mod_wsgi: failing isinstance checks on mod_wsgi 4.5.3/Apache 2.4/Windows

Fair warning - we’ve been hitting the wall on this issue for a couple of months now and trying to pin the problem.

Technical stack

  • Windows Server
  • Apache 2.4
  • Python 2.7.12 64 bit (msi installer)
  • mod_wsgi-py27-VC9.so, version 4.5.3
  • Django 1.9
  • third party packages installed:
    #
# This file is autogenerated by pip-compile
# To update, run:
#
#    pip-compile --output-file requirements/base.txt requirements/base.in
#
-e git+https://redacted/pdf2xml_project.git@1.7.7#egg=pdf2xml
abbyy==0.3
amqp==2.1.4               # via kombu
backports.functools-lru-cache==1.3
billiard==3.5.0.2         # via celery
celery==4.0.2
chardet==3.0.2            # via pdfquery
click==6.7                # via pip-tools, python-dotenv
contextlib2==0.5.4        # via raven
cssselect==1.0.1          # via pdfquery, pyquery
diff-match-patch==20121119  # via django-import-export
django-choices==1.4.4
django-extra-fields==0.8.0
django-extra-views==0.8.0
django-import-export==0.5.0
django-redis==4.7.0
django-sniplates==0.5.0
django==1.10.7
djangorestframework==3.3.3
first==2.0.1              # via pip-tools
kombu==4.0.2              # via celery
langdetect==1.0.6
lxml==3.7.3               # via abbyy, pdfquery, pyquery
pdfminer==20140328
pdfquery==0.4.3
pillow==3.4.2
pip-tools==1.9.0
psycopg2==2.6.2
pypdf2==1.26.0
pyquery==1.2.17           # via pdfquery
python-dotenv==0.6.1
python-levenshtein==0.12.0
pytz==2017.2              # via celery
qrcode==5.3
raven==5.32.0
redis==2.10.5
requests==2.13.0          # via abbyy
roman==2.0.0              # via pdfquery
six==1.10.0               # via django-choices, django-extra-views, langdetect, pdfquery, pip-tools, qrcode
tablib==0.11.4
unipath==1.1
vine==1.1.3               # via amqp

Linux

The same app (same versions of python libs and app) is also deployed on Linux boxes, were we haven’t observed this problem.

Problem description

We’re making use of django’s UUIDField, which does typecasting to handle strings/uuid.UUID objects and send the right type to the database driver depending on if the backend has native support for uuid or not.

We’ve been hitting odd AttributeErrors on Django’s attempt to cast after a ‘lying’ isinstance check.

The relevant Django code is (in django.db.fields.UUIDField):

def get_db_prep_value(self, value, connection, prepared=False):
    if value is None:
        return None
    if not isinstance(value, uuid.UUID):
        try:
            value = uuid.UUID(value)
        except AttributeError:
            raise TypeError(self.error_messages['invalid'] % {'value': value})

    if connection.features.has_native_uuid_field:
        return value
    return value.hex

The actual AttributeError is masked and re-raised as a TypeError.

Preliminary investigation showed us that value is actual an uuid.UUID instance.

Analysis + Logging we added

We’ve added a lot of logging to this method to be able to figure out the problem. The result is that the method now looks like this:

