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 It may be out of date.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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