Trying to use django_scheduled_tasks, but unable to migrate

Using Django Mystery Errors
1

Hi, I want to run scheduled task on my server, so I try to install django_scheduled_tasks:

INSTALLED_APPS = [
    .
    .
    .
    'django_scheduled_tasks',
    .
    .
    .
]

but when running python3 manage.py migrate, the command fails (just show last few lines in terminal for simple):

.
.
.
File "(my private path)|cursors.py", line 330, in _query
    db.query(q)
    ~~~~~~~~^^^
  File "(my private path)|connections.py", line 286, in query
    _mysql.connection.query(self, query)
    ~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^
django.db.utils.OperationalError: (1170, "BLOB/TEXT column 'task_hash' used in key specification without a key length")

What is the problem (my project is using MySQL)?

2

When requesting assistance with an issue, please post the complete traceback along with all other output generated by the command.

3

Additionally, please specific what versions of Python and Django you are using, along with the versions of any third-party apps identified in the project.

4

Hi, just retried using a new virtual world testworld and testproject with the following commands:

python3 -m venv testworld
cd testworld
source bin/activate
python -m pip install Django
export MYSQLCLIENT_CFLAGS="-I/usr/local/mysql/include"
export MYSQLCLIENT_LDFLAGS="-L/usr/local/mysql/lib -lmysqlclient"
pip install mysqlclient
pip install django_scheduled_tasks
django-admin startproject testproject

then I modify testproject/testproject/settings.py to specify this project use mysql and django_scheduled_tasks :

.
.
.
INSTALLED_APPS = [
    'django.contrib.admin',
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.messages',
    'django.contrib.staticfiles',
    'django_scheduled_tasks'
]
.
.
.
DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.mysql',
        'NAME': (private),
        'USER': (private),              # Your MySQL username
        'PASSWORD': (private),  # Your MySQL password
        'HOST': (private),         # Or your server IP
        'PORT': (private),              # Default MySQL port
    }
}
.
.
.

when running command python3 manage.py makemigrations , it seems look normal, but when running python3 manage.py migrate, the following error occurs:

Operations to perform:
  Apply all migrations: admin, auth, contenttypes, django_scheduled_tasks, sessions
Running migrations:
  Applying django_scheduled_tasks.0001_initial...Traceback (most recent call last):
  File "/Users/testuser/Desktop/testworld/lib/python3.14/site-packages/django/db/backends/utils.py", line 103, in _execute
    return self.cursor.execute(sql)
           ~~~~~~~~~~~~~~~~~~~^^^^^
  File "/Users/testuser/Desktop/testworld/lib/python3.14/site-packages/django/db/backends/mysql/base.py", line 78, in execute
    return self.cursor.execute(query, args)
           ~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^
  File "/Users/testuser/Desktop/testworld/lib/python3.14/site-packages/MySQLdb/cursors.py", line 179, in execute
    res = self._query(mogrified_query)
  File "/Users/testuser/Desktop/testworld/lib/python3.14/site-packages/MySQLdb/cursors.py", line 330, in _query
    db.query(q)
    ~~~~~~~~^^^
  File "/Users/testuser/Desktop/testworld/lib/python3.14/site-packages/MySQLdb/connections.py", line 286, in query
    _mysql.connection.query(self, query)
    ~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^
MySQLdb.OperationalError: (1170, "BLOB/TEXT column 'task_hash' used in key specification without a key length")

