blog entries created by Sylvain Thenault
show 24 results
  • Summer CubicWeb/Narval Sprint - Final report

    2010/08/18 by Sylvain Thenault

    For that last sprint day, each team made some nice achievements:

    • Steph & Alain worked on the mv/cp actions implementation to makes them working properly and supporting globs. Last but not least, with a full set of tests.
    • Alex & Charles got back what we call apycot 'full' tests, eg running test with coverage enabled, checking that code coverage is greater than a given threshold, but also running pylint and checking that its global evaluation is at least 7 (configurable, of course).
    • Katia & Aurélien provided a sharp implementation of recipe checking, so that we know we don't launch a recipe badly constructed, as well as informing the user nicely from what errors his recipe suffer.
    • Julien managed to set up a recipe managing from Debian package construction to Debian repository publication, going through lintian on the way
    • Pierre-Yves helped other teams to solve the narval related bugs they encountered, and finished by writing a thread-safe implementation of apycot's writer so we can run several checker simultaneously.
    • Celso continued working on a proof of concept blue-theme cube, wondering how to make CubicWeb looks nicer and be easily customisable in future versions.
    • Sylvain helped there and there and integrated patches...

    So we finally didn't get up to the demo. But we now have everything to set it up, so I've a good hope that we will have a beta version of our brand new production chain up and running before the end of August!

    Thanks to everyone for all this good work, and for this time spent all together!


  • Summer CubicWeb/Narval Sprint - Day 1

    2010/08/10 by Sylvain Thenault

    We started this first day by several presentations by Sylvain about Logilab's current development process workflow, and compared it to what it should be after the sprint. Sylvain also introduced Narval.

    We then set up a dev environment on everyone's computer: a working forge with a local Narval agent that can be used for tests during the week.

    Regarding more concrete tasks:

    • Charles and Alexandre started writing some basic Narval actions such as move, to move a file from a place to another, and had to grasp narval's concepts on the way.
    • Pierre-Yves dug into the code to understand how exceptions are propagated in the Narval engine, his goal was to get better reports.
    • Stéphanie and Alain worked on a nice bot status view.
    • Katia, Aurélien studied the new mercurial cache solution for vcsfile
    • Julien started some piece of documentation.
    • Celso, our Mexican friend, discovered some new features of recent cubicweb releases and setup his environment to later work on Spanish translation, CSS, etc.
    • Sylvain came with a basically working narval implementation on top of cubicweb, and spent the day helping various people...

  • Summer CubicWeb/Narval Sprint

    2010/08/10 by Sylvain Thenault

    Although this week is normally the regular annual holidays here at Logilab, some of us will sprint in Paris exceptionally.

    Focus

    We're starting this week with an exciting goal: integrating all our release process into our continuous integration suite (through the apycot cube). Including Debian repository management, pypi registration, etc...

    The hot stuff to achieve this is the third resurrection of Narval, the project Logilab was originaly based on, but this time it is built on top of CubicWeb framework. Narval will be used to rewrite some parts of apycot, in order to make it more flexible and powerful.

    It is not just a refactoring or a simple upgrade! We hope to automate common tasks, simplify maintenance, and thus enhance release quality, but also gain a lot of functionality in near future.

    Sprint roadmap

    • merge Apycotbot process manager into a new Narval incarnation, and rewrite it as Narval actions and recipes
    • improve vcsfile cube with a new cache system for mercurial
    • define Logilab's release process as new Narval recipes, triggered by actions such as adding release tag into the source repository

    More detailed stuff will come with the sprint reports that we'll try to issue each day.

    Information

    This sprint is taking place in Logilab's offices in Paris from Monday the 9th to the 13th of August 2010.


  • Building my photos web site with CubicWeb part IV: let's make it more user friendly

    2010/07/13 by Sylvain Thenault

    Step 0: updating code to CubicWeb 3.9 / cubicweb-file 1.9

    CubicWeb 3.9 brings several improvements that we'll want to use, and the 1.9 version of the file cube has a major change: the Image type has been dropped in favor of an IImage adapter that makes code globally much cleaner (although this is not directly visible here). So the first thing to do is to upgrade our cube to the 3.9 API. As CubicWeb releases are mostly backward compatible, this is not mandatory but it's easier to follow changes as they come than having a huge upgrade to do at some point. Also, this remove deprecation warnings which are a bit tedious...

    Since we only have very few lines of code, this step is pretty simple. Actually the main thing we have to do is to upgrade our schema, to remove occurrences of the Image type or replace them by the File type. Here is the (striped) diff:

     class comments(RelationDefinition):
         subject = 'Comment'
    -    object = ('File', 'Image')
    +    object = 'File'
         cardinality = '1*'
         composite = 'object'
    
     class tags(RelationDefinition):
         subject = 'Tag'
    -    object = ('File', 'Image')
    +    object = 'File'
    
     class displayed_on(RelationDefinition):
         subject = 'Person'
    -    object = 'Image'
    +    object = 'File'
    
     class situated_in(RelationDefinition):
    -    subject = 'Image'
    +    subject = 'File'
         object = 'Zone'
    
     class filed_under(RelationDefinition):
    -    subject = ('File', 'Image')
    +    subject = 'File'
         object = 'Folder'
    
     class visibility(RelationDefinition):
    -    subject = ('Folder', 'File', 'Image', 'Comment')
    +    subject = ('Folder', 'File', 'Comment')
         object = 'String'
         constraints = [StaticVocabularyConstraint(('public', 'authenticated',
                                                    'restricted', 'parent'))]
    
     class may_be_readen_by(RelationDefinition):
    -    subject = ('Folder', 'File', 'Image', 'Comment',)
    +    subject = ('Folder', 'File', 'Comment',)
         object = 'CWUser'
    
