October 2004 - Zope - Zope lists

RE: [Zope] How to handle ZODB conflict errors
by Sean Hastings 15 Nov '04

15 Nov '04

The slowdowns result when various transactions are trying to modify the same data. When a conflict happens, one of the transactions is rolled back and attempted again from the beginning. If the transaction takes a long time to execute, and this happens many times, the delays can be considerable. Only after some number of attempts, with continuing conflicts occurring, will the transaction give up and allow the Conflict Error to actually be raised back to the level of producing an error page, but each one will be logged in your event.log file. I wrote the following to explain conflicts to my own satisfaction: ------------------------------------------------------------------- There are two types of conflict errors: Read Conflict: -------------- Transaction 1 reads object A. Transaction 2 modifies object B. Transaction 1 attempts to read object B, but notices that object B has been modified since Transaction 1 began to read data. Since the data it read from A, and the data that it now finds in B are not necessarily consistent, a Read Conflict Error is produced. Transaction 1 rolls back and restarts. Write Conflict: --------------- Transaction 1 reads object A. Transaction 2 modifies object A. Transaction 1 attempts to modify object A, but notices that object A has been modified since it was read. Since overwriting the changes made by Transaction 2 would cause "lost update problems" and possible data inconsistency, a Write Conflict Error is produced. If conflict is not handled (see below), Transaction 1 rolls back and restarts. Solutions: --------- Read Conflicts - If you do not care about consistency during your read, you can execute the statement "get_transaction().commit()" after each new object accessed. This breaks your transactions up into smaller transactions that are MUCH less likely to cause conflicts. I understand that Zope 2.8 (alpha any day now) will eliminate Read Conflicts by including the ability to read old constant states. In the example above, Transaction 1 would then just read the old state of B before Transaction 2 had modified it. Write Conflicts - You can define a method on any ZODB object called "_p_resolveConflict". When a write conflict occurs, the first thing that happens is that Zope tries to call this method to handle the problem, passing it all the possible states of the object: OLD, FOUND, and TRIED. OLD is the state that the transaction first read. FOUND is the new modified state that some other transaction saved the object as. TRIED is the state that the transaction wanted to save the object as when it realized that there was a conflict. This method is intended to return a merged version of the two objects. If you do not care about lost updates, this method could be as simple as: def _p_resolveConflict(self,old,found,tried): return tried ------------------------------------------------------------------- Here is an example of some code that I think works to handle write conflicts in an order independent list. The object in question is a ZODB wrapper for a list. The [] is stored in the "data" element referred to in saved.data, old.data, etc: def _p_resolveConflict(self,old,saved,new): """ Merges two possible list states Accounts only for additions and deletions, not changes of order Prevents duplicate add or remove of same Item during conflict """ #get changes made in saved state saved_added = [] saved_removed = [] for item in saved.data: for i in range(saved.count(item) - old.count(item)): saved_added.append(item) for item in old.data: for i in range(old.count(item) - saved.count(item)): saved_removed.append(item) #get changes made in new state new_added = [] new_removed = [] for item in new.data: for i in range(new.count(item) - old.count(item)): saved_added.append(item) for item in old.data: for i in range(old.count(item) - new.count(item)): new_removed.append(item) #get duplicate changes both_added=[] for item in new_added: if saved_added.count(item): both_added.append(item) new_added.remove(item) saved_added.remove(item) both_removed=[] for item in new_removed: if saved_removed.count(item): both_removed.append(item) new_removed.remove(item) saved_removed.remove(item) #apply changes old.extend(saved_added) old.extend(new_added) old.extend(both_added) for item in saved_removed: old.remove(item) for item in new_removed: old.remove(item) for item in both_removed: old.remove(item) return old

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adding properties trough pythonscript
by rv000299 09 Nov '04