def get_db_prep_value(self, value, connection, prepared=False):
    import logging
    import inspect
    logger = logging.getLogger('smartscan')
    if value is None:
        return None
    logger.warning('Value id before isinstance check: %s', id(value))
    if not isinstance(value, uuid.UUID):
        logger.warning('Actual type: %s', type(value))
        logger.warning('Is isinstance lying? %s', type(value) == uuid.UUID)
        logger.warning('uuid module used: %s', value.__class__.__module__)
        if value.__class__ is not unicode:
            logger.warning('id(uuid): %s', id(uuid))
            logger.warning('id(uuid.UUID): %s', id(uuid.UUID))
            logger.warning('id(type(value)): %s', id(type(value)))
            logger.warning('module file of `value` class: %s', inspect.getfile(value.__class__))
            sanity_check = uuid.uuid4()
            logger.warning('Functional isinstance? %s', isinstance(sanity_check, uuid.UUID) is True)
            logger.warning('Functional isinstance2? %s', isinstance(u'foo', unicode) is True)
        logger.warning(
            'Failed isinstance check, uuid module: %s',
            uuid.__file__
        )
        logger.warning('Value id after isinstance check: %s', id(value))
        try:
            logger.warning('Value id before cast: %s', id(value))
            value = uuid.UUID(value)
            logger.warning('Value id after cast: %s', id(value))
        except AttributeError:
            logger.exception('Failed cast: value type and id: %s, %s', type(value), id(value))
            raise TypeError(self.error_messages['invalid'] % {'value': value})

    if connection.features.has_native_uuid_field:
        return value
    return value.hex

with sample logging output:

