Deploying Fedora 18 documentation: learning git the hard way

If you haven’t heard, the Fedora team released Fedora 18 today. It’s the culmination of many months of effort, and some very frustrating schedule delays. I’m sure everyone was relieve to push it out the door, even as some contributors worked to make sure the mirrors were stable and update translations. I remembered that I had forgotten to push the Fedora 18 versions of the Live Images Guide and the Burning ISOs Guide, so I quickly did that. Then I noticed that several of the documents that were on the site earlier weren’t anymore. Crap.

Here’s how the Fedora Documentation site works: contributors write guides in DocBook XML, build them with a tool called publican, and then check the built documents into a git repository. Once an hour, the web server clones the git repo to update the content on the site. Looking through the commits, it seemed like a few hours prior, someone had published a document without updating their local copy of the web repo first, which blew away previously-published Fedora 18 docs.

The fix seemed simple enough: I’d just revert to a few commits prior and then we could re-publish the most recent updates. So I git a `git reset –hard` and then tried to push. It was suggested that a –force might help, so I did. That’s when I learned that this basically sends the local git repo to the remote as if the remote were empty (someone who understands git better would undoubtedly correct this explanation), which makes sense. For many repos, this probably isn’t too big a deal. For the Docs web repo, which contains many images, PDFs, epubs, etc. and is roughly 8 GB on disk, this can be a slow process. On a residential cable internet connection which throttles uploads to about 250 KiB/s after the first minute, it’s a very slow process.

I sent a note to the docs mailing list letting people know I was cleaning up the repo and that they shouldn’t push any docs to the web. After an hour or so, the push finally finished. It was…a failure? Someone hadn’t seen my email and pushed a new guide shortly after I had started the push-of-doom. Fortunately I discovered the git revert command in the meantime. revert, instead of pretending like the past never happened, makes diffs to back out the commit(s). After reverting four commits and pushing, we were back to where we were when life was happy. It was simple to re-publish the docs after that, and a reminder was sent to the group to ensure the repo is up-to-date before pushing.

The final result is that some documents were unavailable for a few hours. The good news is that I learned a little bit more about git today. The better news is that this should serve as additional motivation to move to Publican 3, which will allow us to publish guides via RPMs instead of an unwieldy git repo.

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