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Error: SynchronousOnlyOperation with Django 3

See original GitHub issue

I have Ubuntu 18.04. I’ve followed the instructions in the README, but when I run python manage.py livereload and open localhost:8000 I get a SynchronousOnlyOperation error. My traceback is as follows. It seems to raise error at {% user.is_authenticated %} template tag.

Environment:


Request Method: GET
Request URL: http://localhost:8000/

Django Version: 3.1
Python Version: 3.6.9
Installed Applications:
['livereload',
 'formsapp',
 'Dummy',
 'crispy_forms',
 'users',
 'django.contrib.admin',
 'django.contrib.auth',
 'django.contrib.contenttypes',
 'django.contrib.sessions',
 'django.contrib.messages',
 'django.contrib.staticfiles',
 'django.contrib.sites',
 'allauth',
 'allauth.account',
 'allauth.socialaccount',
 'allauth.socialaccount.providers.facebook',
 'allauth.socialaccount.providers.github',
 'allauth.socialaccount.providers.google']
Installed Middleware:
['django.middleware.security.SecurityMiddleware',
 'django.contrib.sessions.middleware.SessionMiddleware',
 'django.middleware.common.CommonMiddleware',
 'django.middleware.csrf.CsrfViewMiddleware',
 'django.contrib.auth.middleware.AuthenticationMiddleware',
 'django.contrib.messages.middleware.MessageMiddleware',
 'django.middleware.clickjacking.XFrameOptionsMiddleware']


Template error:
In template /home/raphaelnazirullah/Documents/Mental Health Web app/mental_health_app/formsapp/templates/forms/base.html, error at line 18
   You cannot call this from an async context - use a thread or sync_to_async.
   8 :     <meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">
   9 : 
   10 :     <title>{% block title %}Home page{% endblock %}</title>
   11 :     <link rel="stylesheet" href="{% static 'css/bootstrap.min.css' %}">
   12 :     <link rel="stylesheet" href="{% static 'css/styles.css' %}">
   13 : </head>
   14 : <body>
   15 : <header>
   16 :     <div>
   17 :         <!-- User login/logout options -->
   18 :          {% if user.is_authenticated %} 
   19 :             <a href="{% url 'logout' %}">Sign out</a>
   20 :         {% else %}
   21 :             <a href="{% url 'login' %}">Sign In</a>
   22 :             <a href="{% url 'register' %}">Sign Up</a>
   23 :         {% endif %}
   24 :         User: {{ user }}
   25 :     </div>
   26 :     <h1>
   27 :         <a id="logo" href="{% url 'home-page' %}">Website name & logo</a>
   28 :     </h1>


Traceback (most recent call last):
  File "/home/raphaelnazirullah/Documents/Mental Health Web app/mental_health_app/venv/lib/python3.6/site-packages/django/contrib/sessions/backends/base.py", line 215, in _get_session
    return self._session_cache