    
    -from cubes.file.schema import File, Image
    +from cubes.file.schema import File
    
     File.__permissions__ = VISIBILITY_PERMISSIONS
    -Image.__permissions__ = VISIBILITY_PERMISSIONS
    

    Now, let's set the dependency in the __pkginfo__ file. As 3.8 simplifies this file, we can merge __depends_cubes__ (as introduced in the first blog of this series) with __depends__ to get the following result:

    __depends__ = {'cubicweb': '>= 3.9.0',
                   'cubicweb-file': '>= 1.9.0',
                   'cubicweb-folder': None,
                   'cubicweb-person': None,
                   'cubicweb-zone': None,
                   'cubicweb-comment': None,
                   'cubicweb-tag': None,
                   }
    

    If your cube is packaged for debian, it's a good idea to update the debian/control file at the same time, so you won't forget it.

    That's it for the API update, CubicWeb and cubicweb-file will handle other stuff for us. Easy, no?

    We can now start some more fun stuff...

    Step 1: let's improve site's usability for our visitors

    The first thing I've noticed is that people to whom I send links to photos with some login/password authentication get lost, because they don't grasp they have to login by clicking on the 'authenticate' link. That's probably because they only get a 404 when trying to access an unauthorized folder, and the site doesn't make clear that 1. you're not authenticated, 2. you could get more content by authenticating yourself.

    So, to improve this situation, I decided that I should:

    • make a login box appears for anonymous, so they see at a first glance a place to put the login / password information I provided
    • customize the 404 page, proposing to login to anonymous.

    Here is the code, samples from my cube's views.py file:

    from cubicweb.selectors import is_instance
    from cubicweb.web import box
    from cubicweb.web.views import basetemplates, error
    
    class FourOhFour(error.FourOhFour):
        __select__ = error.FourOhFour.__select__ & anonymous_user()
    
        def call(self):
            self.w(u"<h1>%s</h1>" % self._cw._('this resource does not exist'))
            self.w(u"<p>%s</p>" % self._cw._('have you tried to login?'))
    
    class LoginBox(box.BoxTemplate, basetemplates.LogFormView):
        """display a box containing links to all startup views"""
        __regid__ = 'sytweb.loginbox'
        __select__ = box.BoxTemplate.__select__ & anonymous_user()
    
        title = _('Authenticate yourself')
        order = 70
    
        def call(self, **kwargs):
            self.w(u'<div class="sideBoxTitle"><span>%s</span></div>' % self.title)
            self.w(u'<div class="sideBox"><div class="sideBoxBody">')
            self.login_form('loginBox')
            self.w(u'</div></div>')
    

    The first class provides a new specific implementation of the default page you get on a 404 error, to display an explicit message for anonymous users.

    Note

    Thanks to the selection mechanism, it will be selected for anonymous users, since the additional anonymous_user() selector gives it a higher score than the default, and not for authenticated since this selector will return 0 otherwise (hence the object won't be selectable).

    The second class defines a simple box, that will be displayed by default with boxes in the left column, thanks to default box.BoxTemplate'selector. The HTML is written to match default CubicWeb boxes style. To get the actual login form, we inherit from the LogFormView view which provides a login_form method (handling some stuff under the cover for us, hence the multiple inheritance), that we simply have to call to get the form's HTML.

    login box / 404 screenshot

    The login box and the custom 404 page for an anonymous visitor (translated in french)

    Step 2: providing a custom index page

    Another thing we can easily do to improve the site is... A nicer index page (e.g. the first page you get when accessing the web site)! The default one is quite intimidating (that should change in a near future). I will provide a much simpler index page that simply list available folders (e.g. photo albums in that site).

    from cubicweb.web.views import startup
    
    class IndexView(startup.IndexView):
        def call(self, **kwargs):
            self.w(u'<div>\n')
            if self._cw.cnx.anonymous_connection:
                self.w(u'<h4>%s</h4>\n' % self._cw._('Public Albums'))
            else:
                self.w(u'<h4>%s</h4>\n' % self._cw._('Albums for %s') % self._cw.user.login)
            self._cw.vreg['views'].select('tree', self._cw).render(w=self.w)
            self.w(u'</div>\n')
    
    def registration_callback(vreg):
        vreg.register_all(globals().values(), __name__, (IndexView,))
        vreg.register_and_replace(IndexView, startup.IndexView)
    

    As you can see, we override the default index view found in cubicweb.web.views.startup, getting back nothing but its identifier and selector since we override the top level view's call method.

    Note

    In that case, we want our index view to replace the existing one. We implement the registration_callback function, in which we code a registeration of everything in the module but our IndexView, then we register it instead of the former index view.

    Also, we added a title that tries to make it more evident that the visitor is authenticated, or not. Hopefully people will get it now!

    default index page screenshot

    The default index page

    new index page screenshot

    Our simpler, less intimidating, index page (still translated in french)

    Step 3: more navigation improvements

    There are still a few problems I want to solve...

    • Images in a folder are displayed in a somewhat random order. I would like to have them ordered by file's name (which will usually, inside a given folder, also result ordering photo by their date and time)
    • When clicking a photo from an album view, you've to get back to the gallery view to go to the next photo. This is pretty annoying...
    • Also, when viewing an image, there is no clue about the folder to which this image belongs to.

