When I switched co.mments to use the new feeds about a week ago, I made a mistake. As far as I know, it only affects Bloglines users (kwc was first to report it). Even if a conversation had no new comments, Bloglines would still mark it as updated.

Since Bloglines checks the feeds automatically, I couldn’t test it fast enough. I had to make a change, wait a few hours for Bloglines to check the feed again, test the results, try something else, etc. So it took a while, but I finally fixed it.

Unfortunately, due to that problem (and its fix), all your conversations may show up as unread the next time you check Bloglines. This will happen only once, and then things will go back to normal. I apologize for that.

Technical Details

Read this is you want to know the gory technical details.
When Blogline (or any feed reader) asks the co.mments server for an update, it receives a feed that is generated to show all the last updates. If there are new comments since last checked, the feed will include recently updated conversations that show these new comments, but also conversations (and comments) you’ve seen before.

Why repeat the same content? All feeds do that and feed readers are designed to deal with that. It means that if your feed reader stops working, the data in your feed is not lost. It also lets you use more than one feed reader, or share your feeds with other people.

The feed readers I use for testing co.mments ignore old items. If they get a feed with the same item (and most feeds include older items), they simply ignore them and only display the new ones.

Bloglines is a bit smarter, it actually looks at the contents of the item. If it sees that the item has the same name, but the content changed, it marks that item as new.

Each feed tells you when the conversation was last updated and used to do it with relatives times (e.g. “3 hours ago”). Each time Bloglines reads the feed it gets slightly different content. Three hours later, it would say “6 hours ago”. Bloglines consider this an update and marks the feed item as unread.

I fixed that by changing all times to absolute, instead of “3 hours ago” the feed will say “Apr 30, 2006 7pm”. And on the next check it will still show the same time. Bloglines will consider it the same item and won’t mark it as unread.

Since I’ve changed all items in the feed from relative to absolute times, Bloglines will consider every item in your feed to be an update and mark the entire feed as unread. But only once, the next time it checks the feed. Afterwards, it will only mark new items as unread.

Posted by Assaf in General on Sunday, April 30th, 2006. You can follow any responses using co.mments, leave a response, or trackback from your own site.