alt Hacker NewsThe problem is that they are not enforced. You can already have GET requests that modify state even though they are not supposed to.
What you are actually doing when making a specific kind of request is assuming the actual properties match the documented properties and acting accordingly.
A QUERY seems to be no more than a POST that documents it is idempotent. Furthermore, you should only QUERY a resource that has advertised it is idempotent via the “Accept-Query” header. You might as well name that the “Idempotent-Post” header and then you just issue a POST; exactly the same information and properties were expressed and you do not need a new request type to support it.
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HTTP semantics aren’t hard enforced but that only means something if you always control the client, server, and all the middle layers like proxies or CDNs that your traffic flows over.
Your GET request can modify state. But if your request exceeds a browser’s timeout threshold, the browser will retry it. And then you get to spend a few days debugging why a certain notification is always getting sent three times (ask me how I know this)
Similarly, you can put a body on your GET request in curl. But a browser can’t. And if you need to move your server behind cloudflare one day, that body is gonna get dropped.
I'm confused - wouldn't idempotent POST be PUT? Isn't the proposed QUERY for fetching semantics?
It would be pretty impossible to actually ‘enforce’ that GETs don’t modify state. I am not sure if I would call the lack of enforcement a problem when it is more a simple fact about distributed systems; no specification can enforce what a service does outside of the what is returned in a response.
> A QUERY seems to be no more than a POST that documents it is idempotent.
This is false.
By design QUERY is both safe and idempotent. In the context of HTTP, safe means "read-only", whereas idempotent means that a method does not introduce changes on the server, and thus many requests have the same effect of posting a single request.
The fact that the semantics of an operation is deemed safe has far-reaching implications in the design of any participant of a HTTP request, including firewalls, load balancers, proxies.
> You might as well name that the “Idempotent-Post” header and then you just issue a POST;
This is outright wrong, and completely ignores the semantics of a POST request. POST requests by design are neither safe not idempotent. You do not change that with random request headers.