I'm working on a web application as a front end for an Excel Sheet. The REST-APIs seems to be quiet clear. But I am not sure how to handle concurrency correctly. I want to avoid that two clients accidentally override their data. I need some kind of primary key which could be edited in worst case by two users. What is the correct way to handle that with the Microsoft Graph?

Right now I have in mind to do some kind of double locking so that I allocate a key and check then if it was overwritten after a second. But that seems to be quiet hacky and I'm sure that there is a way to lock cells so that two users cannot edit the same cells.

CodePudding user response：

Normally you do this with ETag and update only when the If-Match header is verified. When somebody changes the resource, then the ETag changes and the old ETag won't match any longer. There can be still a short period of time when the ETag is the old for both requests, so there is no perfect solution.

In the case of MS Graph API I see an "@odata.etag" property for the resource and the sub-resources, so I assume they use it for this and maybe the send the ETag header for the actual resource too. At least it works this way for this MS WebAPI, so if this is a different product, then still I think they use the same solution for the Graph API too. https://learn.microsoft.com/en-us/power-apps/developer/data-platform/webapi/perform-conditional-operations-using-web-api#bkmk_DetectIfChanged They might send the ETag header for the actual resource too.