Idempotent means that you can apply the operation a number of times, but the resulting state of one call will be indistinguishable from the resulting state of multiple calls. In short, it is safe to call the method multiple times. Effectively the second and third (and so on) calls will have no visible effect on … Read more
The only advantage of POST-creation over PUT-creation is the server generation of IDs. I don’t think it worths the lack of idempotency (and then the need for removing duplicates or empty objets). Instead, I would use a PUT with a UUID in the URL. Owing to UUID generators you are nearly sure that the ID … Read more
In more simple terms: Pure deterministic function: The output is based entirely, and only, on the input values and nothing else: there is no other (hidden) input or state that it relies on to generate its output. There are no side-effects or other output. Impure deterministic function: As with a deterministic function that is a … Read more
I asked this question on the HTTP mailing list and was told that idempotency does not include return codes. Meaning, you are free to return HTTP 204 the first time a resource is deleted, and HTTP 404 at a later time, so long as the subsequent request does not change the server state. While it … Read more
This question is very similar to Implementing secure, unique “single-use” activation URLs in ASP.NET (C#). My answer there is close to your scheme, with a few issues pointed out – such as short period of validity, handling double signups, etc. Your use of a cryptographic nonce is also important, that many tend to skip over … Read more
An idempotent function can cause idempotent side-effects. A pure function cannot. For example, a function which sets the text of a textbox is idempotent (because multiple calls will display the same text), but not pure. Similarly, deleting a record by GUID (not by count) is idempotent, because the row stays deleted after subsequent calls. (additional … Read more
As HTTP requests in a stateless system should be independent, the results of one request should not be dependent on a previous request. Consider what should happen if two users did a DELETE on the same resource simultaneously. It makes sense for the second request to get a 404. The same should be true if … Read more
In computing, an idempotent operation is one that has no additional effect if it is called more than once with the same input parameters. For example, removing an item from a set can be considered an idempotent operation on the set. In mathematics, an idempotent operation is one where f(f(x)) = f(x). For example, the … Read more