Top comments(8)
- LocationStuttgart, Germany
- EducationComputer Science and Media
- WorkI wrote "React From Zero" at \newline
- Joined
Idempotency just means, calling the same function/endpoint multiple times, with the same arguments, will result in the same state.
if you write an endpoint like/player/increaseScoreByOne it will change the state as often as you call it.
if you write an endpoint like/player/setScoreTo?value=100 it will always result in the same state.
When your request doesn't get through, you can safely make it again without worrying about an inconsistent server state.
Not for 5 year olds, but I hope it helps xD
- WorkJunior Java Developer with 5+ Years of Professional experience
- Joined
First of all, thank you for answering.
Considering your reply,
Idempotent: GET, TRACE, OPTIONS
Non-Idempotent: DELETE
Where do I place DELETE and PUT, and why?
- LocationStuttgart, Germany
- EducationComputer Science and Media
- WorkI wrote "React From Zero" at \newline
- Joined
You have to think aboutone action when thinking about idempotency.
If you callDELETE 100 times, it will still be the same item that is deleted, you remove it from memory, the DB or set a fielddeleted = true or something. Same goes forPUT, you send an update to the server, but you "set" state to a new state,you don't do stuff like "increase value x", "append string to y" or "subtract 10 from z".
Sure the data will be gone for your nextGET request if you issued 1 or 100DELETEs, but the idea is that the 100DELETEs end in the same state as the 1DELETEs
- WorkJunior Java Developer with 5+ Years of Professional experience
- Joined
Gotcha!! Thanks buddy :)
- LocationSeattle, WA
- EducationComputer Science
- WorkVP of Engineering at DreamBox Learning
- Joined
The 5-year-old explanation could be:
You can go to your parents and ask the same thing, in the same way, any number of times.
If nothing else changes, the act of asking something over and over will not change the answer. They won't even get annoyed.
:)
- LocationAntwerp
- Joined
Very nice metaphor. Perhaps a small addition: You can go to your parents and ask the same thing, in the same way, any number of times. If you’re sure they were listeningat least once, then you can be sure that they will take care of whatever it is you asked.
Notably, the samemight also be true for non-idempotent verbs; the difference is that there you don’t have theguarantee that it will always behave idempotently.
A great example of an idempotent function is the absolute value function.abs(-4) = 4abs(4) = 4. Continuing to applyabs() onto itself will always yield the same result.
For those that have done some Elixir before:-4 |> abs |> abs |> ... will always yield4
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