor.py", line 763, in _refresh
    self.__uuid_subtype))
  File "/home/tbicr/Projects/cspw-ui.env/local/lib/python2.7/site-packages/pymongo/cursor.py", line 700, in __send_message
    **kwargs)
  File "/home/tbicr/Projects/cspw-ui.env/local/lib/python2.7/site-packages/pymongo/mongo_client.py", line 1006, in _send_message_with_response
    self.__pool.maybe_return_socket(sock_info)
  File "/home/tbicr/Projects/cspw-ui.env/local/lib/python2.7/site-packages/pymongo/pool.py", line 358, in maybe_return_socket
    if sock_info != self._get_request_state():
  File "/home/tbicr/Projects/cspw-ui.env/local/lib/python2.7/site-packages/pymongo/pool.py", line 84, in __ne__
    return not self == other
  File "/home/tbicr/Projects/cspw-ui.env/local/lib/python2.7/site-packages/pymongo/pool.py", line 78, in __eq__
    def __eq__(self, other):
  File "/home/tbicr/Soft/pycharm-129.103/helpers/pydev/pydevd.py", line 998, in trace_dispatch
    traceback.print_exc()
  File "/usr/lib/python2.7/traceback.py", line 232, in print_exc
    print_exception(etype, value, tb, limit, file)
  File "/usr/lib/python2.7/traceback.py", line 125, in print_exception
    print_tb(tb, limit, file)
  File "/usr/lib/python2.7/traceback.py", line 67, in print_tb
    '  File "%s", line %d, in %s' % (filename, lineno, name))
RuntimeError: maximum recursion depth exceeded

[rozza]

@tbicr thanks for the ticket will fix in 0.8.2

[rozza]

Your signal is incorrect you should declare a sender alternatively it will be called whenever any post_delete signal is called eg:

post_delete.connect(do_nothing, sender=Test)

I have added a lock in the background as we shouldn't infinite loop if sender isn't given

[tbicr]

Can you clarify next point: as I understand if I have signals and delete documents from queryset then at first I delete documents from document: https://github.com/MongoEngine/mongoengine/blob/master/mongoengine/queryset/queryset.py#L439 (which will call queryset delete) and after with queryset: https://github.com/MongoEngine/mongoengine/blob/master/mongoengine/queryset/queryset.py#L471? So if my conclusion right this code will call delete two times in this case for one document, probably better just send signals before and after remove?

[rozza]

It is convoluted, call_document_delete will be false so it stops signals being called twice.