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/Users/testuser/Desktop/testworld/testproject/manage.py", line 22, in <module>
    main()
    ~~~~^^
  File "/Users/testuser/Desktop/testworld/testproject/manage.py", line 18, in main
    execute_from_command_line(sys.argv)
    ~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^
  File "/Users/testuser/Desktop/testworld/lib/python3.14/site-packages/django/core/management/__init__.py", line 443, in execute_from_command_line
    utility.execute()
    ~~~~~~~~~~~~~~~^^
  File "/Users/testuser/Desktop/testworld/lib/python3.14/site-packages/django/core/management/__init__.py", line 437, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^
  File "/Users/testuser/Desktop/testworld/lib/python3.14/site-packages/django/core/management/base.py", line 420, in run_from_argv
    self.execute(*args, **cmd_options)
    ~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/testuser/Desktop/testworld/lib/python3.14/site-packages/django/core/management/base.py", line 464, in execute
    output = self.handle(*args, **options)
  File "/Users/testuser/Desktop/testworld/lib/python3.14/site-packages/django/core/management/base.py", line 111, in wrapper
    res = handle_func(*args, **kwargs)
  File "/Users/testuser/Desktop/testworld/lib/python3.14/site-packages/django/core/management/commands/migrate.py", line 354, in handle
    post_migrate_state = executor.migrate(
        targets,
    ...<3 lines>...
        fake_initial=fake_initial,
    )
  File "/Users/testuser/Desktop/testworld/lib/python3.14/site-packages/django/db/migrations/executor.py", line 137, in migrate
    state = self._migrate_all_forwards(
        state, plan, full_plan, fake=fake, fake_initial=fake_initial
    )
  File "/Users/testuser/Desktop/testworld/lib/python3.14/site-packages/django/db/migrations/executor.py", line 169, in _migrate_all_forwards
    state = self.apply_migration(
        state, migration, fake=fake, fake_initial=fake_initial
    )
  File "/Users/testuser/Desktop/testworld/lib/python3.14/site-packages/django/db/migrations/executor.py", line 257, in apply_migration
    state = migration.apply(state, schema_editor)
  File "/Users/testuser/Desktop/testworld/lib/python3.14/site-packages/django/db/migrations/migration.py", line 132, in apply
    operation.database_forwards(
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~^
        self.app_label, schema_editor, old_state, project_state
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    )
    ^
  File "/Users/testuser/Desktop/testworld/lib/python3.14/site-packages/django/db/migrations/operations/models.py", line 100, in database_forwards
    schema_editor.create_model(model)
    ~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^
  File "/Users/testuser/Desktop/testworld/lib/python3.14/site-packages/django/db/backends/base/schema.py", line 513, in create_model
    self.execute(sql, params or None)
    ~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^
  File "/Users/testuser/Desktop/testworld/lib/python3.14/site-packages/django/db/backends/base/schema.py", line 205, in execute
    cursor.execute(sql, params)
    ~~~~~~~~~~~~~~^^^^^^^^^^^^^
  File "/Users/testuser/Desktop/testworld/lib/python3.14/site-packages/django/db/backends/utils.py", line 122, in execute
    return super().execute(sql, params)
           ~~~~~~~~~~~~~~~^^^^^^^^^^^^^
  File "/Users/testuser/Desktop/testworld/lib/python3.14/site-packages/django/db/backends/utils.py", line 79, in execute
    return self._execute_with_wrappers(
           ~~~~~~~~~~~~~~~~~~~~~~~~~~~^
        sql, params, many=False, executor=self._execute
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    )
    ^
  File "/Users/testuser/Desktop/testworld/lib/python3.14/site-packages/django/db/backends/utils.py", line 92, in _execute_with_wrappers
    return executor(sql, params, many, context)
  File "/Users/testuser/Desktop/testworld/lib/python3.14/site-packages/django/db/backends/utils.py", line 100, in _execute
    with self.db.wrap_database_errors:
         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/testuser/Desktop/testworld/lib/python3.14/site-packages/django/db/utils.py", line 94, in __exit__
    raise dj_exc_value.with_traceback(traceback) from exc_value
  File "/Users/testuser/Desktop/testworld/lib/python3.14/site-packages/django/db/backends/utils.py", line 103, in _execute
    return self.cursor.execute(sql)
           ~~~~~~~~~~~~~~~~~~~^^^^^
  File "/Users/testuser/Desktop/testworld/lib/python3.14/site-packages/django/db/backends/mysql/base.py", line 78, in execute
    return self.cursor.execute(query, args)
           ~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^
  File "/Users/testuser/Desktop/testworld/lib/python3.14/site-packages/MySQLdb/cursors.py", line 179, in execute
    res = self._query(mogrified_query)
  File "/Users/testuser/Desktop/testworld/lib/python3.14/site-packages/MySQLdb/cursors.py", line 330, in _query
    db.query(q)
    ~~~~~~~~^^^
  File "/Users/testuser/Desktop/testworld/lib/python3.14/site-packages/MySQLdb/connections.py", line 286, in query
    _mysql.connection.query(self, query)
    ~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^
django.db.utils.OperationalError: (1170, "BLOB/TEXT column 'task_hash' used in key specification without a key length")

Note : when the project just use default sqlite instead of mysql , python3 manage.py migrate is ok.

python version : Python 3.14.5

pip list (including version of django-scheduled-tasks):

annotated-types        0.7.0
asgiref                3.11.1
cron-converter         1.3.1
Django                 6.0.5
django-scheduled-tasks 0.2.18
django-stubs-ext       6.0.4
django-tasks           0.12.0
mysqlclient            2.2.8
pip                    26.1.1
pydantic               2.13.4
pydantic_core          2.46.4
pydantic-extra-types   2.11.1
python-dateutil        2.9.0.post0
six                    1.17.0
sqlparse               0.5.5
typing_extensions      4.15.0
typing-inspection      0.4.2

os : macOS 13.7.8

Note : Originally I want to use django_scheduled_tasks to clear expired sessions regularly, but after retrying installing several times I gave up and decided just using _thread to do my task at AppConfig:

from django.apps import AppConfig
import time
import _thread
from datetime import datetime
class CoreConfig(AppConfig):
    default_auto_field = 'django.db.models.BigAutoField'
    name = 'core'
    def ready(self):

        #clean expired tokens every 5 minutes
        from django.contrib.sessions.models import Session
        def cron_job_clean_expired_tokens():
            try:
                for session in list(Session.objects.iterator()):
                    if session.expire_date.timestamp() < datetime.now().timestamp():
                        session.delete()
            except Exception as e:
                print("cron job exception : " + str(e))
            time.sleep(300)
            cron_job_clean_expired_tokens()
        _thread.start_new_thread(cron_job_clean_expired_tokens,())
5

(error snipped)

If it works for sqlite but not for mysql, then I think your next step would be to file an issue on the django_scheduled_tasks site.

Side note:

This is an extremely bad idea for any project looking to be deployed in a production-quality deployment. (You can find many threads here in the forum explaining why running your own tasks is unwise.)

Also note that Django provides a management command clearsessions precisely for this purpose. For your purposes here, I would recommend using this with whatever other work you might want to do as a cron job. (See Clearing the session store)