The main task I worked on during the sprint with Alex and Matthew was making PloneSoftwareCenter ready for the new version of Plone.org. These guys rock. We did tons of things and the new plone.org website is coming up. Alex worked for quite a while on migrating plone.org to plone 3, but let me focus on the software center part.
First of all, let me explain what is the final goal of the work done in the software center.
The future of Plonistas: a 100 % egg-based world and what is means
Since a few years, Zope code base was moved into a set of namespaced packages. Plone is following closely. From there zc.buildout is providing a simple way to pick up the right set of packages to build an application. This set is automatically chosen by recipes at Zope and Plone level. Then developers add their own packages and dependencies to provide custom features in their applications.
This mechanism means that each team has to:
- make distributions of packages (tarball, eggs, ..) - build the application with buildout, then release a source distribution - and provide a way for other developers to build the application on their own, by:
- publishing the buildout configuration files - pushing the packages the buildout uses into to a server that is reachable by developers - make sure Plone and Zope packages are also reachable
This means that each team is responsible at least to release packages.
Distutils and Cheeseshop
Distutils provides two commands to publish packages to the world: register and upload. These commands were intended to provide to the developer a way to push packages to any server that supports the protocol, by using the --repository option.
But in reality, the only server that is publicly available is the Cheeseshop (pypi.python.org). Furthermore Distutils is not providing everything needed to work with another server than the Cheeseshop, like I will explain later in this post. So all Plone and Zope packages are uploaded there.
Therefore, pypi.python.org became a single point of failure when you need to build a Plone or Zope application. With the growth of the community, this means that the repository will get bigger and have to deal with more and more request. PyPI weight around 4 gigas at this time, of zip files and tarballs.
While the actual server is really fast, it makes it a bit hard to work when it is down. It didn't happen often. Twice as far as I remember. But when it happens, the crowd that uses zc.buildout is frozen because they run buildouts several time per day. They can use cache of course, as long as those are up-to-date.
Some mirrors emerged, like http://release.ingeniweb.com/pypi.python.org-mirror. Some enhanced indexes were created as well, like http://download.zope.org/simple, which is still referring to pypi.python.org but performs a bit of crawling to speed things up when a buildout uses it through easy_install.
But all of these are just enhancement to a cheeseshop-centric model.
Furthermore, in case of a private application, you do not want to see packages in the Cheeseshop but you might also want to provide developers a similar way to manage and use them.
Plone.org software center is dying !
For public applications, given the fact that Distutils provides a simple way to push a package to a public location (one shell command), people have started to stop updating the Products section of Plone.org. This happens because updating it means doing a whole lot more than the simple register+upload call. You need to login into the website, then manually upload the packages, then change the front page of the product if needed etc..
So being able to push packages to plone.org with the same set of commands, is the right solution for developers.
Pushing a package means uploading a public archive but it also means updating the front page for the given package, with the register command.
That what I worked on, at PloneSoftwareCenter level, continuing Sidnei's work: making it act like Cheeseshop. Now the feature is ready and being alpha-tested at new.plone.org
Toward a distributed model
What we will be able to do from there, is to distribute packages (in blue) to the Cheeseshop (2) as usual, but also to Plone.org (1). Having such a tool also allows people to run other cheeseshop-like servers, wether they are public (3) or private (4). This is useful when you are working on customer projects and do not wish to make their packages available to the world, or even if it is a public project, you do not want to push them to PyPi.
Furthermore, it allows having a bit of redundancy : your packages become available in several places, which is better. Think about the mirrors at Sourceforge, same thing here...
This distributed model is used at Ingeniweb, and in other companies I am starting to list (If you do please let me know, this is important to promote the tool).
The new Plone Software Center (PSC)
If you are extensively working with packages and buildouts, you should consider trying the new PSC, read http://tarekziade.wordpress.com/2008/03/20/how-to-run-your-own-private-pypi-cheeseshop-server/ for this. Each project now in the software center can hold several eggs, and it makes it possible to provide a nice deployment model for your teams: developer push packages releases in such a server with the distutils standards, while customers or deployers can build their applications by picking them up through their buildouts.
And it is in Plone, so you can provide extensive features, like a bug tracker, and all the sweet things Plonecan provide.
The work left to be done in PSC is :
- making the storage for archives (tgz, egg) pluggable so new storing strategies can be provided in separate packages, under the collective.psc namespace, I started this work in a branch. - finish the collective.psc.mirroring package, that will be used in plone.org to fill a system folder, in order to provide an Apache direct view over the archives stored. This will make zc.buildout / easy_install use this stream rather than hitting the Plone instance. Although the final goal will be to transform it into a storage strategy, but time is running and this is useful now for plone.org. - extensive tests on new.plone.org
To be able to deal with several servers, I have released collective.dist after the sprint (previously iw.dist). This package provides two new distutils commands: mupload and mregister, together with a new pypirc format.
Follow the documentation, and you will be set in a matter of minutes. This package is already used by many developers to make their life easier, and will help you when the new plone.org goes live.
collective.dist is an evolution of distutils I have been working at Python level for months. It is available as a Python patch here : http://bugs.python.org/issue1858. mregister and mupload are just modified register and upload commands that makes it possible to interact with several PyPi-like servers, that's it. PSC uses Distutils standards in any case, so it is possible to use the regular register and upload commands with it of course. It is just not convenient because you will need to have the same username and password on both CheeseShop and the third-party egg server (or change your pypirc file everytime :D)
So the patch, basically, just makes the -r option of distutils commands a 100% operational.
Now my job is to convince Python core developers it should be integrated into Python 2.6, and I am working on this. It is a logical evolution, but it sounds overkill to some people that does not have this kind of need: "Why changing that ? we have only one package server, which is the cheeseshop".
It can also sound to some of them like I am (together with the team of 20 developers we have ;) ) the only person on earth that wishes it, but as soon as the new Plone.org will be online, a lot of people will start needing such a feature. But having it in 2.6 will make it available as a standard in Plone/Zope world in... a few years.
In any case, most of them agree in the fact that this change is logical and that the current pypirc format is not to be kept. So I guess it is just a matter of time and patience.