    I will first try to explain the ordering problem. By default, when accessing related entities by using the ORM's API, you should get them ordered according to the target's class fetch_order. If we take a look at the file cube's schema, we can see:

    class File(AnyEntity):
        """customized class for File entities"""
        __regid__ = 'File'
        fetch_attrs, fetch_order = fetch_config(['data_name', 'title'])
    

    By default, fetch_config will return a fetch_order method that will order on the first attribute in the list. We could expect to get files ordered by their name. But we don't. What's up doc ?

    The problem is that files are related to folder using the filed_under relation. And that relation is ambiguous, eg it can lead to File entities, but also to Folder entities. In such a case, since both entity types don't share the attribute on which we want to sort, we'll get linked entities sorted on a common attribute (usually modification_date).

    To fix this, we have to help the ORM. We'll do this in the method from the ITree folder's adapter, used in the folder's primary view to display the folder's content. Here's the code that I've put in our cube's entities.py file, since it's more logical stuff than view stuff:

    from cubes.folder import entities as folder
    
    class FolderITreeAdapter(folder.FolderITreeAdapter):
    
        def different_type_children(self, entities=True):
            rql = self.entity.cw_related_rql(self.tree_relation,
                                             self.parent_role, ('File',))
            rset = self._cw.execute(rql, {'x': self.entity.eid})
            if entities:
                return list(rset.entities())
            return rset
    
    def registration_callback(vreg):
        vreg.register_and_replace(FolderITreeAdapter, folder.FolderITreeAdapter)
    

    As you can see, we simply inherit from the adapter defined in the folder cube, then we override the different_type_children method to give a clue to the ORM's cw_related_rql method, that will generate the rql to get entities related to the folder by the filed_under relation (the value of the tree_relation attribute). The clue is that we only want to consider the File target entity type. By doing this, we remove the ambiguity and get back a RQL query that correctly orders files by their data_name attribute.

    Note

    • Adapters have been introduced in CubicWeb 3.9 / cubicweb-folder 1.8.
    • As seen earlier, we want to replace the folder's ITree adapter by our implementation, hence the custom registration_callback method.

    Ouf. That one was tricky...

    Now the easier parts. Let's start by adding some links on the file's primary view to see the previous / next image in the same folder. CubicWeb provides a component that do exactly that. To make it appear, it has to be adaptable to the IPrevNext interface. Here is the related code sample, extracted from our cube's views.py file:

    from cubicweb.selectors import is_instance
    from cubicweb.web.views import navigation
    
    
    class FileIPrevNextAdapter(navigation.IPrevNextAdapter):
        __select__ = is_instance('File')
    
        def previous_entity(self):
            rset = self._cw.execute('File F ORDERBY FDN DESC LIMIT 1 WHERE '
                                    'X filed_under FOLDER, F filed_under FOLDER, '
                                    'F data_name FDN, X data_name > FDN, X eid %(x)s',
                                    {'x': self.entity.eid})
            if rset:
                return rset.get_entity(0, 0)
    
        def next_entity(self):
            rset = self._cw.execute('File F ORDERBY FDN ASC LIMIT 1 WHERE '
                                    'X filed_under FOLDER, F filed_under FOLDER, '
                                    'F data_name FDN, X data_name < FDN, X eid %(x)s',
                                    {'x': self.entity.eid})
            if rset:
                return rset.get_entity(0, 0)
    

    The IPrevNext interface implemented by the adapter simply consist of the previous_entity / next_entity methods, that should respectively return the previous / next entity or None. We make an RQL query to get files in the same folder, ordered similarly (eg by their data_name attribute). We set ascendant/descendant ordering and a strict comparison with current file's name (the "X" variable representing the current file).

    Note

    • Former implements selector should be replaced by is_instance or adaptable selector with CubicWeb >= 3.9. In our case, is_instance is used to tell our adapter to get File entities.

    Notice that this query supposes we wont have two files of the same name in the same folder. Fixing this is out of the scope of this blog. And as I would like to have at some point a smarter, context sensitive previous/next entity, I'll probably never fix this query (though if I had to, I would probably choose to add a constraint in the schema so that we can't add two files of the same name in a folder).

    One more thing: by default, the component will be displayed below the content zone (the one with the white background). You can change this in the site's properties through the ui, but you can also change the default value in the code by modifying the context attribute of the component:

    navigation.NextPrevNavigationComponent.context = 'navcontentbottom'
    

    Note

    context may be one of 'navtop', 'navbottom', 'navcontenttop' or 'navcontentbottom'; the first two being outside the main content zone, the two others inside it.

    screenshot of the previous/next entity component

    The previous/next entity component, at the bottom of the main content zone.

    Now, the only remaining stuff in my todo list is to see the file's folder. I'll use the standard breadcrumb component to do so. Similarly as what we've seen before, this component is controlled by the IBreadCrumbs interface, so we'll have to provide a custom adapter for File entity, telling the a file's parent entity is its folder:

    from cubicweb.web.views import ibreadcrumbs
    
    class FileIBreadCrumbsAdapter(ibreadcrumbs.IBreadCrumbsAdapter):
        __select__ = is_instance('File')
    
        def parent_entity(self):
            if self.entity.filed_under:
                return self.entity.filed_under[0]
    

    In this case, we simply use the attribute notation provided by the ORM to get the folder in which the current file (e.g. self.entity) is located.

