ASP.Net web service synchronize call to process database queue

Question

I have an asp.net web service which is like a reservation system and cannot reserve the same seat by multiple persons and the eligibility for the reservation is based on some other table values in SQL server. I plan to use SQL server queue processing as mentioned here . My customer wants to do this in a synchronized call, means we want the result in the same web service method call. My question is how efficient it to allow a synchronized method call to process a queue and wait until the queue return values (by means of a loop within a time span or so). Please advise the best possible approaches to achieve this.

Answer 1

You are stepping in the XY problem trap . Your primary goal is to make sure no seat can be reserved twice. You should rethink your approach of using a queue is the appropriate solution to this problem. A queue is great to efficiently use your processing resources on a background task. For real-time processing (like yours) it will create more problems that it solves.

It seems like you want to avoid the race condition that occurs when multiple users try to access the same seat twice. The queue doesn't solve the problem, you just move it to the enqueing phase. The one who enters the queue first wins. At the end you have added an unnecessary complication that doesn't bring you any benefit.

A much simpler solution to your problem is to create a unique key on your DB that makes sure that no seat can be reserved twice. Once you try to reserve a seat that has been taken just a moment ago, you will get an SQLException with the error number 2627 . You can then prompt the user that the seat is taken.