[web2py] Re: How to do it: Handling import path manipulation + GAE + deferred?

[howesc]

Constantine,

perhaps because i was not able to untangle the deferred library and paths 
and how to get GAE and web2py to play nice together (i remember it was a 
long afternoon a couple of years ago and that is about all), i found 
http://code.google.com/appengine/docs/python/taskqueue/functions.html which 
allows me to add a request to the taskqueue.

now, this is different then deferred.  i believe deferred is like running a 
python script/module sometime in the future, whereas the taskqueue is like 
scheduling a curl request to your server sometime in the future.  once i 
wrapped my head around that and wrapped my script/module into a web2py 
controller function i was up and running in minutes.

that said, have you looked into using taskqueue?  what does deferred have 
that taskqueue does not?  perhaps i missed something by giving up on 
deferred.

christian

[web2py] Re: How to do it: Handling import path manipulation + GAE + deferred?

[Constantine Vasil]

Thank you, I know about it but I am using deferred because I have a lot of 
tasks ad-hoc from a functions. Using deferred eliminates the need to create 
a separate url for each task.

[web2py] Re: How to do it: Handling import path manipulation + GAE + deferred?

[Alan Etkin]

I went in a similar problem with an webapp that needs to add routes to
the Python path.
I didn't need a special module. Just made the path adjustments in the
app's specific routes.py module that executes once when web2py starts.
Doing path modifications is troublesome (something to do with
threading)

Look here
http://groups.google.com/group/web2py/browse_thread/thread/607e9c384ec220e0/2199c108556060e7

I belive GAE does not support the use of os and sys. Check for updates
on the subject.

On 6 dic, 15:03, Constantine Vasil thst...@gmail.com wrote:
 I am using deferred library with GAE. In order to do that I have to define
 a
  'fix_path' module and import the 'fix_path' in the module  deferred.defer.

 What I need to do in order deferred to work with web2py?

 Regards,
 --Constantine

 http://code.google.com/appengine/articles/deferred.html
 Handling import path manipulation

 Some applications, or the frameworks they use, rely on manipulating the
 Python import path in order to make all the libraries they need available.
 While this is a perfectly legitimate technique, the deferred library has no
 way of knowing what path manipulations you've engaged in, so if the task
 you're deferring relies on modules that aren't on the import path by
 default, you need to give it a helping hand. Failing to do this can result
 in your tasks failing to run - or worse, only failing intermittently.

 Fortunately, handling this is easy. Make sure your code that changes the
 import path is in a module all of its own, such as 'fix_path.py'. Such a
 module might look like this:

 import os
 import sys

 sys.path.append(os.path.join(os.path.dirname(__file__), 'lib'))

 Then, import the 'fix_path' module along with your usual imports, anywhere
 you rely on the modified path, such as in the module you defined the
 functions you're calling with deferred.defer in.

[web2py] Re: How to do it: Handling import path manipulation + GAE + deferred?

[Constantine Vasil]

Yes I know about path modifications but anything web2py related - 
I am listening to web2py experts ;) 

This thing is - deferred is very important functionality and we need this.

Probably Massimo will know the answer?

[web2py] Re: How to do it: Handling import path manipulation + GAE + deferred?

[Constantine Vasil]

Google says:
if the task you're deferring* relies on modules* that aren't on the import 
path by default, you need to give it a 
helping hand.

path modifications: in your link:
you should not change sys.path when you have more than one thread running.

The Google example:
sys.path.*append*(os.path.join(os.path.dirname(__file__), 'lib'))

Is not changing sys.path, but appending to it.