<p dir="auto">This issue appears to be very similar to issue <a class="issue-link js-issue-link" data-error-text="Failed to load title" data-id="12542063" data-permission-text="Title is private" data-url="https://github.com/celery/celery/issues/1263" data-hovercard-type="issue" data-hovercard-url="/celery/celery/issues/1263/hovercard" href="https://github.com/celery/celery/issues/1263">#1263</a> .</p>
<p dir="auto">I'm running celery 3.0.21 on both a Window XP and Linux virtual machine.  Whenever a task is dispatched to the Windows VM, I will get the same error as reported in <a class="issue-link js-issue-link" data-error-text="Failed to load title" data-id="12542063" data-permission-text="Title is private" data-url="https://github.com/celery/celery/issues/1263" data-hovercard-type="issue" data-hovercard-url="/celery/celery/issues/1263/hovercard" href="https://github.com/celery/celery/issues/1263">#1263</a>, which was reported fixed in 3.0.18.  When the same task is dispatched to the Linux VM, no error occurs.</p>
<p dir="auto">Here's some output from the Windows VM:</p>
<div class="snippet-clipboard-content notranslate position-relative overflow-auto" data-snippet-clipboard-copy-content="[2013-08-07 22:24:32,887: DEBUG/MainProcess] Task accepted: scanworker.tasks.pan
da[ca2db5cc-37a6-4b61-b5a0-c7a414494b10] pid:3700
[2013-08-07 22:24:32,887: ERROR/MainProcess] Task scanworker.tasks.panda[ca2db5c
c-37a6-4b61-b5a0-c7a414494b10] raised exception: Task of kind 'scanworker.tasks.
panda' is not registered, please make sure it's imported.
Traceback (most recent call last):
  File &quot;c:\msvirtualenv\lib\site-packages\billiard\pool.py&quot;, line 311, in worker

    result = (True, func(*args, **kwds))
  File &quot;c:\msvirtualenv\lib\site-packages\celery\task\trace.py&quot;, line 325, in _f
ast_trace_task
    return _tasks[task].__trace__(uuid, args, kwargs, request)[0]
  File &quot;c:\msvirtualenv\lib\site-packages\celery\app\registry.py&quot;, line 20, in _
_missing__
    raise self.NotRegistered(key)
NotRegistered: 'scanworker.tasks.panda'"><pre class="notranslate"><code class="notranslate">[2013-08-07 22:24:32,887: DEBUG/MainProcess] Task accepted: scanworker.tasks.pan
da[ca2db5cc-37a6-4b61-b5a0-c7a414494b10] pid:3700
[2013-08-07 22:24:32,887: ERROR/MainProcess] Task scanworker.tasks.panda[ca2db5c
c-37a6-4b61-b5a0-c7a414494b10] raised exception: Task of kind 'scanworker.tasks.
panda' is not registered, please make sure it's imported.
