7 Matching Annotations
  1. Jul 2021
    1. So long as the filters are only using GET requests to pull down links, there’s nothing fundamentally wrong with them. It’s a basic (though oft-ignored) tenet of web development that GET requests should be idempotent; that is, they shouldn’t somehow change anything important on the server. That’s what POST is for. A lot of people ignore this for convenience’s sake, but this is just one way that you can get bitten. Anyone remember the Google Web Accelerator that came out a while ago, then promptly disappeared? It’d pre-fetch links on a page to speed up things if you clicked them later on. And if one of those links happened to delete something from a blog, or log you out… well, then you begin to see why GET shouldn’t change things. So yes, the perfect solution to this is a 2-step unsubscribe link: the first step takes to you a page with a form on it, and that form then POSTs something back that finalizes the unsubscribe request.
    2. Idempotent just means that following a link twice has exactly the same effect on persistent state as clicking it once. It does not mean that following the link must not change state, just that after following it once, following it again must not change state further. There are good reasons to avoid GET requests for changing state, but that’s not what idempotent means.