09 Nov '04

Hi all, I have some problems adding properties trough a python script def publishcontainer(container,path): ov=map(lambda x:(x.id,x), container.objectValues()) ov.sort() for (oid,obj) in ov: if not (hasattr(obj,"isPortalContent") or obj.isPrincipiaFolderish): continue id="" if hasattr(obj,"isPortalContent"): print "ID: ",path+"/"+str(obj.id) try: context.manage_addProperty('prop', 0, 'boolean') print "prop added<br>" except: print "adding prop to",str(obj.id),"failed<br>" if hasattr(obj,"objectValues"): print publishcontainer(obj,path+"/"+str(obj.id)) return printed The problem is not getting the property added, it does, but editing it afterwards in the ZMI is impossible. When I hit the Properties tab of the item, the newly added property is not on the page. However when I call the prop with a dtml-var it is rendered. I'm at a loss here. Can someone help me out? Roel ----------------------------------------------------- Make cheaper and longer calls thanks to Scarlet Phone More info at http://www.scarlet.be/nl/consumer/phone/

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2.7.3 -> 2.8 Problems
by Rakotomandimby Mihamina 05 Nov '04

05 Nov '04

Hello, I'm running Zope on my personnal websites about 200~500 uniques visits/day (according to FSCounter) I try to help the developpement by using the very latest version each time i can. I'm running Debian Testing on an x86 : I compiled with gcc version 3.3.4 Python 2.3.4 Now i'm passing from 2.7.3 to 2.8 alpha1 . The site is a Plone one (Plone 2.0.4) And there is a VHM to the plone site. www.rktmb.org/site_principal (site_principal is the ID of the plone site) I get this error when requesting the site www.rktmb.org [...] Module ZPublisher.Publish, line 187, in publish_module_standard * Module Products.PlacelessTranslationService.PatchStringIO, line 51, in new_publish * Module ZPublisher.Publish, line 144, in publish * Module Zope.App.startup, line 205, in zpublisher_exception_hook * Module ZPublisher.Publish, line 113, in publish * Module ZPublisher.mapply, line 88, in mapply * Module ZPublisher.Publish, line 40, in call_object * Module Products.CMFCore.PortalContent, line 116, in __call__ * Module Shared.DC.Scripts.Bindings, line 306, in __call__ * Module Shared.DC.Scripts.Bindings, line 343, in _bindAndExec * Module Products.CMFCore.FSPageTemplate, line 191, in _exec * Module Products.CMFCore.FSPageTemplate, line 124, in pt_render * Module Products.PageTemplates.PageTemplate, line 96, in pt_render <FSPageTemplate at /site_principal/document_view used for /site_principal/index_html> TypeError: unbound method pt_getContext() must be called with ZopePageTemplate instance as first argument (got nothing instead) (Also, an error occurred while attempting to render the standard error message.) -- ASPO Infogérance http://aspo.rktmb.org/activites/infogerance Unofficial FAQ fcolc http://faq.fcolc.eu.org/ LUG sur Orléans et alentours. Tél : 02 38 76 43 65 (France)

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change user password
by Eddy Ilg 04 Nov '04

04 Nov '04

Hi, another question that zope.org could not answer: How can I implement a own interface to change the user password? (Standard Zope acl user) Eddy

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[ANN] HTMLDocument 1.0 released
by Maik Jablonski 03 Nov '04

03 Nov '04

Hi, for all people who are (mis;))-using the Zope Mangement Interface (ZMI) as small, but very powerful, flexible and rock-stable Content-Management-System, I've just released HTMLDocument 1.0 (which I use for several years now). HTMLDocument supports WYSIWYG-editing of HTML-content with Epoz (http://mjablonski.zope.de/Epoz) and renders its content (just the body of an edited or uploaded HTML-page) automagically with the famous combination of standard_html_header / standard_html_footer (DTML) or a single standard_html_template (ZPT). So all your content can be seperated from any template-logic and you'll setup an easy-to-use-and-very-flexible CMS-solution based on the ZMI within minutes. Create a template for your site, create a folder (for seperating your content from templates and other scripts), create some HTMLDocuments in this folder, click view and you're online...:) HTMLDocument is a simple solution for all people who don't need or want a big suite like Plone / CPS or want a stable (and easy to upgrade) basement for their content: HTMLDocument should work out of the box as long as Zope supports the builtin DTMLDocument on which HTMLDocument is based. "Download":http://mjablonski.zope.de/HTMLDocument Keep zoped, Maik