    Note

    The IBreadCrumbs interface is a breadcrumbs method, but the default IBreadCrumbsAdapter provides a default implementation for it that will look at the value returned by its parent_entity method. It also provides a default implementation for this method for entities adapting to the ITree interface, but as our File doesn't, we've to provide a custom adapter.

    screenshot of the breadcrumb component

    The breadcrumb component when on a file entity, now displaying parent folder.

    Step 4: preparing the release and migrating the instance

    Now that greatly enhanced our cube, it's time to release it and to upgrade production site. I'll probably detail that process later, but I currently simply transfer the new code to the server running the web site.

    However, there's some commands to get things done properly... First, as I've added some translatable string, I have to run:

    $ cubicweb-ctl i18ncube sytweb
    

    To update the cube's gettext catalogs (the '.po' files under the cube's i18n directory). Once the above command is executed, I'll then update translations.

    To see if everything is ok on my test instance, I do:

    $ cubicweb-ctl i18ninstance sytweb
    $ cubicweb-ctl start -D sytweb
    

    The first command compile i18n catalogs (e.g. generates '.mo' files) for my test instance. The second command starts it in debug mode, so I can open my browser and navigate through the web site to see if everything is ok...

    Note

    In the 'cubicweb-ctl i18ncube' command, sytweb refers to the cube, while in the two other, it refers to the instance (if you can't see the difference, reread CubicWeb's concept chapter !).

    Once I've checked it's ok, I simply have to bump the version number in the __pkginfo__ module to trigger a migration once I'll have updated the code on the production site. I can check the migration is also going fine, by first restoring a dump from the production site, then upgrading my test instance.

    To generate a dump from the production site:

    $ cubicweb-ctl db-dump sytweb
    pg_dump -Fc --username=syt --no-owner --file /home/syt/etc/cubicweb.d/sytweb/backup/tmpYIN0YI/system sytweb
    -> backup file /home/syt/etc/cubicweb.d/sytweb/backup/sytweb-2010-07-13_10-22-40.tar.gz
    

    I can now get back the dump file ('sytweb-2010-07-13_10-22-40.tar.gz') to my test machine (using scp for instance) to restore it and start migration:

    $ cubicweb-ctl db-restore sytweb sytweb-2010-07-13_10-22-40.tar.gz
    $ cubicweb-ctl upgrade sytweb
    

    You'll have to answer some questions, as we've seen in an earlier post.

    Now that everything is tested, I can transfer the new code to the production server, apt-get upgrade cubicweb 3.9 and its dependencies, and eventually upgrade the production instance.

    Conclusion

    This is a somewhat long post that starts showing you the way CubicWeb provides a highly configurable user interface, as well as powerful and reusable components. And there are a lot of others like those!

    So see you next time for part V, where we'll probably want to do more ui stuff!


  • CubicWeb 3.9 released

    2010/07/12 by Sylvain Thenault

    CubicWeb 3.9.0 went out last week. We now have tested it in production and fixed the remaining bugs, which means it is now show time!

    http://www.cubicweb.org/file/1179905?vid=download

    What's new in CubicWeb 3.9?

    The 3.9 release development was started by a one week long sprint at the beginning of May. The two goals were first to make it easier to customize the look and feel of a CubicWeb application, and second to do a big cleanup of the javascript library. This led to the following major changes.

    • We introduced property sheets, which replace former external_resources file, as well as define some constants that will be used to 'compile' cubicweb and cubes' stylesheets.
    • We started a new, clean cubicweb.css stylesheet, that tries to keep up with the rhythm. This is still a work in progress, and by default the old css is still used, unless specified otherwise in the configuration file.
    • We set the bases for web functional testing using windmill. See test cases in cubicweb/web/test/windmill/ and python wrapper in cubicweb/web/test_windmill/ if you want to use this in your own cube.
    • We set the bases for javascript unit-testing using qunit. See test cases in cubicweb/web/test/jstests/ and python wrapper in cubicweb/web/test_jscript/ if you want to use this in your own cube.
    • We cleaned the javascript code: the generic stuff moved into the cw namespace, the ajax api is now much simpler thanks to more generic and powerful functions. As usual backward compatibility was kept, which means that your existing code will still run, but you will see tons of deprecation warnings in the firebug console.
    • We implemented a simple documentation extraction system for javascript. Just put ReST in javascript comments, and get all the power of sphinx for documenting your javascript code.

    But that's not all! There are also two major changes in 3.9.

    http://www.cubicweb.org/file/1179904?vid=download

    Architectural change: adapters

    The first major change is the introduction of adapters, also found in the Zope Component Architecture and documented in the GoF book. This will allow for better application design and easier code reuse. You can see several usage in the framework, for instance the "ITree" adapter in cubicweb.entities.adapters, the "IBreadCrumbs" adapter in cubicweb.web.views.ibreadcrumbs, or still the "ICalendarable" adapter in cubicweb.web.views.calendar.

    Important full search improvement

    The second major change will benefit directly to end users: we worked with our friends from SecondWeb to expose the ranking feature found in postgres full-text search. This clearly improves the user experience when doing full-text searches. Ranking may be finely tuned by setting different weights to entity types, entity types attributes, or even be dynamically computed per entity instance. Of course, all this is done in an adapter, see "IFTIndexableAdapter" in cubicweb/entities/adapters.py.

    Minor changes

    Other minor changes include:

    • support for wildcard text search for application using postgres >= 8.4 as backend. Try searching for 'cub*' on cubicweb.org for instance.
    • inline edition of composite relation
    • nicer, clickable, schema image of the data model
    • enhanced support for the SQLserver database

    Enjoy!