WARNING May, 17 2017 13:43:30 smartscan            2356 948 Value id before isinstance check: 152464528
WARNING May, 17 2017 13:43:30 smartscan            2356 948 Actual type: <type 'unicode'>
WARNING May, 17 2017 13:43:30 smartscan            2356 948 Is isinstance lying? False
WARNING May, 17 2017 13:43:30 smartscan            2356 948 uuid module used: __builtin__
WARNING May, 17 2017 13:43:30 smartscan            2356 948 Failed isinstance check, uuid module: C:\IBM\python27\Lib\uuid.pyc
WARNING May, 17 2017 13:43:30 smartscan            2356 948 Value id after isinstance check: 152464528
WARNING May, 17 2017 13:43:30 smartscan            2356 948 Value id before cast: 152464528
WARNING May, 17 2017 13:43:30 smartscan            2356 948 Value id after cast: 120038792
WARNING May, 17 2017 13:43:30 smartscan            2356 948 Value id before isinstance check: 152464528
WARNING May, 17 2017 13:43:30 smartscan            2356 948 Actual type: <type 'unicode'>
WARNING May, 17 2017 13:43:30 smartscan            2356 948 Is isinstance lying? False
WARNING May, 17 2017 13:43:30 smartscan            2356 948 uuid module used: __builtin__
WARNING May, 17 2017 13:43:30 smartscan            2356 948 Failed isinstance check, uuid module: C:\IBM\python27\Lib\uuid.pyc
WARNING May, 17 2017 13:43:30 smartscan            2356 948 Value id after isinstance check: 152464528
WARNING May, 17 2017 13:43:30 smartscan            2356 948 Value id before cast: 152464528
WARNING May, 17 2017 13:43:30 smartscan            2356 948 Value id after cast: 120038904
WARNING May, 17 2017 13:43:30 smartscan            2356 948 Value id before isinstance check: 152464528
WARNING May, 17 2017 13:43:30 smartscan            2356 948 Actual type: <type 'unicode'>
WARNING May, 17 2017 13:43:30 smartscan            2356 948 Is isinstance lying? False
WARNING May, 17 2017 13:43:30 smartscan            2356 948 uuid module used: __builtin__
WARNING May, 17 2017 13:43:30 smartscan            2356 948 Failed isinstance check, uuid module: C:\IBM\python27\Lib\uuid.pyc
WARNING May, 17 2017 13:43:30 smartscan            2356 948 Value id after isinstance check: 152464528
WARNING May, 17 2017 13:43:30 smartscan            2356 948 Value id before cast: 152464528
WARNING May, 17 2017 13:43:30 smartscan            2356 948 Value id after cast: 970260040
WARNING May, 17 2017 13:43:30 smartscan            2356 948 Value id before isinstance check: 152464528
WARNING May, 17 2017 13:43:30 smartscan            2356 948 Actual type: <type 'unicode'>
WARNING May, 17 2017 13:43:30 smartscan            2356 948 Is isinstance lying? False
WARNING May, 17 2017 13:43:30 smartscan            2356 948 uuid module used: __builtin__
WARNING May, 17 2017 13:43:30 smartscan            2356 948 Failed isinstance check, uuid module: C:\IBM\python27\Lib\uuid.pyc
WARNING May, 17 2017 13:43:30 smartscan            2356 948 Value id after isinstance check: 152464528
WARNING May, 17 2017 13:43:30 smartscan            2356 948 Value id before cast: 152464528
WARNING May, 17 2017 13:43:30 smartscan            2356 948 Value id after cast: 416975280
INFO May, 17 2017 13:43:30 smartscan.pdf2xmlapp.pdf_handler 2356 948 Received PDF for decoding ...
INFO May, 17 2017 13:43:30 smartscan.pdf2xmlapp.pdf_handler 2356 948 Start pre-parsing with template 1
INFO May, 17 2017 13:43:30 smartscan.pdf2xmlapp.utils 2356 948 Found a fuzzy ('0025_602988') via unique_identifier 'NAR'
INFO May, 17 2017 13:43:30 smartscan.pdf2xmlapp.utils 2356 948 Found exactly 1 template: '0025_602988_en'.
INFO May, 17 2017 13:43:30 smartscan.pdf2xmlapp.pdf_handler 2356 948 Start full parsing PDF with template 43
INFO May, 17 2017 13:43:31 smartscan.pdf2xmlapp.pdf_handler 2356 948 Done full parsing PDF with template 43
WARNING May, 17 2017 13:43:31 smartscan            2356 948 Value id before isinstance check: 152464528
WARNING May, 17 2017 13:43:31 smartscan            2356 948 Actual type: <type 'unicode'>
WARNING May, 17 2017 13:43:31 smartscan            2356 948 Is isinstance lying? False
WARNING May, 17 2017 13:43:31 smartscan            2356 948 uuid module used: __builtin__
WARNING May, 17 2017 13:43:31 smartscan            2356 948 Failed isinstance check, uuid module: C:\IBM\python27\Lib\uuid.pyc
WARNING May, 17 2017 13:43:31 smartscan            2356 948 Value id after isinstance check: 152464528
