ikiwiki/ tips/ howto avoid flooding aggregators

If you have a blog that is aggregated, either on a site like Planet Debian, or just through user subscriptions, one common problem is that changes to the guids of items in the blog can “flood” the aggregator, causing all recent blog entries to be posted to the top of it.

This can happen in a lot of situations:

- Perhaps you’ve just switched to ikiwiki from some other blog engine and imported your data.
- Perhaps you’ve turned on the `usedirs` setting, which changes all the urls in your wiki. Even if you set up redirections for the old urls, you still face the issue of flooding aggregators.
- Perhaps you’ve just moved stuff around in your wiki.

To avoid annoying readers in these situations, it’s a good idea to remove any existing items from your blog’s news feed. That way only new items will show up in the aggregator. The best way to do this is to add a `feedpages` parameter to the `inline` directive for your blog, with a condition such as:

    feedpages=created_after(blog/posts/old_post)

Where “old_post” is the name of the last post you made to the blog before making the change. This will limit the feed to only newer posts, while still displaying the old posts in the blog page.

Alternatively, you can add the meta guid directives to pages, to force the old url to be used.