  • Using RQL's HAVING clause to by-pass limitation of the WHERE clause

    2010/06/09 by Sylvain Thenault

    The HAVING clause, as in SQL, has been originally introduced to restrict a query according to value returned by an aggregat function, e.g.:

    Any X GROUPBY X WHERE X relation Y HAVING COUNT(Y) > 10
    

    It may however be used for something else...

    For instance, let's say you want to get people whose uppercased first name equals to another person uppercased first name. Since in the WHERE clause, we are limited to 3-expression (<subject> <relation> <object>), such thing can't be expressed (believe me or try it out). But this can be expressed using HAVING comparison expression:

    Person X WHERE X firstname XFN, Y firstname YFN HAVING X > Y, UPPER(XFN) = UPPER(YFN)
    

    Nice, no? This open some new possibilities. Another example:

    Person X WHERE X birthday XB HAVING YEAR(XB) = 2000
    

    Get it? That lets you use transformation functions not only in selection but for restriction as well, which was the major flaw in the RQL language.

    Notice that while we would like this to work without the HAVING clause, this can't be currently be done because it introduces an ambiguity in RQL's grammar that can't be handled by yapps, the parser's generator we're using.


  • Deactivating the 'reledit' feature

    2010/06/09 by Sylvain Thenault

    The 'reledit' feature is the one that makes attributes/relations editable in entity's primary view for authorized users (you know, the pen that appears when your mouse is over a field's value, clicking on it making a form to edit this field appears).

    This is a nice feature, but you may not want it. It can be easily deactivated everywhere it's used automatically in the site by using the code snippet below:

    from cubicweb.web.views import editforms
    
    class DeactivatedAutoClickAndEditFormView(editforms.AutoClickAndEditFormView):
        def should_edit_attribute(self, entity, rschema, form):
            return False
    
        def should_edit_relation(self, entity, rschema, role, rvid):
            return False
    
    def registration_callback(vreg):
        vreg.register_and_replace(DeactivatedAutoClickAndEditFormView,
                                  editforms.AutoClickAndEditFormView)
    

  • Building my photos web site with CubicWeb part III: storing images on the file-system

    2010/05/20 by Sylvain Thenault

    Step 1: configuring the BytesFileSystem storage

    To avoid cluttering my database, and to ease file manipulation, I don't want them to be stored in the database. I want to be able create File/Image entities for some files on the server file system, where those file will be accessed to get entities data. To do so, I've to set a custom BytesFileSystemStorage storage for the File/Image 'data' attribute, which holds the actual file's content.

    Since the function to register a custom storage needs to have a repository instance as a first argument, we have to call it in a server startup hook. So I added it in cubes/sytweb/hooks.py :

    from os import makedirs
    from os.path import join, exists
    
    from cubicweb.server import hook
    from cubicweb.server.sources import storage
    
    class ServerStartupHook(hook.Hook):
        __regid__ = 'sytweb.serverstartup'
        events = ('server_startup', 'server_maintenance')
    
        def __call__(self):
            bfssdir = join(self.repo.config.appdatahome, 'bfss')
            if not exists(bfssdir):
                makedirs(bfssdir)
                print 'created', bfssdir
            storage = storages.BytesFileSystemStorage(bfssdir)
            set_attribute_storage(self.repo, 'File', 'data', storage)
            set_attribute_storage(self.repo, 'Image', 'data', storage)
    

    Note

    • how we built the hook's registry identifier (_regid__): you can introduce 'namespaces' by using their python module like naming identifiers. This is especially important for hooks where you usually want a new custom hook, not overriding / specializing an existent one, but the concept may be used for any application objects
    • we catch two events here: "server_startup" and "server_maintenance". The first is called on regular repository startup (eg, as a server), the other for maintenance task such as shell or upgrade. In both cases, we need to have the storage set, else we'll be in trouble...
    • the path given to the storage is the place where a file added through the ui (or in the database before migration) will be located
    • be aware that by doing this, you can't write queries that will try to restrict on the File and the Image data attribute anymore. Thankfully we don't usually do that on a file's content or more generally on attributes for the Bytes type

    Now, if you've already added some photos through the web ui, you'll have to migrate existing data so that the file's content will be stored on the file-system instead of the database. There is a migration command to do so, let's run it in the cubicweb shell (in actual life, you'd have to put it in a migration script as we saw last time):

    $ cubicweb-ctl shell sytweb
     entering the migration python shell
     just type migration commands or arbitrary python code and type ENTER to execute it
     type "exit" or Ctrl-D to quit the shell and resume operation
     >>> storage_changed('File', 'data')
     [........................]
     >>> storage_changed('Image', 'data')
     [........................]
    

    That's it. Now, the files added through the web ui will have their content stored on the file-system, and you'll also be able to import files from the file-system as explained in the next part.

    Step 2: importing some data into the instance

    Hey, we're starting to have some nice features, let's give this new web site a try. For instance if I have a 'photos/201005WePyrenees' containing pictures for a particular event, I can import it to my web site by typing

    $ cubicweb-ctl fsimport -F sytweb photos/201005WePyrenees/
    ** importing directory /home/syt/photos/201005WePyrenees
      importing IMG_8314.JPG
      importing IMG_8274.JPG
      importing IMG_8286.JPG
      importing IMG_8308.JPG
      importing IMG_8304.JPG
    

    Note

    The -F option tell that folders should be mapped, hence my photos will be all under a Folder entity corresponding to the file-system folder.