WARNING May, 17 2017 13:43:31 smartscan            2356 948 Value id before cast: 152464528
WARNING May, 17 2017 13:43:31 smartscan            2356 948 Value id after cast: 391117624
WARNING May, 17 2017 13:43:31 smartscan            2356 948 Value id before isinstance check: 148428392
WARNING May, 17 2017 13:43:31 smartscan            2356 948 Actual type: <class 'uuid.UUID'>
WARNING May, 17 2017 13:43:31 smartscan            2356 948 Is isinstance lying? False
WARNING May, 17 2017 13:43:31 smartscan            2356 948 uuid module used: uuid
WARNING May, 17 2017 13:43:31 smartscan            2356 948 id(uuid): 43429848
WARNING May, 17 2017 13:43:31 smartscan            2356 948 id(uuid.UUID): 41308792
WARNING May, 17 2017 13:43:31 smartscan            2356 948 id(type(value)): 416421896
WARNING May, 17 2017 13:43:31 smartscan            2356 948 module file of `value` class: C:\IBM\python27\Lib\uuid.pyc
WARNING May, 17 2017 13:43:31 smartscan            2356 948 Functional isinstance? True
WARNING May, 17 2017 13:43:31 smartscan            2356 948 Functional isinstance2? True
WARNING May, 17 2017 13:43:31 smartscan            2356 948 Failed isinstance check, uuid module: C:\IBM\python27\Lib\uuid.pyc
WARNING May, 17 2017 13:43:31 smartscan            2356 948 Value id after isinstance check: 148428392
WARNING May, 17 2017 13:43:31 smartscan            2356 948 Value id before cast: 148428392
ERROR May, 17 2017 13:43:31 smartscan            2356 948 Failed cast: value type and id: <class 'uuid.UUID'>, 148428392
Traceback (most recent call last):
  File "D:\redacted\backend\env\lib\site-packages\django\db\models\fields\__init__.py", line 2425, in get_db_prep_value
    value = uuid.UUID(value)
  File "C:\IBM\python27\Lib\uuid.py", line 133, in __init__
    hex = hex.replace('urn:', '').replace('uuid:', '')
AttributeError: 'UUID' object has no attribute 'replace'
WARNING May, 17 2017 13:43:32 smartscan            2356 948 Value id before isinstance check: 148428392
WARNING May, 17 2017 13:43:32 smartscan            2356 948 Actual type: <class 'uuid.UUID'>
WARNING May, 17 2017 13:43:32 smartscan            2356 948 Is isinstance lying? False
WARNING May, 17 2017 13:43:32 smartscan            2356 948 uuid module used: uuid
WARNING May, 17 2017 13:43:32 smartscan            2356 948 id(uuid): 43429848
WARNING May, 17 2017 13:43:32 smartscan            2356 948 id(uuid.UUID): 41308792
WARNING May, 17 2017 13:43:32 smartscan            2356 948 id(type(value)): 416421896
WARNING May, 17 2017 13:43:32 smartscan            2356 948 module file of `value` class: C:\IBM\python27\Lib\uuid.pyc
WARNING May, 17 2017 13:43:32 smartscan            2356 948 Functional isinstance? True
WARNING May, 17 2017 13:43:32 smartscan            2356 948 Functional isinstance2? True
WARNING May, 17 2017 13:43:32 smartscan            2356 948 Failed isinstance check, uuid module: C:\IBM\python27\Lib\uuid.pyc
WARNING May, 17 2017 13:43:32 smartscan            2356 948 Value id after isinstance check: 148428392
WARNING May, 17 2017 13:43:32 smartscan            2356 948 Value id before cast: 148428392
ERROR May, 17 2017 13:43:32 smartscan            2356 948 Failed cast: value type and id: <class 'uuid.UUID'>, 148428392
Traceback (most recent call last):
  File "D:\redacted\backend\env\lib\site-packages\django\db\models\fields\__init__.py", line 2425, in get_db_prep_value
    value = uuid.UUID(value)
  File "C:\IBM\python27\Lib\uuid.py", line 133, in __init__
    hex = hex.replace('urn:', '').replace('uuid:', '')
AttributeError: 'UUID' object has no attribute 'replace'
WARNING May, 17 2017 13:43:32 smartscan            2356 948 Value id before isinstance check: 148428392
WARNING May, 17 2017 13:43:32 smartscan            2356 948 Actual type: <class 'uuid.UUID'>
WARNING May, 17 2017 13:43:32 smartscan            2356 948 Is isinstance lying? False
WARNING May, 17 2017 13:43:32 smartscan            2356 948 uuid module used: uuid
WARNING May, 17 2017 13:43:32 smartscan            2356 948 id(uuid): 43429848
WARNING May, 17 2017 13:43:32 smartscan            2356 948 id(uuid.UUID): 41308792
WARNING May, 17 2017 13:43:32 smartscan            2356 948 id(type(value)): 416421896
WARNING May, 17 2017 13:43:32 smartscan            2356 948 module file of `value` class: C:\IBM\python27\Lib\uuid.pyc
WARNING May, 17 2017 13:43:32 smartscan            2356 948 Functional isinstance? True
