Move documentation from pythonhosted.org to readthedocs.io

Today we migrated the documentation of zodb.py3migrate from pythonhosted.org to zodbpy3migrate.readthedocs.io.

This requires a directory – for this example I name it redir – containing a file named index.html with the following content:

<html>
<head>
 <title>zodb.py3migrate</title>
 <meta http-equiv="refresh"
       content="0; url=http://zodbpy3migrate.rtfd.io" />
</head>
<body>
  <p>
    <a href="http://zodbpy3migrate.rtfd.io">
      Redirect to zodbpy3migrate.rtfd.io
    </a>
  </p>
</body>
</html>

To upload it to pythonhosted.org I called:

py27 setup.py upload_docs --upload-dir=redir

Now pythonhosted.org/zodb.py3migrate points to read the docs.

Credits: The HTML was taken from the Trello board of the avocado-framework.

Zope 2 Resurrection Sprint – Goal accomplished

The sprint days were really busy for Earl Zope II and the people helping him with the Python 3 wonderland immigration authorities.

  • Zope
    • can be installed using Python 3
    • can be started and renders some views
    • has more than 1.700 of more than 2.300 tests running
    • has some optional dependencies left to be ported.
  • To accomplished this by:
    • Complete porting of RestrictedPython, so a first alpha release with the new implementation was released. (This includes about 260 commits, nearly 100 files changed, 9.000 lines of newly written code and 1.000 lines of code deleted.)
    • Port AccessControl to Python 3. This port covers the Python code of the package.
    • Make an alpha release of DocumentTemplate which supports Python 3. It is purely based on Python code. (Thanks Hanno for the porting work from C to Python!)
    • Note: There were problems porting AccessControl and DocumentTemplate to PyPy so we left this out for now. (Volunteers welcome!)

Besides working on Zope there was other ongoing work:

His majesty Earl Zope II says a warm “Thank you!” to all who helped him to start his new live in Python 3 wonderland. There is still enough work to be done so he can live there and having all the comfort and stability of Python 3. See you on the next sprint!

Towards RestrictedPython 3

The biggest blocker to port Zope to Python 3 is RestrictedPython.

What is RestrictedPython?

It is a library used by Zope to restrict Python code at instruction level to a bare minimum of trusted functionality. It parses and filters the code for not allowed constructs (such as open()) and adds wrappers around each access on attributes or items. These wrappers can be used by Zope to enforce access control on objects in the ZODB without requiring manual checks in the code.

Why is RestrictedPython needed?

Zope allows writing Python code in the Zope management interface (ZMI) using a web browser (“through the web” aka TTW). This code is stored in the ZODB. The code is executed on the server. It would be dangerous to allow a user to execute arbitrary code with the rights of the web server process. That’s why the code is filtered through RestrictedPython to make sure this approach is not a complete security hole.

RestrictedPython is used in many places of Zope as part of its security model. An experiment on the Zope Resurrection Sprint showed that it would be really hard to create a Zope version which does not need RestrictedPython thus removing the TTW approach.

What is the problem porting RestrictedPython to Python 3?

RestrictedPython relies on the compiler package of the Python standard library. This package no longer exists in Python 3 because it was poorly documented, unmaintained and out of sync with the compiler Python uses itself. (There are whisperings that it was only kept because of Zope.)

Since Python 2.6 there is a new ast module in the Python standard library which is not a direct replacement for compiler. There is no documentation how to replace compiler by ast.

What is the current status?

Several people already worked on various Plone and Zope sprints and mostly in their spare time on a Python 3 branch of RestrictedPython to find out how this package works and to start porting some of its functionality as a proof of concept. It seems to be possible to use ast as the new base for RestrictedPython. Probably the external API of RestrictedPython could be kept stable. But packages using or extending some of the internals of RestrictedPython might need to be updated as well.

What are the next steps?

Many Zope and Plone packages depend on RestrictedPython directly (like AccessControl or Products.ZCatalog) or indirectly (like Products.PythonScripts, plone.app.event or even plone.app.dexterity).

When RestrictedPython has successfully been tested against these packages porting them can start. There is a nice list of all Plone 5.1 dependencies and their status regarding Python 3.

Our goal is to complete porting RestrictedPython by the end of March 2017. It opens up the possibility guiding Zope into the Python 3 wonderland by the end of 2017. This is ambitious, especially if the work is done in spare time besides the daily customer work. You can help us by either contributing PullRequests via Github or review them.

We are planning two Zope sprints in spring and autumn 2017. Furthermore we are grateful for each and every kind of support.

Zope Resurrection Part 2 – Defibrillation

After reanimation we started defibrillation of Zope and … it kinda worked:

On our sprint we got the following things done to help Zope in the Python 3 wonderland:

As grok builds on the ZTK, it is a beneficiary of the reanimation. The following steps have been undertaken to lead it to the Python 3 wonderland:

We have had a discussion about the broader future of Zope:

  • There could be more optional dependencies like ZServer in Zope 4.
  • The ZMI could be removed altogether because it was not maintained any more for years. It should not be used by applications built on top of Zope anyway. Plone even suggests to block public access to the ZMI.
  • There is a road map needed for Zope 4 so the Plone community can pick it up as decided in the Zope 4 PLIP.
  • Further discussions should be held on the zope-dev list and in the issue trackers of the  Zope foundation on Github. This seems to be the way to get most people involved who are interested in the future of Zope.

Conclusion: Zope is not dead. On the sprint there were nearly 20 people who use Zope for their daily work. Some of them even joined the sprint without the backup of a company in their spare time. Yes, it will need time and effort to keep Zope alive and make it prosper in the Python 3 wonderland, but Zope is still needed and has its place in the audience of web frameworks.

We at gocept will keep Zope as part of our supported technology stack in the projects it fits the purpose and will offer help to others who need to migrate a long term project into the future. We will be at the PyConDE in Munich at the end of October and will be open for questions and further discussions. Do not hesitate to talk to us.

 

Zope Resurrection Part 1 – Reanimation

Now we are helping Zope in the Python 3 wonderland: Almost 20 people started with the reanimation of Zope. We are working mostly on porting important dependencies of Zope to Python 3:

Zope 4 is now per default based on WSGI. Thanks to Hanno who invested much time to make the WSGI story of Zope much more streamlined.

We found out that the ZTK (Zope Toolkit) is no longer used in any of the projects using packages of it (Zope, Grok, Bluebream – as it is dead). It should be kept to test compatibility between the packages inside the ZTK.

zodb.py3migrate: Migrate an existing ZODB Data.fs to be used with Python 3

At Berlin Strategic sprint 2016 we developed a tool to analyze a ZODB Filestorage to find Python 2 string objects. If they are in an encoding besides ASCII this is preventing using this Filestorage with Python 3 because of decoding errors arising on loading the pickles.
The tool is even able to convert those strings either to unicode by decoding them using a configurable encoding or convert them to zodbpickle.binary so Python 3 will read them as bytes.
There is documentation of the tool and a repository on GitHub where the code lives.

There are still some questions open:

  • Is there already another tool for this analysis/migration?
  • Is there already any practical knowledge migrating Filestorage contents to Python 3?
  • Do you think such a tool is the right approach to achieve such a migration?
  • Is there anyone who wants to try out the tool on a Filestorage of a personal project and share the experiences? (We analyzed two projects where we have access to a Filestorage but we are sure this does not catch all the edge cases.)