    Let's take a look at the web ui:

    http://www.cubicweb.org/file/972765?vid=download

    Nothing different, I can't see the new folder... But remember our security model! By default, files are only accessible to authenticated users, and I'm looking at the site as anonymous, e.g. not authenticated. If I login, I can now see:

    http://www.cubicweb.org/file/972766?vid=download

    Yeah, it's there! You can also notice that I can see some entities as well as folders and images the anonymous users can't. It just works everywhere in the ui since it's handled at the repository level, thanks to our security model.

    Now if I click on the newly inserted folder, I can see

    http://www.cubicweb.org/file/972767?vid=download

    Great! I get my pictures in the folder. I can now give a nicer name to this folder (provided I don't intend to import from it anymore, else already imported photos will be reimported), change permissions, title for some pictures, etc... Having good content is much more difficult than having a good web site ;)

    Conclusion

    We started to see here an advanced feature of our repository: the ability to store some parts of our data-model into a custom storage, outside the database. There is currently only the BytesFileSystemStorage available, but you can expect to see more coming in a near future.

    Also, we can now start to feed our web-site with some nice pictures! The site isn't perfect (far from it actually) but it's usable, and we can start using it and improve it on the way. The Incremental Cubic Way :)

    So see you next time to start tweaking the user interface!


  • CubicWeb 3.8 released

    2010/04/28 by Sylvain Thenault

    CubicWeb 3.8.0 went out last week, but now we have tested it, produced a 3.8.1, it's show time!

    What's new in CubicWeb 3.8?

    One of the most important change is http server update to move from deadend twisted.web2 to twisted.web. With this change comes the possibility to configure the maximum size of POST request in the configuration file (was hard-coded to 100Mo before).

    Other changes include:

    • CubicWeb should now be installable through pip or easy_install. This is still experimental, and we don't use it that much so please, give us some feedback! Some cubes are now also "pipable" (comment, blog...), but more will come with new releases.
    • .execute() function lost its cache key argument. This is great news since it was a pain to explain and most cubicweb users didn't know how to handle it well (and I'm thre greatest beneficer since I won't have to explain over and over again)
    • nicer schema and workflow views
    • refactored web session handling, which should now be cleaner, clearer, hence less buggy...
    • nicer skeleton generation for new cubes, cleaner __pkginfo__ (you don't have to define both __depends__ / __depends_cubes__ or __recommends__ / __recommends_cubes__ in the general case, and other cleanups)

    Enjoy!


  • Building my photos web site with CubicWeb part II: security, testing and migration

    2010/04/13 by Sylvain Thenault

    This post will cover various topics:

    • configuring security
    • migrating an existing instance
    • writing some unit tests

    Goal

    Here are the read permissions I want:

    • folders, files, images and comments should have one of the following visibility rules:
      • 'public', everyone can see it
      • 'authenticated', only authenticated users can see it
      • 'restricted', only a subset of authenticated users can see it
    • managers (e.g. me) can see everything
    • only authenticated users can see people
    • everyone can see classifier entities (tag and zone)

    Also, unless explicity specified, the visibility of an image should be the same as the visibility of its parent folder and the visibility of a comment should be the same as the one of the commented entity. If there is no parent entity, the default visibility is 'authenticated'.

    Regarding write permissions, that's much easier:

    • the anonymous user can't write
    • authenticated users can only add comment
    • managers will add the remaining stuff

    Now, let's implement that!

    Proper security in CubicWeb is done at the schema level, so you don't have to bother with it in the views, for the users will only see what they have access to.

    Step 1: adding permissions to the schema

    In the schema, you can grant access according to groups or RQL expressions (users get access if the expression return some results). To implements the read security defined above, groups are not enough, we'll need to use RQL expressions. Here is the idea:

    • add a visibility attribute on folder, image and comment, with a vocabulary ('public', 'authenticated', 'restricted', 'parent')
    • add a may_be_read_by relation that links folder, image or comment to users,
    • add hooks to propagate permission changes.

    So the first thing to do is to modify the schema.py of my cube to define these relations:

    from yams.constraints import StaticVocabularyConstraint
    
    class visibility(RelationDefinition):
        subject = ('Folder', 'File', 'Image', 'Comment')
        object = 'String'
        constraints = [StaticVocabularyConstraint(('public', 'authenticated',
                                                   'restricted', 'parent'))]
        default = 'parent'
        cardinality = '11' # required
    
    class may_be_read_by(RelationDefinition):
        subject = ('Folder', 'File', 'Image', 'Comment',)
        object = 'CWUser'
    

    We can note the following points:

    • we've added a new visibility attribute to folder, file, image and comment using a RelationDefinition
    • cardinality = '11' means this attribute is required. This is usually hidden under the required argument given to the String constructor, but we can rely on this here (same thing for StaticVocabularyConstraint, which is usually hidden by the vocabulary argument)
    • the 'parent' possible value will be used for visibility propagation

    Now, we should be able to define security rules in the schema, based on these new attribute and relation. Here is the code to add to schema.py:

    from cubicweb.schema import ERQLExpression
    
    VISIBILITY_PERMISSIONS = {
        'read':   ('managers',
                   ERQLExpression('X visibility "public"'),
                   ERQLExpression('X visibility "authenticated", U in_group G, G name "users"'),
                   ERQLExpression('X may_be_read_by U')),
        'add':    ('managers',),
        'update': ('managers', 'owners',),
        'delete': ('managers', 'owners'),
        }
    AUTH_ONLY_PERMISSIONS = {
            'read':   ('managers', 'users'),
            'add':    ('managers',),
            'update': ('managers', 'owners',),
            'delete': ('managers', 'owners'),
            }
    CLASSIFIERS_PERMISSIONS = {
            'read':   ('managers', 'users', 'guests'),
            'add':    ('managers',),
            'update': ('managers', 'owners',),
            'delete': ('managers', 'owners'),
            }
    
    from cubes.folder.schema import Folder
    from cubes.file.schema import File, Image
    from cubes.comment.schema import Comment
    from cubes.person.schema import Person
    from cubes.zone.schema import Zone
    from cubes.tag.schema import Tag
    