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Number of Zope process on Linux
by Ulrich Wisser 02 Nov '04

02 Nov '04

Hi, I am running Zope on Linux (RH 9). Performance is not that great (to say the least). I can see only two Zope processes and only one seems to use any cpu time. Is that supposed to be like that? Should I do anything about it? If so, what do I need to do? I realize that this has been discussed before, I just couldn't find the thread in the archives or through Google. TIA Ulrich

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Zope Book?
by Shane Graber 01 Nov '04

01 Nov '04

I'm slowly learning Zope and have read through the Zope Book 2.6 that's available from zope.org. I am also interested in purchasing an additional book to better understand using Zope. Does anyone have any recommendations? I've been using Zope for a couple months now (primarily for Plone). I'm fairly low on the learning curve and would like to find a good overall book on the subject. Does anyone have any recommendations? Thanks in advance, Shane Graber

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[ANNOUNCE] VarImage 2.4 released
by Terry Hancock 31 Oct '04

31 Oct '04

VarImage 2.4.0 Released! "VarImage" or "Variable Image" is a dynamic image manipulation product for Zope which allows images to be resized, filtered, and otherwise manipulated by a simple URL syntax, using a set of plugin "operators" which can be chained. Example: MyImage/th_500_200.bw.jpg With stock VarImage, this thumbnails the image to 500x200*, converts to black and white, and converts to JPEG format for publication. *This is the "foveal thumbnail" which crops as needed to acheive the desired aspect ratio while maximally preserving the "foveal region" of the image, which you can edit from the Zope Management page of VarImage objects. VarImage is a sub-project of the "Narya Project Incubator and Forum" project http://sourceforge.net/projects/narya-project http://narya.net and is distributable under the Gnu Public License. RELEASE 2.4: This is a much more polished version of VarImage, owing to a three-month stint without internet access (and therefore nothing to do on the computer but hack. ;-)). The only minus is that VarImage probably now requires Python 2.3 / Zope 2.7.0 now (but you were gonna upgrade by now anyway, right?). I say "probably" because I simply haven't tested it with earlier versions. Highlights: * Changed plugin profile to include an explicit "caller" reference (just like the "self" in Python object methods). This really simplifies writing plugins which need to access image properties (e.g. it could use information in a caption to control a plugin's behavior). * Referer blocking REALLY works now. Furthermore, there are several popular REFERER policies that are very easy to use VarImage for now. * Configuration files using .cfg format. * Security against DoS style attacks: it is now possible to set various kinds of limits on operator chaining and argument dimensions to avoid abusive demands on your server. (I've never heard of VarImage actually being exploited this way, but the possibility has been suggested, and these limits attempt to address that threat). SOURCEFORGE RELEASES PAGE: http://sourceforge.net/project/showfiles.php?group_id=99506 FULL RELEASE NOTES and CHANGELOG: http://sourceforge.net/project/shownotes.php?release_id=277890 ACTUAL DOWNLOAD SITE: http://prdownloads.sourceforge.net/narya-project/VarImage-2.4.0.tgz?download Thanks for your interest in VarImage, I hope you find it useful. Terry Hancock -- Terry Hancock ( hancock at anansispaceworks.com ) Anansi Spaceworks http://www.anansispaceworks.com

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Zope and IIS6
by Garito 31 Oct '04

31 Oct '04

Hi all! I try to configure a Zope behind an IIS6 using hiperlogica error404 script but the script seems to be erroneous in one aspect If I try to view a Zope page it works fine The problems begin when I need to send POST data The Zope don't recive any form variable Did you solve the issue? Can you help me, please? Thanks a lot!

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Zope based Webmail app
by John Poltorak 30 Oct '04

30 Oct '04

Is such a thing as a Zope based Web mail application available? -- John

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