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<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Carol,<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>As a quick fix, we have created a stand
alone program that does the database access.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>So from the python external method (zope) that
retrieves data, instead of making the connections to the DB directly it now
calls os.popen(“python getdata.py”).<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>This forces the launch of a separate python
interpreter for the duration of the query.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Unfortunately, we will suffer the overhead
of doing this for each DB call, but that is far better than denying service to
all other sessions.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>We are already in the process of moving to
MySQL for our databases, and the MySQL adapter does not appear to exhibit this
behavior.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Jon Emmons<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
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<p class=MsoNormal><b><font size=2 face=Tahoma><span style='font-size:10.0pt;
font-family:Tahoma;font-weight:bold'>From:</span></font></b><font size=2
face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma'> Carol Ludwig
[mailto:csl@med.unc.edu] <br>
<b><span style='font-weight:bold'>Sent:</span></b> Wednesday, June 04, 2008
10:58 AM<br>
<b><span style='font-weight:bold'>To:</span></b> Jon Emmons<br>
<b><span style='font-weight:bold'>Cc:</span></b> 'Dieter Maurer'; zope@zope.org<br>
<b><span style='font-weight:bold'>Subject:</span></b> Re: RE: [Zope]
Multithreading sessions</span></font><o:p></o:p></p>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>We are using Plone and Zope against a legacy Ingres database, and I
found a similar problem<br>
using the adapter provided. I found that the C library modules (open
source) actually contained<br>
calls to make the adapter work as we wanted, much like our other web interfaces
which maintain<br>
the db and user permissions info as a "connection", but close the
actual query after each. I had<br>
to modify the Python Zope product to set "autocommit" and call the
desired close in order to get <br>
the behaviour we were looking for -- keeping the connection, but releasing each
session so that<br>
the DB backend does not register an active session between actual
queries.<br>
<br>
That's open source. Code terminology for "re-write it".<br>
<br>
----- Original Message -----<br>
From: Jon Emmons <jon.emmons@earthwavetech.com><br>
Date: Wednesday, June 4, 2008 8:50<br>
Subject: RE: [Zope] Multithreading sessions<br>
To: 'Dieter Maurer' <dieter@handshake.de><br>
Cc: zope@zope.org<br>
<br>
> Dieter,<br>
> <br>
> Thanks for this input. Your comments here turned out to be <br>
> dead on. The<br>
> problem is the GIL.<br>
> <br>
> We are currently running Sybase databases using the python <br>
> Sybase-0.37<br>
> module for data access.<br>
> <br>
> This module will set the GIL. So if the query takes any <br>
> time at all, every<br>
> other session will freeze. It does release it when the <br>
> connection is<br>
> closed, but if the query takes awhile it effectively denies <br>
> service to every<br>
> other session.<br>
> <br>
> I am just learning about this, but my initial inquiries suggest <br>
> that the<br>
> only way to achieve true concurrency using a language like <br>
> python is to<br>
> launch multiple interpreters.<br>
> <br>
> I don't yet have the solution to my problem, but at least now I <br>
> know what<br>
> the problem is, and that is half the battle.<br>
> <br>
> Thanks again, and thanks to everyone's input, it has helped immensely.<br>
> <br>
> Jon Emmons<br>
> <br>
> -----Original Message-----<br>
> From: Dieter Maurer [mailto:dieter@handshake.de] <br>
> Sent: Wednesday, May 28, 2008 2:27 PM<br>
> To: Jon Emmons<br>
> Cc: zope@zope.org<br>
> Subject: Re: [Zope] Multithreading sessions<br>
> <br>
> Jon Emmons wrote at 2008-5-23 08:58 -0400:<br>
> > ...<br>
> >I am running zope 2.9.4 and have observed that it will not <br>
> simultaneously>serve pages to my users.<br>
> <br>
> Usually, it does.<br>
> <br>
> I have seen database adapter packages (an old "psycopg" version,
<br>
> to be<br>
> precise) that forgot to release the GIL for some operations.<br>
> Then Zope freezes while these operations are executed.<br>
> <br>
> <br>
> A surprising report of a similar kind was: while Zope's embedded<br>
> profiler is in use, Zope effectively runs in single thread mode (such<br>
> that other threads do not distort the timing results).<br>
> Probably not your problem ... but who knows.<br>
> <br>
> <br>
> Further potential reasons (for almost surely not responsible for your<br>
> current problem:<br>
> <br>
> Expensive operations implemented in "C" (such as <br>
> operations on huge<br>
> strings)<br>
> <br>
> Creating excessive amounts of objects (causing lots<br>
> of generation 2 garbage collections which hold the GIL)<br>
> <br>
> <br>
> <br>
> -- <br>
> Dieter<br>
> <br>
> _______________________________________________<br>
> Zope maillist - Zope@zope.org<br>
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> <o:p></o:p></span></font></p>
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