    Folder.__permissions__ = VISIBILITY_PERMISSIONS
    File.__permissions__ = VISIBILITY_PERMISSIONS
    Image.__permissions__ = VISIBILITY_PERMISSIONS
    Comment.__permissions__ = VISIBILITY_PERMISSIONS.copy()
    Comment.__permissions__['add'] = ('managers', 'users',)
    Person.__permissions__ = AUTH_ONLY_PERMISSIONS
    Zone.__permissions__ = CLASSIFIERS_PERMISSIONS
    Tag.__permissions__ = CLASSIFIERS_PERMISSIONS
    

    What's important in there:

    • VISIBILITY_PERMISSIONS provides read access to an entity:
      • if user is in the 'managers' group,
      • or if visibility attribute's value is 'public',
      • or if visibility attribute's value is 'authenticated' and user (designed by the 'U' variable in the expression) is in the 'users' group (all authenticated users are expected to be in this group)
      • or if user is linked to the entity (the 'X' variable) through the may_be_read_by permission
    • we modify permissions of the entity types we use by importing them and modifying their __permissions__ attribute
    • notice the .copy(): we only want to modify 'add' permission for Comment, not for all entity types using VISIBILITY_PERMISSIONS!
    • remaning parts of the security model is done using regular groups:
      • 'users' is the group to which all authenticated users will belong
      • 'guests' is the group of anonymous users

    Step 2: security propagation in hooks

    To fullfill our requirements, we have to implement:

    Also, unless explicity specified, the visibility of an image should be the same as
    the visibility of its parent folder and the visibility of a comment should be the same as the
    one of the commented entity. If there is no parent entity, the default visibility is
    'authenticated'.
    

    This kind of 'active' rule will be done using CubicWeb's hook system. Hooks are triggered on database event such as addition of new entity or relation.

    The tricky part of the requirement is in unless explicitly specified, notably because when the entity addition hook is executed, we don't know yet its 'parent' entity (eg folder of an image, image commented by a comment). To handle such things, CubicWeb provides Operation, which allow to schedule things to do at commit time.

    In our case we will:

    • on entity creation, schedule an operation that will set default visibility
    • when a "parent" relation is added, propagate parent's visibility unless the child already has a visibility set

    Here is the code in cube's hooks.py:

    from cubicweb.selectors import implements
    from cubicweb.server import hook
    
    class SetVisibilityOp(hook.Operation):
        def precommit_event(self):
            for eid in self.session.transaction_data.pop('pending_visibility'):
                entity = self.session.entity_from_eid(eid)
                if entity.visibility == 'parent':
                    entity.set_attributes(visibility=u'authenticated')
    
    class SetVisibilityHook(hook.Hook):
        __regid__ = 'sytweb.setvisibility'
        __select__ = hook.Hook.__select__ & implements('Folder', 'File', 'Image', 'Comment')
        events = ('after_add_entity',)
        def __call__(self):
            hook.set_operation(self._cw, 'pending_visibility', self.entity.eid,
                               SetVisibilityOp)
    
    class SetParentVisibilityHook(hook.Hook):
        __regid__ = 'sytweb.setparentvisibility'
        __select__ = hook.Hook.__select__ & hook.match_rtype('filed_under', 'comments')
        events = ('after_add_relation',)
    
        def __call__(self):
            parent = self._cw.entity_from_eid(self.eidto)
            child = self._cw.entity_from_eid(self.eidfrom)
            if child.visibility == 'parent':
                child.set_attributes(visibility=parent.visibility)
    

    Remarks:

    • hooks are application objects, hence have selectors that should match entity or relation type to which the hook applies. To match relation type, we use the hook specific match_rtype selector.
    • usage of set_operation: instead of adding an operation for each added entity, set_operation allows to create a single one and to store the eids of the entities to be processed in the session transaction data. This is a good pratice to avoid heavy operations manipulation cost when creating a lot of entities in the same transaction.
    • the precommit_event method of the operation will be called at transaction's commit time.
    • in a hook, self._cw is the repository session, not a web request as usually in views
    • according to hook's event, you have access to different member on the hook instance. Here:
      • self.entity is the newly added entity on 'after_add_entity' events
      • self.eidfrom / self.eidto are the eid of the subject / object entity on 'after_add_relation' events (you may also get the relation type using self.rtype)

    The 'parent' visibility value is used to tell "propagate using parent security" because we want that attribute to be required, so we can't use None value else we'll get an error before we get any chance to propagate...

