Hacker News Reader

Comment by OvervCW | Hacker News Reader

There is: your browser or other type of client does not know it can repeat a POST request if it fails, whereas a QUERY request can be freely repeated in case of errors.

View on HN

Not freely. It is idempotent, not safe. So it still can have serious load consequences.

    Unlike POST, however, the method is explicitly safe and idempotent, allowing
    functions like caching and automatic retries to operate.

Putting something in a spec does not automatically make it true. In the real world if you repeat expensive queries more than an undefined amount you get blocked or at least bot-checked.

From the browser POV it doesn't need to ask if you want to re-send data.

Putting something in a spec does not automatically make it true.

Terrible news for computing.

The point is that you need to take care to make the implementation of that endpoint safe. It isn’t safe magically by itself.

Great, got it. I'll update my running "how computing works" chart with this new information:

  | implementation = reality | magic  |
  |-----------------------------------|
  | 999,999,999,971 (+1)     | 0      |

Why the snark? The existing methods have been around for ages. Many engineers I’ve encountered were not even aware that there was a distinction between “idempotent” and “safe” as attributes of a method and generally conflated them, using “safe” in the sense of the dictionary definition instead of the spec’s.

Elsewhere it was suggested that we can now replace POST with this query. I was trying to be cautionary because just changing the method alone will bring different behaviour. I did so in brevity because I was in a rush. IMHO, that does not call for snark.

Yes. That is what the spec says. However, if the search query is expensive you need some form of caching. Either on the endpoint itself caching the data, or the mechanism with location to redirect to the location of the result.

Reply on news.ycombinator.com