During handling of the above exception ('SessionStore' object has no attribute '_session_cache'), another exception occurred:
  File "/home/raphaelnazirullah/Documents/Mental Health Web app/mental_health_app/venv/lib/python3.6/site-packages/django/core/handlers/exception.py", line 47, in inner
    response = get_response(request)
  File "/home/raphaelnazirullah/Documents/Mental Health Web app/mental_health_app/venv/lib/python3.6/site-packages/django/core/handlers/base.py", line 179, in _get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "/home/raphaelnazirullah/Documents/Mental Health Web app/mental_health_app/formsapp/views.py", line 10, in show_homepage
    return render(request, 'forms/base.html')
  File "/home/raphaelnazirullah/Documents/Mental Health Web app/mental_health_app/venv/lib/python3.6/site-packages/django/shortcuts.py", line 19, in render
    content = loader.render_to_string(template_name, context, request, using=using)
  File "/home/raphaelnazirullah/Documents/Mental Health Web app/mental_health_app/venv/lib/python3.6/site-packages/django/template/loader.py", line 62, in render_to_string
    return template.render(context, request)
  File "/home/raphaelnazirullah/Documents/Mental Health Web app/mental_health_app/venv/lib/python3.6/site-packages/django/template/backends/django.py", line 61, in render
    return self.template.render(context)
  File "/home/raphaelnazirullah/Documents/Mental Health Web app/mental_health_app/venv/lib/python3.6/site-packages/django/template/base.py", line 170, in render
    return self._render(context)
  File "/home/raphaelnazirullah/Documents/Mental Health Web app/mental_health_app/venv/lib/python3.6/site-packages/django/template/base.py", line 162, in _render
    return self.nodelist.render(context)
  File "/home/raphaelnazirullah/Documents/Mental Health Web app/mental_health_app/venv/lib/python3.6/site-packages/django/template/base.py", line 938, in render
    bit = node.render_annotated(context)
  File "/home/raphaelnazirullah/Documents/Mental Health Web app/mental_health_app/venv/lib/python3.6/site-packages/django/template/base.py", line 905, in render_annotated
    return self.render(context)
  File "/home/raphaelnazirullah/Documents/Mental Health Web app/mental_health_app/venv/lib/python3.6/site-packages/django/template/defaulttags.py", line 305, in render
    match = condition.eval(context)
  File "/home/raphaelnazirullah/Documents/Mental Health Web app/mental_health_app/venv/lib/python3.6/site-packages/django/template/defaulttags.py", line 889, in eval
    return self.value.resolve(context, ignore_failures=True)
  File "/home/raphaelnazirullah/Documents/Mental Health Web app/mental_health_app/venv/lib/python3.6/site-packages/django/template/base.py", line 671, in resolve
    obj = self.var.resolve(context)
  File "/home/raphaelnazirullah/Documents/Mental Health Web app/mental_health_app/venv/lib/python3.6/site-packages/django/template/base.py", line 796, in resolve
    value = self._resolve_lookup(context)
  File "/home/raphaelnazirullah/Documents/Mental Health Web app/mental_health_app/venv/lib/python3.6/site-packages/django/template/base.py", line 829, in _resolve_lookup
    current = current[bit]
  File "/home/raphaelnazirullah/Documents/Mental Health Web app/mental_health_app/venv/lib/python3.6/site-packages/django/utils/functional.py", line 240, in inner
    self._setup()
  File "/home/raphaelnazirullah/Documents/Mental Health Web app/mental_health_app/venv/lib/python3.6/site-packages/django/utils/functional.py", line 376, in _setup
    self._wrapped = self._setupfunc()
  File "/home/raphaelnazirullah/Documents/Mental Health Web app/mental_health_app/venv/lib/python3.6/site-packages/django/contrib/auth/middleware.py", line 23, in <lambda>
    request.user = SimpleLazyObject(lambda: get_user(request))
  File "/home/raphaelnazirullah/Documents/Mental Health Web app/mental_health_app/venv/lib/python3.6/site-packages/django/contrib/auth/middleware.py", line 11, in get_user
    request._cached_user = auth.get_user(request)
  File "/home/raphaelnazirullah/Documents/Mental Health Web app/mental_health_app/venv/lib/python3.6/site-packages/django/contrib/auth/__init__.py", line 174, in get_user
    user_id = _get_user_session_key(request)
  File "/home/raphaelnazirullah/Documents/Mental Health Web app/mental_health_app/venv/lib/python3.6/site-packages/django/contrib/auth/__init__.py", line 58, in _get_user_session_key
    return get_user_model()._meta.pk.to_python(request.session[SESSION_KEY])
  File "/home/raphaelnazirullah/Documents/Mental Health Web app/mental_health_app/venv/lib/python3.6/site-packages/django/contrib/sessions/backends/base.py", line 65, in __getitem__
    return self._session[key]
  File "/home/raphaelnazirullah/Documents/Mental Health Web app/mental_health_app/venv/lib/python3.6/site-packages/django/contrib/sessions/backends/base.py", line 220, in _get_session
    self._session_cache = self.load()
  File "/home/raphaelnazirullah/Documents/Mental Health Web app/mental_health_app/venv/lib/python3.6/site-packages/django/contrib/sessions/backends/db.py", line 43, in load
    s = self._get_session_from_db()
  File "/home/raphaelnazirullah/Documents/Mental Health Web app/mental_health_app/venv/lib/python3.6/site-packages/django/contrib/sessions/backends/db.py", line 34, in _get_session_from_db
    expire_date__gt=timezone.now()
  File "/home/raphaelnazirullah/Documents/Mental Health Web app/mental_health_app/venv/lib/python3.6/site-packages/django/db/models/manager.py", line 85, in manager_method
    return getattr(self.get_queryset(), name)(*args, **kwargs)
  File "/home/raphaelnazirullah/Documents/Mental Health Web app/mental_health_app/venv/lib/python3.6/site-packages/django/db/models/query.py", line 425, in get
    num = len(clone)
  File "/home/raphaelnazirullah/Documents/Mental Health Web app/mental_health_app/venv/lib/python3.6/site-packages/django/db/models/query.py", line 269, in __len__
    self._fetch_all()
  File "/home/raphaelnazirullah/Documents/Mental Health Web app/mental_health_app/venv/lib/python3.6/site-packages/django/db/models/query.py", line 1303, in _fetch_all
    self._result_cache = list(self._iterable_class(self))
  File "/home/raphaelnazirullah/Documents/Mental Health Web app/mental_health_app/venv/lib/python3.6/site-packages/django/db/models/query.py", line 53, in __iter__
    results = compiler.execute_sql(chunked_fetch=self.chunked_fetch, chunk_size=self.chunk_size)
  File "/home/raphaelnazirullah/Documents/Mental Health Web app/mental_health_app/venv/lib/python3.6/site-packages/django/db/models/sql/compiler.py", line 1152, in execute_sql
    cursor = self.connection.cursor()
  File "/home/raphaelnazirullah/Documents/Mental Health Web app/mental_health_app/venv/lib/python3.6/site-packages/django/utils/asyncio.py", line 24, in inner
    raise SynchronousOnlyOperation(message)

Exception Type: SynchronousOnlyOperation at /
Exception Value: You cannot call this from an async context - use a thread or sync_to_async.

My project structure is as follows:

.
├── db.sqlite3
├── Dummy
├── formsapp
├── manage.py
├── mental_health_app
├── my-cred.txt
├── __pycache__
├── README.md
├── requirements.txt
├── users
├── venv

Issue Analytics

  • State:open
  • Created 3 years ago
  • Reactions:2
  • Comments:6

github_iconTop GitHub Comments

1reaction
lingstercommented, Apr 2, 2021

I had a similar problem and managed to work around as per suggestion here: https://docs.djangoproject.com/en/3.1/topics/async/#async-safety ie defined an environment variable: DJANGO_ALLOW_ASYNC_UNSAFE=1

note this should only be done in a local non-production/development environment or you could risk losing/corrupting data.

In my case I am running a project created using django 3.1.7 and python 3.8.8

0reactions
pradyunsgcommented, Feb 3, 2022

You really shouldn’t be using livereload in production.

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