[Zope] How to create an ansynchronous method

[Chris Withers]

Hi David,

Just a note in passing to say that what you're really after in this case 
is Gary Poster's ZASync. Gary's talked to me about getting Stepper 
(which is basically batch processing triggered via cron using a ZEO 
connection) to do the work of processing ZAsync's queue, which would be 
cool, but I don't know if either of us has the need/time to make that 
happen...

cheers,

Chris

gary's talked with me about doing the

David Pratt wrote:
> Hi Ron.  I found the following trying to follow up a bit on what you 
> have suggested. I believe it is similar to what you are doing from your 
> explanation.  It may be out of date.   I have not attempted to daemonize 
> a process to date so it  would be great if you could look at this and 
> comment since I need something to work with.
> 
> http://mail.python.org/pipermail/python-list/2001-February/030814.html
> 
> As far as interacting with Zope, I have done something similar to build 
> a site remotely from another server but setup https and sent credentials 
> in the urls.  I wonder if there is a way to inject them into Zope 
> another way since the daemon is on the machine.  I think the ClockServer 
> injects requests into Zope.  I believe it is something similar since 
> credentials still need to be in url to execute something but requests 
> are not exposed to the web doing this.
> 
> Regards,
> David
> 
> On Wednesday, September 14, 2005, at 12:11 AM, Ron Bickers wrote:
> 
>> On Tue September 13 2005 08:16 pm, David Pratt wrote:
>>
>>> How is it that you send a signal to the long running
>>> process?
>>
>>
>> The long-running process writes a pid file and waits for a SIGUSR1 signal
>> (using Python's signal module).  A small External Method, called when the
>> user submits the form, reads the pid file and sends the signal to the
>> process.
>>
>>> Is the long running process cronned to look for a record in
>>> the database or is this starting another server of some type.
>>
>>
>> It waits for a SIGUSR1 signal from the website, otherwise it's idle.  
>> That
>> way it can begin processing immediately but doesn't have to do any 
>> periodic
>> checking.  I do, however, have a cron job that starts it every 15 
>> minutes in
>> case it dies.  The process knows if it's already running, so it's safe to
>> just start it regularly.
>>
>>> What I need is something like what you are suggesting - wakes up when
>>> there is work in the hopper and chugs along until it is done and then
>>> goes to sleep (sort of the way a printing queue works). At the same
>>> time it would be great if it was something that had a small RAM
>>> footprint or ran without consuming any more than X mbs.
>>
>>
>> The part that waits for the signal is very small, but it loads the 
>> Reportlab
>> modules and reads a bunch of data to do the work, so it can get large at
>> times.  If it were to just call an external program that dies after doing
>> its work, you could easily keep memory usage low.
>>
>>> The other
>>> problem I have with this is that it needs to do work in Zope itself
>>> since the final docs end up as objects.  I have just found Chris
>>> Wither's product called Stepper. I am not sure it this is for this type
>>> of situation or more for cronned maintenance.
>>
>>
>> I have no idea.  Maybe it'll do what you want, but I don't understand 
>> what it
>> really does just from the description.  The work I needed to do was 
>> external
>> to Zope anyway (reading data from a MySQL database, building PDFs with
>> Reportlab, sending email), so it's actually better that I'm outside of 
>> it.
>>
>> When I have to run things in Zope from outside, I run curl with a URL 
>> of a
>> Python Script that does the work.  It's a hack, but I've never had a 
>> problem
>> with it.  I'm not sure how else you would work in Zope from a process
>> outside of Zope.
>>
>> -- 
>> Ron
>>
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