Hi,
all in all it is quite simple. As you already noted, the context manager is
just syntactical sugar. I really only need id to hide complexity from our
customers.
So, how does the migration work:
The originating side runs tasklet t1.
def f():
do_local_work()
with get_context_manager():
do_remote_work()
more_local_work()
t1=tasklet(f)()
The context manager delegates the work to the main tasklet.
It looks roughly looks like
def __enter__(self):
stackless.schedule_remove(self) # (1)
return None
def __exit__(self, exc_type, exc_value, traceback):
tmp = stackless.schedule_remove((self, exc_type, exc_value, traceback)) # (2)
return self.end_exit(tmp)
After __enter__ transferred control back to the main tasklet, the main tasklet
- pickles (t1, additional data), result is string p1
- unbinds t1: t1.bind(None)
- uses RPyC to run p on the remote site
The remote side:
- unpickles p1, result is tasklet t2
- t2.insert()
- stackless.run()
- t2 runs till (2)
- the remote side now pickles t2, result is string p2
- t2.bind(None)
- t2 = None
- return p2 to the originating side
The originating side
- unpickles p2, result is tasklet t3
- replaces the original t1 by t3: t1 = t3
- deletes t3: t3 = None
- continues t1: t1.insert(); stackless.run()
I use the extended pickler form the sPickle library. This pickler can replace
certain resource-objects (i.e. open files) by RPyC-Proxy objects on the fly.
Cheers
Anselm
Am 05.09.2013 08:48, schrieb Kristján Valur Jónsson:
> Hi,
> I think this is a better spot to discuss this topic than the checkin comments
> in Anselm's repo:
> https://bitbucket.org/akruis/fg2python/commits/852868afc498e800e4091e83aa818bf5d7b35939#comment-406276
>
> So, Anselm said:
>
> Sorry for the delayed answer, here is the use case.
>
> I tried to write a context manager that changes the execution host of the
> body. In __enter__ I pickle the tasklet and transfer the pickle to another
> process and unpickle it there. Then the tasklet executes until it calls
> __exit__. In exit I pickle it again and transfer it back to the original
> process.
>
> This is really interesting. How did it pan out? Also, How does it work on
> the originating site? A context manager does not (currently) allow the body
> code to be skipped, which I presume is what must happen on the "source" side.
> (although, this here patch<http://bugs.python.org/issue18677> would allow
> that)
>
> I'm very much a fan of context managers these days. I just added
> stackless.atomic(), a built-in to provide performance for this ubiquitous
> thing.
>
>
>
> Hi,
>
> I think this is a better spot to discuss this topic than the checkin
> comments in Anselm’s repo:
>
> https://bitbucket.org/akruis/fg2python/commits/852868afc498e800e4091e83aa818bf5d7b35939#comment-406276
>
> So, Anselm said:
>
> Sorry for the delayed answer, here is the use case.
>
> I tried to write a context manager that changes the execution host of
> the body. In|__enter__|I pickle the tasklet and transfer the pickle to
> another process and unpickle it there. Then the tasklet executes until
> it calls|__exit__|. In exit I pickle it again and transfer it back to
> the original process.
>
> This is really interesting. How did it pan out? Also, How does it work
> on the originating site? A context manager does not (currently) allow
> the body code to be skipped, which I presume is what must happen on the
> “source” side. (although, this here patch
> <http://bugs.python.org/issue18677> would allow that)
>
> I’m very much a fan of context managers these days. I just added
> stackless.atomic(), a built-in to provide performance for this
> ubiquitous thing.
>
>
>
> _______________________________________________
> Stackless mailing list
> [email protected]
> http://www.stackless.com/mailman/listinfo/stackless
>
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