Tag Feeds for null program

I just added a formal tags page along with individual feeds for each tag. I’ve had tags for a couple of years now, but they were really only useful for traveling sideways to similar articles. So now, if you’re only interested in a subset of my content, you can subscribe to one or more tags rather than the main Atom feed.

What prompted this? In my Emacs Chat, Sacha asked me if this blog was part of Planet Emacsen (currently, it’s not). If my tags are accurate, only about 25% of my articles are about Emacs, so most of my blog isn’t relevant there. Tag feeds will go a long way to help support these “planet” aggregators, should they want to include my articles. For example, Planet Emacsen would use my Emacs feed.

Static Site Generation

I couldn’t practically support these extra feeds until recently. Remember, this blog is statically generated. More feeds means more content to generate, because articles are duplicated in whole for each feed. In past years, Jekyll would probably take on the order of an hour to do all this for a single build. Fortunately, Jekyll has improved dramatically, especially in the past year or so, and these feeds have little impact on the total build time. It’s currently around 10 seconds or so. Not bad at all!

A consequence of being statically generated is that you can’t ask for a combination of tags as a single feed. It would be a combinatorial nightmare (billions of feeds). Plus, the request would have to normalize the tag order (e.g. alphabetical) or else the combinatorial explosion to be far worse (i.e. exceeding the number of atoms in the universe). So I hope you can forgive me when subscribing to each tag individually.

Duplicate Articles

What if an article matches multiple tags? It will appear in each feed where it’s tagged, possibly showing up multiple times in your web feed reader. Fortunately, this is where Atom saves the day! I’m leveraging Atom’s prudent design to make this work cleanly. Articles’ UUIDs are consistent across all of these feeds, so if your web feed reader is smart enough, it will recognize these as being the same article. For example, this article is f47e5404-cc4a-3cc0-01ce-a844c04721b8 regardless of which feed you see it in.

Unfortunately, Elfeed isn’t smart enough for this. Sorry! In order to better support all the broken RSS feeds out there, I had to compromise on entry keying. I couldn’t trust RSS feeds to provide me a reasonably unique key, so, transitively, Elfeed doesn’t fully trust Atom’s UUIDs either. These RSS feeds are broken largely because RSS itself is a broken mess. When making new feeds in the future, please use Atom!

Atom requires that every feed and article have a proper UUID. It doesn’t matter where you get the feed from. You could subscribe to the same exact feed at three different URLs (mirrors perhaps) and your reader could reliably use the UUIDs to avoid duplication. Or, if you’re subscribed to an aggregator like Planet Emacsen, and it includes content from a feed to which you’re also directly subscribed, your reader client should be able to merge these articles. In comparison, RSS not only doesn’t require UUIDs, it actively discourages them with its broken guid tag, so merging content from multiple sources is impossible with RSS.

Anyway, if most of my content doesn’t suit you, you can now subscribe to the subset that does. Aren’t Atom feeds cool?

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null program

Chris Wellons