Traceback (most recent call last):
  File "c:\msvirtualenv\lib\site-packages\billiard\pool.py", line 311, in worker

    result = (True, func(*args, **kwds))
  File "c:\msvirtualenv\lib\site-packages\celery\task\trace.py", line 325, in _f
ast_trace_task
    return _tasks[task].__trace__(uuid, args, kwargs, request)[0]
  File "c:\msvirtualenv\lib\site-packages\celery\app\registry.py", line 20, in _
_missing__
    raise self.NotRegistered(key)
NotRegistered: 'scanworker.tasks.panda'
</code></pre></div>
<p dir="auto">celeryctl believes that the task is, in fact, registered on the Windows VM, so there's a discrepancy here.  vmuser-1c6d67f6 in the following printout refers to the Windows VM.</p>
<div class="snippet-clipboard-content notranslate position-relative overflow-auto" data-snippet-clipboard-copy-content="(msvirtualenv)vagrant@precise64:~/MassScan$ DJANGO_SETTINGS_MODULE=scaggr.settings_dev celeryctl inspect registered --config=masterceleryconfig
[ SNIP ] 
-&gt; vmuser-1c6d67f6: OK
[ SNIP ]
    * scanworker.tasks.panda [routing_key=panda]
[ SNIP ]"><pre class="notranslate"><code class="notranslate">(msvirtualenv)vagrant@precise64:~/MassScan$ DJANGO_SETTINGS_MODULE=scaggr.settings_dev celeryctl inspect registered --config=masterceleryconfig
[ SNIP ] 
-&gt; vmuser-1c6d67f6: OK
[ SNIP ]
    * scanworker.tasks.panda [routing_key=panda]
[ SNIP ]
</code></pre></div>
<p dir="auto">The same output appears in the terminal window for both the VM generating the tasks (a Linux VM) as well as the terminal window on the Windows VM that is receiving the tasks.  All outputs resulting from celeryctl indicate that the "scanworker.tasks.panda" task is registered.</p>
<p dir="auto">Thanks for taking a look!</p>
<p dir="auto">Hi,</p>
<p dir="auto">After upgrading Celery to 3.0.13, all tasks break showing the following message:</p>
<div class="snippet-clipboard-content notranslate position-relative overflow-auto" data-snippet-clipboard-copy-content="[2013-01-08 15:22:25,405: ERROR/MainProcess] Task varnish_bans_manager.core.tasks.bans.Submit[43fb4a02-887f-456d-8326-1c02c1c9faa2] raised exception: Task of kind 'varnish_bans_manager.core.tasks.bans.Submit' is not registered, please make sure it's imported.
Traceback (most recent call last):
  File &quot;/home/user/.virtualenvs/vbm/lib/python2.6/site-packages/billiard/pool.py&quot;, line 301, in worker
    result = (True, func(*args, **kwds))
  File &quot;/home/user/.virtualenvs/vbm/lib/python2.6/site-packages/celery/task/trace.py&quot;, line 312, in _fast_trace_task
    return _tasks[task].__trace__(uuid, args, kwargs, request)[0]
  File &quot;/home/user/.virtualenvs/vbm/lib/python2.6/site-packages/celery/app/registry.py&quot;, line 20, in __missing__
    raise self.NotRegistered(key)
NotRegistered: 'varnish_bans_manager.core.tasks.bans.Submit'"><pre class="notranslate"><code class="notranslate">[2013-01-08 15:22:25,405: ERROR/MainProcess] Task varnish_bans_manager.core.tasks.bans.Submit[43fb4a02-887f-456d-8326-1c02c1c9faa2] raised exception: Task of kind 'varnish_bans_manager.core.tasks.bans.Submit' is not registered, please make sure it's imported.
Traceback (most recent call last):
  File "/home/user/.virtualenvs/vbm/lib/python2.6/site-packages/billiard/pool.py", line 301, in worker
    result = (True, func(*args, **kwds))
  File "/home/user/.virtualenvs/vbm/lib/python2.6/site-packages/celery/task/trace.py", line 312, in _fast_trace_task
    return _tasks[task].__trace__(uuid, args, kwargs, request)[0]
  File "/home/user/.virtualenvs/vbm/lib/python2.6/site-packages/celery/app/registry.py", line 20, in __missing__
    raise self.NotRegistered(key)
NotRegistered: 'varnish_bans_manager.core.tasks.bans.Submit'
</code></pre></div>
<ul dir="auto">
<li><code class="notranslate">CELERY_IMPORTS</code> and all obvious stuff is correctly configured (at least, it has been working correctly for some months).</li>
<li>Downgrading to 3.0.12, everything works fine again.</li>
<li>Staying in 3.0.13 and using a Redis backend also fixes the problem.</li>
<li>However, staying in 3.0.13 and using a Django DB backend (i.e. <code class="notranslate">BROKER_URL = 'django://'</code>) is broken for some reason.</li>
</ul>
<p dir="auto">Any clues? Thanks!</p>