This package makes it to use UWSGI signal framework for asynchronous tasks management. It's more functional and flexible than cron scheduler, and can be used as replacement for celery in many cases.
The module works only in UWSGI web server environment, you also may have to setup some mules or\and spooler processes as described in UWSGI documentation.
Simple execute pip install uwsgi_tasks
Use case: you have Django project and want to send all emails asynchronously.
Setup some mules with --mule
or --mules=<N>
parameters, or some spooler
processes with --spooler==<path_to_spooler_folder>
.
Then write:
# myapp/__init__.py
from django.core.mail import send_mail
from uwsgi_tasks import task, TaskExecutor, set_uwsgi_callbacks
# set default callbacks for mules and spoolers
set_uwsgi_callbacks()
@task(executor=TaskExecutor.MULE)
def send_email_async(subject, body, email_to):
return send_mail(subject, body, 'noreply@domain.com', [email_to])
...
def my_view():
# Execute tasks asynchronously on first available mule
send_email_async('Welcome!', 'Thank you!', 'user@domain.com')
Execution of send_email_async
will not block execution of my_view
, since
function will be called by first available mule.
The following tasks execution backends are supported:
AUTO
- default mode, mule will be used if it is available and pickled task's arguments less than 64 KB in size, otherwise spooler will be used. If spooler is not available, than task is executed at runtime.MULE
- execute decorated task on first available muleSPOOLER
- execute decorated task on spoolerRUNTIME
- execute task at runtime
When SPOOLER
backend is used, the following additional parameters are supported:
priority
- string related to priority of this task, larger = less important, so you can simply use digits.spooler-ordered
parameter must be set for this feature to work.at
- UNIX timestamp or Python datetime or Python timedelta object.spooler_return
- boolean value,False
by default. IfTrue
is passed, you can return spooler codes from function, e.g.SPOOL_OK
,SPOOL_RETRY
andSPOOL_IGNORE
.retry_count
- how many times spooler should repeat the task if it returnsSPOOL_RETRY
code, impliesspooler_return=True
.retry_timeout
- how many seconds between attempts spooler shoud wait to execute the task. Actual timeout depends onspooler-frequency
parameter. Python timedelta object is also supported.
Use case: run task asynchronously and repeat execution 3 times at maximum if it fails, with 5 seconds timeout between attempts.
from functools import wraps
from uwsgi_tasks import task, TaskExecutor
def task_wrapper(func):
@wraps(func) # required!
def _inner(*args, **kwargs):
print 'Task started with parameters:', args, kwargs
try:
func(*args, **kwargs)
except Exception as ex: # example
print 'Exception is occurred', ex, 'repeat the task'
return uwsgi.SPOOL_RETRY
print 'Task ended', func
return uwsgi.SPOOL_OK
return _inner
@task(executor=TaskExecutor.SPOOLER, retry_count=3, retry_timeout=5)
@task_wrapper
def spooler_task(text):
print 'Hello, spooler! text =', text
raise Exception('Sorry, task failed!')
Tasks should be imported on project initialization, thus if you use Django, you may place your tasks in app/tasks.py
file and import them in app/__init__.py
:
# app/__init__.py
from .tasks import *
If Django's version is >= 1.7, you are encouraged to use AppConfig.ready
method as described in official documentation:
from importlib import import_module
from django.apps import AppConfig
class IndexConfig(AppConfig):
name = 'project.apps.index'
verbose_name = 'Just index page'
def ready(self):
import_module('.tasks', self.name)
It's necessary to setup required uwsgi callbacks at project's initialization, you should call set_uwsgi_callbacks
in your project/__init__.py
file. Don't do from uwsgidecorators import *
, otherwise you will override callbacks.
Make sure task's arguments must be pickable, since they are serialized and send via socket (mule) or file (spooler).
This API is similar to uwsgi bundled Python decorators module. One thing to note: you are not able to provide any arguments to timer-like or cron-like tasks. See examples below:
from uwsgi_tasks import *
@timer(seconds=5)
def print_every_5_seconds(signal_number):
"""Prints string every 5 seconds
Keep in mind: task is created on initialization.
"""
print 'Task for signal', signal_number
@timer(seconds=5, iterations=3, target='workers')
def print_every_5_seconds(signal_number):
"""Prints string every 5 seconds 3 times"""
print 'Task with iterations for signal', signal_number
@timer_lazy(seconds=5)
def print_every_5_seconds_after_call(signal_number):
"""Prints string every 5 seconds"""
print 'Lazy task for signal', signal_number
@cron(minute=-2)
def print_every_2_minutes(signal_number):
print 'Cron task:', signal_number
@cron_lazy(minute=-2, target='mule')
def print_every_2_minutes_after_call(signal_number):
print 'Cron task:', signal_number
...
def my_view():
print_every_5_seconds_after_call()
print_every_2_minutes_after_call()
Timer and cron decorators supports target
parameter, supported values are described here.
Keep in mind the maximum number of timer-like and cron-like tasks is 256 for each available worker.