WARNING May, 17 2017 13:43:32 smartscan            2356 948 Functional isinstance2? True
WARNING May, 17 2017 13:43:32 smartscan            2356 948 Failed isinstance check, uuid module: C:\IBM\python27\Lib\uuid.pyc
WARNING May, 17 2017 13:43:32 smartscan            2356 948 Value id after isinstance check: 148428392
WARNING May, 17 2017 13:43:32 smartscan            2356 948 Value id before cast: 148428392
ERROR May, 17 2017 13:43:32 smartscan            2356 948 Failed cast: value type and id: <class 'uuid.UUID'>, 148428392
Traceback (most recent call last):
  File "D:\redacted\backend\env\lib\site-packages\django\db\models\fields\__init__.py", line 2425, in get_db_prep_value
    value = uuid.UUID(value)
  File "C:\IBM\python27\Lib\uuid.py", line 133, in __init__
    hex = hex.replace('urn:', '').replace('uuid:', '')
AttributeError: 'UUID' object has no attribute 'replace'
ERROR May, 17 2017 13:43:31 django.request       2356 948 Internal Server Error: /smartscan/viewer/side-by-side/template/43/
Traceback (most recent call last):
  File "D:\redacted\backend\env\lib\site-packages\django\core\handlers\base.py", line 149, in get_response
    response = self.process_exception_by_middleware(e, request)
  File "D:\redacted\backend\env\lib\site-packages\django\core\handlers\base.py", line 147, in get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "D:\redacted\backend\env\lib\site-packages\django\views\generic\base.py", line 68, in view
    return self.dispatch(request, *args, **kwargs)
  File "D:\redacted\smartscan\backend\src\smartscan\viewer\views.py", line 263, in dispatch
    return super(SideBySideView, self).dispatch(request, *args, **kwargs)
  File "D:\redacted\backend\env\lib\site-packages\django\contrib\auth\mixins.py", line 56, in dispatch
    return super(LoginRequiredMixin, self).dispatch(request, *args, **kwargs)
  File "D:\redacted\backend\env\lib\site-packages\django\views\generic\base.py", line 88, in dispatch
    return handler(request, *args, **kwargs)
  File "D:\redacted\backend\env\lib\site-packages\django\views\generic\edit.py", line 279, in post
    return super(BaseUpdateView, self).post(request, *args, **kwargs)
  File "D:\redacted\backend\env\lib\site-packages\django\views\generic\edit.py", line 222, in post
    return self.form_valid(form)
  File "D:\redacted\smartscan\backend\src\smartscan\viewer\views.py", line 401, in form_valid
    return HttpResponseRedirect(self.get_success_url())
  File "D:\redacted\smartscan\backend\src\smartscan\viewer\views.py", line 368, in get_success_url
    self.set_invoice_data(invoice_data)
  File "D:\redacted\smartscan\backend\src\smartscan\viewer\views.py", line 337, in set_invoice_data
    invoice_data.save()
  File "D:\redacted\backend\env\lib\site-packages\django\db\models\base.py", line 708, in save
    force_update=force_update, update_fields=update_fields)
  File "D:\redacted\backend\env\lib\site-packages\django\db\models\base.py", line 736, in save_base
    updated = self._save_table(raw, cls, force_insert, force_update, using, update_fields)
  File "D:\redacted\backend\env\lib\site-packages\django\db\models\base.py", line 801, in _save_table
    forced_update)
  File "D:\redacted\backend\env\lib\site-packages\django\db\models\base.py", line 851, in _do_update
    return filtered._update(values) > 0
  File "D:\redacted\backend\env\lib\site-packages\django\db\models\query.py", line 645, in _update
    return query.get_compiler(self.db).execute_sql(CURSOR)
  File "D:\redacted\backend\env\lib\site-packages\django\db\models\sql\compiler.py", line 1149, in execute_sql
    cursor = super(SQLUpdateCompiler, self).execute_sql(result_type)
  File "D:\redacted\backend\env\lib\site-packages\django\db\models\sql\compiler.py", line 837, in execute_sql
    sql, params = self.as_sql()
  File "D:\redacted\backend\env\lib\site-packages\django\db\models\sql\compiler.py", line 1137, in as_sql
    where, params = self.compile(self.query.where)
  File "D:\redacted\backend\env\lib\site-packages\django\db\models\sql\compiler.py", line 366, in compile
    sql, params = node.as_sql(self, self.connection)
  File "D:\redacted\backend\env\lib\site-packages\django\db\models\sql\where.py", line 79, in as_sql
    sql, params = compiler.compile(child)
  File "D:\redacted\backend\env\lib\site-packages\django\db\models\sql\compiler.py", line 366, in compile
