What are Idempotent methods? How is it relevant in RESTful web services domain?

DWQA QuestionsCategory: Web Design HTMLWhat are Idempotent methods? How is it relevant in RESTful web services domain?
Editor Staff asked 1 month ago

What are Idempotent methods? How is it relevant in RESTful web services domain?

1 Answers
Editor Staff answered 1 month ago

The meaning of idempotent is that even after calling a single request multiple times, the outcome of the request should be the same. While designing REST APIs, we need to keep in mind to develop idempotent APIs. This is because the consumers can write client-side code which can result in duplicate requests intentionally or not. Hence, fault-tolerant APIs need to be designed so that they do not result in erroneous responses.

  • Idempotent methods ensure that the responses to a request if called once or ten times or more than that remain the same. This is equivalent to adding any number with 0.
  • REST provides idempotent methods automatically. GET, PUT, DELETE, HEAD, OPTIONS, and TRACE are the idempotent HTTP methods. POST is not idempotent.
    • POST is not idempotent because POST APIs are usually used for creating a new resource on the server. While calling POST methods N times, there will be N new resources. This does not result in the same outcome at a time.
    • Methods like GET, OPTIONS, TRACE, and HEAD are idempotent because they do not change the state of resources on the server. They are meant for resource retrieval whenever called. They do not result in write operations on the server thereby making it idempotent.
    • PUT methods are generally used for updating the state of resources. If you call PUT methods N times, the first request updates the resource and the subsequent requests will be overwriting the same resource again and again without changing anything. Hence, PUT methods are idempotent.
    • DELETE methods are said to be idempotent because when calling them for N times, the first request results in successful deletion (Status Code 200), and the next subsequent requests result in nothing – Status Code 204. The response is different, but there is no change of resources on the server-side.
      • However, if you are attempting to delete the resource present, at last, every time you hit the API, such as the request DELETE /user/last which deletes the last user record, then calling the request N times would delete N resources on the server. This does not make DELETE idempotent. In such cases, as part of good practices, it is advisable to use POST requests.