I’ve been off the air for several days due to a hosting-site failure last Friday. After several months of deteriorating performance and various services being sporadically inaccessible, Berlios’s webspace went 404 and the Subversion repositories stopped working…taking my GPSD project down with them. I had every reason to fear this might be permanent, and spent the next two days reconstructing as much as possible of the project state so we could migrate to another site.
Berlios came back up on Monday. But I don’t trust it will stay that way. This weekend rubbed my nose in some systemic vulnerabilities in the open-source development infrastructure that we need to fix. Rant follows.
1. Hosting Sites Are Data Jails
The worst problem with almost all current hosting sites is that they’re data jails. You can put data (the source code revision history, mailing list address lists, bug reports) into them, but getting a complete snapshot of that data back out often ranges from painful to impossible.
Why is this an issue? Very practically, because hosting sites, even well-established ones, sometimes go off the air. Any prudent project lead should be thinking about how to recover if that happens, and how to take periodic backups of critical project data. But more generally, it’s your data. You should own it. If you can’t push a button and get a snapshot of your project state out of the site whenever you want, you don’t own it.
When berlios.de crashed on me, I was lucky; I had been preparing to migrate GPSD off the site due to deteriorating performance; I had a Subversion dump file that was less than two weeks old. I was able to bring that up to date by translating commits from an unofficial git mirror. I was doubly lucky in that the Mailman adminstrative pages remained accessible even when the project webspace and repositories had been 404 for two days.
But actually retrieving my mailing-list data was a hideous process that involved screen-scraping HTML by hand, and I had no hope at all of retrieving the bug tracker state.
This anecdote illustrates the most serious manifestations of the data-jail problem. Third-generation version-control (hg, git, bzr, etc.) systems pretty much solve it for code repositories; every checkout is a mirror. But most projects have two other critical data collections: their mailing-list state and their bug-tracker state. And, on all sites I know of in late 2009, those are seriously jailed.
This is a problem that goes straight to the design of the software subsystems used by these sites. Some are generic: of these, the most frequent single offender is 2.x versions of Mailman, the most widely used mailing-list manager (the Mailman maintainers claim to have fixed this in 3.0). Bug-trackers tend to be tightly tied to individual hosting engines, and are even harder to dig data out of. They also illustrate the second major failing…
2. Hosting Sites have Poor Scriptability
All hosting-site suites are Web-centric, operated primarily or entirely through a browser. This solves many problems, but creates a few as well. One is that browsers, like GUIs in general, are badly suited for stereotyped and repetitive tasks. Another is that they have poor accessibility for people with visual or motor-control issues.
Here again the issues with version-control systems are relatively minor, because all those in common use are driven by CLI tools that are easy to script. Mailing lists don’t present serious issues either; the only operation on them that normally goes through the web is moderation of submissions, and the demands of that operation are fairly well matched to a browser-style interface.
But there are other common operations that need to be scriptable and are generally not. A representative one is getting a list of open bug reports to work on later – say, somewhere that your net connection is spotty. There is no reason this couldn’t be handled by an email autoresponder robot connected to the bug-tracker database, a feature which would also improve tracker accessibility for the blind.
Another is shipping a software release. This normally consists of uploading product files in various shipping formats (source tarballs, debs, RPMs, and the like) to the hosting site’s download area, and associating with them a bunch of metadata including such things as a short-form release announcement, file-type or architecture tags for the binary packages, MD5 signatures, and the like.
With the exception of the release announcement, there is really no reason a human being should be sitting at a web browser to type in this sort of thing. In fact there is an excellent reason a human shouldn’t do it by hand – it’s exactly the sort of fiddly, tedious semi-mechanical chore at which humans tend to make (and then miss)finger errors because the brain is not fully engaged.
It would be better for the hosting system’s release-registration logic to accept a job card via email, said job card including all the release metadata and URLs pointing to the product files it should gather for the release. Each job card could be generated by a project-specific script that would take the parts that really need human attention from a human and mechanically fill in the rest. This would both minimize human error and improve accessibility.
In general, a good question for hosting-system designers to be asking themselves about each operation of the system would be “Do I provide a way to remote-script this through an email robot or XML-RPC interface or the like?” When the answer is “no”, that’s a bug that needs to be fixed.
3. Hosting Sites Have Inadequate Support for Immigration
The first (and in my opinion, most serious) failing I identified is poor support for snapshotting and if necessary out-migrating a project. Most hosting systems do almost as badly at in-migrating a project that already has a history, as opposed to one started from nothing on the site.
Even uploading an existing source code repository at start of a project (as opposed to starting with an empty one) is only spottily supported. Just try, for example, to find a site that will let you upload a mailbox full of archives from a pre-existing development list in order to re-home it at the project’s new development site.
This is the flip side of the data-jail problem. It has some of the same causes, and many of the same consequences too. Because it makes re-homing projects unnecessarily difficult, it means that project leads cannot respond effectively to hosting-site problems. This creates a systemic brittleness in our development infrastructure.
Addressing the Problems
I believe in underpromising and overperforming, so I’m not going to talk up any grand plans to fix this. Yet. But I will say that I intend to do more than talk. And two days ago the project leaders of Savane, the hosting system that powers gna.org and Savanna, read this and invited me to join their project team.