    sql, params = node.as_sql(self, self.connection)
  File "D:\redacted\backend\env\lib\site-packages\django\db\models\lookups.py", line 158, in as_sql
    rhs_sql, rhs_params = self.process_rhs(compiler, connection)
  File "D:\redacted\backend\env\lib\site-packages\django\db\models\lookups.py", line 91, in process_rhs
    return self.get_db_prep_lookup(value, connection)
  File "D:\redacted\backend\env\lib\site-packages\django\db\models\lookups.py", line 62, in get_db_prep_lookup
    self.lookup_name, value, connection, prepared=True))
  File "D:\redacted\backend\env\lib\site-packages\django\db\models\fields\__init__.py", line 776, in get_db_prep_lookup
    prepared=prepared)]
  File "D:\redacted\backend\env\lib\site-packages\django\db\models\fields\__init__.py", line 2429, in get_db_prep_value
    raise TypeError(self.error_messages['invalid'] % {'value': value})
TypeError: '47ff7acf-eefa-4a86-8fa2-1609fdfe8278' is not a valid UUID.
WARNING May, 17 2017 13:43:33 smartscan            2356 948 Value id before isinstance check: 148428392
WARNING May, 17 2017 13:43:33 smartscan            2356 948 Actual type: <class 'uuid.UUID'>
WARNING May, 17 2017 13:43:33 smartscan            2356 948 Is isinstance lying? False
WARNING May, 17 2017 13:43:33 smartscan            2356 948 uuid module used: uuid
WARNING May, 17 2017 13:43:33 smartscan            2356 948 id(uuid): 43429848
WARNING May, 17 2017 13:43:33 smartscan            2356 948 id(uuid.UUID): 41308792
WARNING May, 17 2017 13:43:33 smartscan            2356 948 id(type(value)): 416421896
WARNING May, 17 2017 13:43:33 smartscan            2356 948 module file of `value` class: C:\IBM\python27\Lib\uuid.pyc
WARNING May, 17 2017 13:43:33 smartscan            2356 948 Functional isinstance? True
WARNING May, 17 2017 13:43:33 smartscan            2356 948 Functional isinstance2? True
WARNING May, 17 2017 13:43:33 smartscan            2356 948 Failed isinstance check, uuid module: C:\IBM\python27\Lib\uuid.pyc
WARNING May, 17 2017 13:43:33 smartscan            2356 948 Value id after isinstance check: 148428392
WARNING May, 17 2017 13:43:33 smartscan            2356 948 Value id before cast: 148428392
ERROR May, 17 2017 13:43:33 smartscan            2356 948 Failed cast: value type and id: <class 'uuid.UUID'>, 148428392
Traceback (most recent call last):
  File "D:\redacted\backend\env\lib\site-packages\django\db\models\fields\__init__.py", line 2425, in get_db_prep_value
    value = uuid.UUID(value)
  File "C:\IBM\python27\Lib\uuid.py", line 133, in __init__
    hex = hex.replace('urn:', '').replace('uuid:', '')
AttributeError: 'UUID' object has no attribute 'replace'
WARNING May, 17 2017 13:43:33 smartscan            2356 948 Value id before isinstance check: 148428392
WARNING May, 17 2017 13:43:33 smartscan            2356 948 Actual type: <class 'uuid.UUID'>
WARNING May, 17 2017 13:43:33 smartscan            2356 948 Is isinstance lying? False
WARNING May, 17 2017 13:43:33 smartscan            2356 948 uuid module used: uuid
WARNING May, 17 2017 13:43:33 smartscan            2356 948 id(uuid): 43429848
WARNING May, 17 2017 13:43:33 smartscan            2356 948 id(uuid.UUID): 41308792
WARNING May, 17 2017 13:43:33 smartscan            2356 948 id(type(value)): 416421896
WARNING May, 17 2017 13:43:33 smartscan            2356 948 module file of `value` class: C:\IBM\python27\Lib\uuid.pyc
WARNING May, 17 2017 13:43:33 smartscan            2356 948 Functional isinstance? True
WARNING May, 17 2017 13:43:33 smartscan            2356 948 Functional isinstance2? True
WARNING May, 17 2017 13:43:33 smartscan            2356 948 Failed isinstance check, uuid module: C:\IBM\python27\Lib\uuid.pyc
WARNING May, 17 2017 13:43:33 smartscan            2356 948 Value id after isinstance check: 148428392
WARNING May, 17 2017 13:43:33 smartscan            2356 948 Value id before cast: 148428392
ERROR May, 17 2017 13:43:33 smartscan            2356 948 Failed cast: value type and id: <class 'uuid.UUID'>, 148428392
Traceback (most recent call last):
  File "D:\redacted\backend\env\lib\site-packages\django\db\models\fields\__init__.py", line 2425, in get_db_prep_value
    value = uuid.UUID(value)
  File "C:\IBM\python27\Lib\uuid.py", line 133, in __init__
    hex = hex.replace('urn:', '').replace('uuid:', '')
AttributeError: 'UUID' object has no attribute 'replace'