    Now, we also want to propagate the may_be_read_by relation. Fortunately, CubicWeb provides some base hook classes for such things, so we only have to add the following code to hooks.py:

    # relations where the "parent" entity is the subject
    S_RELS = set()
    # relations where the "parent" entity is the object
    O_RELS = set(('filed_under', 'comments',))
    
    class AddEntitySecurityPropagationHook(hook.PropagateSubjectRelationHook):
        """propagate permissions when new entity are added"""
        __regid__ = 'sytweb.addentity_security_propagation'
        __select__ = (hook.PropagateSubjectRelationHook.__select__
                      & hook.match_rtype_sets(S_RELS, O_RELS))
        main_rtype = 'may_be_read_by'
        subject_relations = S_RELS
        object_relations = O_RELS
    
    class AddPermissionSecurityPropagationHook(hook.PropagateSubjectRelationAddHook):
        __regid__ = 'sytweb.addperm_security_propagation'
        __select__ = (hook.PropagateSubjectRelationAddHook.__select__
                      & hook.match_rtype('may_be_read_by',))
        subject_relations = S_RELS
        object_relations = O_RELS
    
    class DelPermissionSecurityPropagationHook(hook.PropagateSubjectRelationDelHook):
        __regid__ = 'sytweb.delperm_security_propagation'
        __select__ = (hook.PropagateSubjectRelationDelHook.__select__
                      & hook.match_rtype('may_be_read_by',))
        subject_relations = S_RELS
        object_relations = O_RELS
    
    • the AddEntitySecurityPropagationHook will propagate the relation when filed_under or comments relations are added
      • the S_RELS and O_RELS set as well as the match_rtype_sets selector are used here so that if my cube is used by another one, it'll be able to configure security propagation by simply adding relation to one of the two sets.
    • the two others will propagate permissions changes on parent entities to children entities

    Step 3: testing our security

    Security is tricky. Writing some tests for it is a very good idea. You should even write them first, as Test Driven Development recommends!

    Here is a small test case that'll check the basis of our security model, in test/unittest_sytweb.py:

    from cubicweb.devtools.testlib import CubicWebTC
    from cubicweb import Binary
    
    class SecurityTC(CubicWebTC):
    
        def test_visibility_propagation(self):
            # create a user for later security checks
            toto = self.create_user('toto')
            # init some data using the default manager connection
            req = self.request()
            folder = req.create_entity('Folder',
                                       name=u'restricted',
                                       visibility=u'restricted')
            photo1 = req.create_entity('Image',
                                       data_name=u'photo1.jpg',
                                       data=Binary('xxx'),
                                       filed_under=folder)
            self.commit()
            photo1.clear_all_caches() # good practice, avoid request cache effects
            # visibility propagation
            self.assertEquals(photo1.visibility, 'restricted')
            # unless explicitly specified
            photo2 = req.create_entity('Image',
                                       data_name=u'photo2.jpg',
                                       data=Binary('xxx'),
                                       visibility=u'public',
                                       filed_under=folder)
            self.commit()
            self.assertEquals(photo2.visibility, 'public')
            # test security
            self.login('toto')
            req = self.request()
            self.assertEquals(len(req.execute('Image X')), 1) # only the public one
            self.assertEquals(len(req.execute('Folder X')), 0) # restricted...
            # may_be_read_by propagation
            self.restore_connection()
            folder.set_relations(may_be_read_by=toto)
            self.commit()
            photo1.clear_all_caches()
            self.failUnless(photo1.may_be_read_by)
            # test security with permissions
            self.login('toto')
            req = self.request()
            self.assertEquals(len(req.execute('Image X')), 2) # now toto has access to photo2
            self.assertEquals(len(req.execute('Folder X')), 1) # and to restricted folder
    
    if __name__ == '__main__':
        from logilab.common.testlib import unittest_main
        unittest_main()
    

    It is not complete, but it shows most of the things you will want to do in tests: adding some content, creating users and connecting as them in the test, etc...

    To run it type:

    [syt@scorpius test]$ pytest unittest_sytweb.py
    ========================  unittest_sytweb.py  ========================
    -> creating tables [....................]
    -> inserting default user and default groups.
    -> storing the schema in the database [....................]
    -> database for instance data initialized.
    .
    ----------------------------------------------------------------------
    Ran 1 test in 22.547s
    
    OK
    

    The first execution is taking time, since it creates a sqlite database for the test instance. The second one will be much quicker:

    [syt@scorpius test]$ pytest unittest_sytweb.py
    ========================  unittest_sytweb.py  ========================
    .
    ----------------------------------------------------------------------
    Ran 1 test in 2.662s
    
    OK
    

    If you do some changes in your schema, you'll have to force regeneration of that database. You do that by removing the tmpdb* files before running the test:

    [syt@scorpius test]$ rm tmpdb*
    

    BTW, pytest is a very convenient utilities to control test execution, from the logilab-common package.

    Step 4: writing the migration script and migrating the instance

    Prior to those changes, Iv'e created an instance, fed it with some data, so I don't want to create a new one, but to migrate the existing one. Let's see how to do that.

    Migration commands should be put in the cube's migration directory, in a file named file:<X.Y.Z>_Any.py ('Any' being there mostly for historical reason).

    Here I'll create a migration/0.2.0_Any.py file containing the following instructions:

    add_relation_type('may_be_read_by')
    add_relation_type('visibility')
    sync_schema_props_perms()
    

    Then I update the version number in cube's __pkginfo__.py to 0.2.0. And that's it! Those instructions will:

    • update the instance's schema by adding our two new relations and update the underlying database tables accordingly (the two first instructions)
    • update schema's permissions definition (the later instruction)

    To migrate my instance I simply type:

    [syt@scorpius ~]$ cubicweb-ctl upgrade sytweb
    

    I will then be asked some questions to do the migration step by step. You should say YES when it asks if a backup of your database should be done, so you can get back to the initial state if anything goes wrong...

    Conclusion

    This is a somewhat long post that I bet you will have to read at least twice ;) There is a hell lot of information hidden in there... But that should start to give you an idea of CubicWeb's power...

    See you next time for part III !


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