django - Celery Task the difference between these two tasks below -

what's difference between these 2 tasks below?

the first 1 gives error, second 1 runs fine. both same, accept arguments , both called in same way.

processrequests.delay(batch) **error object.__new__() takes no parameters**   sendmessage.delay(message.pk, self.pk) **works!!!!**    

now, have been made aware of error means, confusion why 1 works , not other.

tasks...

1)

class processrequests(task):     name = "request process"     max_retries = 1     default_retry_delay = 3      def run(self, batch):        #do 

2)

class sendmessage(task):     name = "sending sms"     max_retries = 10     default_retry_delay = 3      def run(self, message_id, gateway_id=none, **kwargs):         #do 

full task code....

from celery.task import task celery.decorators import task  import logging  sms.models import message, gateway, batch contacts.models import contact accounts.models import transaction, account   class sendmessage(task):     name = "sending sms"     max_retries = 10     default_retry_delay = 3      def run(self, message_id, gateway_id=none, **kwargs):         logging.debug("about send message.")          # because don't have control on transactions         # in our calling code, retry 10 times, every 3         # seconds, in order try allow commit database         # finish. gives server 30 seconds write of         # data database, , finish view.         try:             message = message.objects.get(pk=message_id)         except exception exc:             raise sendmessage.retry(exc=exc)           if not gateway_id:             if hasattr(message.billee, 'sms_gateway'):                 gateway = message.billee.sms_gateway             else:                 gateway = gateway.objects.all()[0]         else:             gateway = gateway.objects.get(pk=gateway_id)          # check have credits sent me message         account = account.objects.get(user=message.sender)         # i'm getting non-cathed version here, check performance!!!!!         if account._balance() >= message.length:             response = gateway._send(message)              if response.status == 'sent':                 # take credit users account.                 transaction = transaction(                     account=account,                     amount=- message.charge,                     description="debit: sms sent",                      )                 transaction.save()                 message.billed = true                 message.save()         else:             pass           logging.debug("done sending message.")   class processrequests(task):     name = "request process"     max_retries = 1     default_retry_delay = 3      def run(self, message_batch):         e in contact.objects.filter(contact_owner=message_batch.user, group=message_batch.group):             msg = message.objects.create(                 recipient_number=e.mobile,                 content=message_batch.content,                 sender=e.contact_owner,                 billee=message_batch.user,                 sender_name=message_batch.sender_name             )             gateway = gateway.objects.get(pk=2)             msg.send(gateway)             #replace('[firstname]', e.first_name) 

tried:

 processrequests.delay(batch) should work gives error error object.__new__() takes no parameters       processrequests().delay(batch) gives error error object.__new__() takes no parameters 

i able reproduce issue:

import celery celery.task import task  @celery.task class foo(celery.task):     name = "foo"     def run(self, batch):        print 'foo'  class bar(celery.task):     name = "bar"     def run(self, batch):        print 'bar'  # subclass deprecated base task class class bar2(task):     name = "bar2"     def run(self, batch):        print 'bar2'  @celery.task(name='def-foo') def foo(batch):     print 'foo' 

output:

in [2]: foo.delay('x') [warning/poolworker-4] foo  in [3]: foo().delay('x') [warning/poolworker-2] foo  in [4]: bar().delay('x') [warning/poolworker-3] bar  in [5]: foo.delay('x') typeerror: object.__new__() takes no parameters  in [6]: bar.delay('x') typeerror: unbound method delay() must called bar instance first argument (got str instance instead)  in [7]: bar2.delay('x') [warning/poolworker-1] bar2 

i see use deprecated celery.task.task base class, why don't unbound method errors:

definition: task(self, *args, **kwargs) docstring: deprecated task base class.  modern applications should use :class:`celery.task` instead. 

i don't know why processrequests doesn't work though. maybe caching issues, may have tried apply decorator class before , got cached, , error when try apply decorator task class.

delete .pyc file, restart celery workers , try again.

don't use classes directly

1. tasks instantiated once per (worker) process, creating objects of task classes (on client-side) every time doesn't make sense, i.e. bar() wrong.
2. foo.delay() or foo().delay() might or might not work, depends on combination of decorator name argument , class name attribute.

get task object celery.registry.tasks dictionary or use @celery.task decorator on functions (foo in example) instead.