High level observations

Things go well for a while, especially when the input is indeed a string, as can be noticed from the start of the logging output. Note that on line 48 of the logging output we are indeed dealing with a uuid.UUID instance and it leads to a crash.

Restarting Apache ‘solves’ the issue for a while, until it doesn’t anymore.

Diving deeper

The uuid module to be used appears to be the right standard lib module. But, when comparing the IDs of the classes, we see an unexpected result. In a plain python shell:

>>> import uuid
>>> some_uuid = uuid.uuid4()
>>> id(type(some_uuid)) == id(uuid.UUID)
True

However, the logging output has a different result:

WARNING May, 17 2017 13:43:33 smartscan            2356 948 Actual type: <class 'uuid.UUID'>
WARNING May, 17 2017 13:43:33 smartscan            2356 948 Is isinstance lying? False
WARNING May, 17 2017 13:43:33 smartscan            2356 948 id(uuid.UUID): 41308792
WARNING May, 17 2017 13:43:33 smartscan            2356 948 id(type(value)): 416421896

The only way how I managed to reproduce a similar thing like this, is by fiddling with sys.modules, example shell session:

>>> import uuid
>>> some_uuid = uuid.uuid4()
>>> isinstance(some_uuid, uuid.UUID)
True  # as expected
>>> del uuid
>>> isinstance(some_uuid, uuid.UUID)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'uuid' is not defined  # as expected
>>> import uuid
>>> isinstance(some_uuid, uuid.UUID)
True  # as expected, since the module is loaded from the cache - `sys.modules['uuid']`
>>> import sys
>>> del sys.modules['uuid']
>>> isinstance(some_uuid, uuid.UUID)
True  # as expected, since we still have a reference in the shell session
>>> del uuid
>>> isinstance(some_uuid, uuid.UUID)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'uuid' is not defined  # as expected, name reference is dropped
>>> import uuid  # freshly loaded, since it was no longer in `sys.modules`
>>> isinstance(some_uuid, uuid.UUID)
False

Questions?

So, we’re kind of clueless on this one. What’s happening? Why does it seems like sys.modules is getting mutuated? Is there a thread-safety issue somehow?

Next steps

We’re going to try and set up an instance with Python 3 and see if the problem persists, but can’t give any timeframe on that.

About this issue

  • Original URL
  • State: closed
  • Created 7 years ago
  • Comments: 16 (5 by maintainers)

Most upvoted comments

@felipinbombin Do you have WSGIApplicationGroup set to %{GLOBAL} in your Apache config.

+3
GrahamDumpleton on Sep 21, 2018

Hi friends, Is the error solved after adding WSGIApplicationGroup %{GLOBAL} ??

+2
svb0866 on Sep 30, 2020
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