There are a couple of issue:

* The reactor is already running and kernel.client tries to start it.

* The sync code in kernel.client has to be run in a different thread
from the main reactor.  When you use kernel.client in IPython, it
actually starts the twisted reactor in a thread.  The make the client
work in the engine, we need to run the users code (where the client
will be used) in a different thread from the reactor.

* To do this, parts of the engine have to be made threadsafe.

I haven't though about using the asyncclient though in the engine.  It
may work, but as you guess, there may be complications.

Cheers,

Brian

On Fri, Apr 24, 2009 at 11:35 AM, Vishal Vatsa <email address hidden> wrote:
> Just wondering, if the problem is that there is already another reactor
> running so can't we just use the asyncclient.
>
> I ran this StringTask:
> "from IPython.kernel import asyncclient ; doc_str = asyncclient.__docformat__"
>
> I am sure using asyncclient has its own set of complications.
>
> -vishal
>
> 2009/4/14 Brian Granger <email address hidden>:
>> Fixing this will require that the core be thread safe and that the
>> reactor runs in a different thread from user code.  This should happen
>> this summer.
>>
>> ** Changed in: ipython
>>   Importance: Undecided => Medium
>>
>> ** Changed in: ipython
>>       Status: New => Confirmed
>>
>> ** Changed in: ipython
>>     Assignee: (unassigned) => Brian Granger (ellisonbg)
>>
>> --
>> IPython.kernel.client cannot be imported inside an engine
>> https://bugs.launchpad.net/bugs/300218
>> You received this bug notification because you are a member of IPython
>> Developers, which is subscribed to IPython.
>>
>> Status in IPython - Enhanced Interactive Python: Confirmed
>>
>> Bug description:
>> Importing IPython.kernel.client in an engine doesn't work.
>> The twisted reactor is started for the controller and engine
>> automatically when they start and for the client when
>> IPython.kernel.client is imported. The problem is that when executing import
>> IPython.kernel.client script in the engine, the engine already has the reactor running,
>> and the import tries to start the reactor again. This causes
>> a the ipengine<->ipcontroller communication to fail on
>> subsequently executed commands.
>>
>> A typical use case when one needs to import IPython.kernel.client in the
>> engines, is when one wants to use one of the engines as a  client connected
>> to another ipcontroller, and it seems impossible to do it,
>> if one cannot import the client in one of the engines.
>>
>
> --
> IPython.kernel.client cannot be imported inside an engine
> https://bugs.launchpad.net/bugs/300218
> You received this bug notification because you are a member of IPython
> Developers, which is subscribed to IPython.
>
> Status in IPython - Enhanced Interactive Python: Confirmed
>
> Bug description:
> Importing IPython.kernel.client in an engine doesn't work.
> The twisted reactor is started for the controller and engine
> automatically when they start and for the client when
> IPython.kernel.client is imported. The problem is that when executing import
> IPython.kernel.client script in the engine, the engine already has the reactor running,
> and the import tries to start the reactor again. This causes
> a the ipengine<->ipcontroller communication to fail on
> subsequently executed commands.
>
> A typical use case when one needs to import IPython.kernel.client in the
> engines, is when one wants to use one of the engines as a  client connected
> to another ipcontroller, and it seems impossible to do it,
> if one cannot import the client in one of the engines.
>



-- 
Brian E. Granger, Ph.D.
Assistant Professor of Physics
Cal Poly State University, San Luis Obispo
<email address hidden>
<email address hidden>