This weekend, I was bogged down with concurrency related problems with ApnaBill.com – all of which were solved with the 62nd svn commit.

Different scenarios which we thought could have been possible

• User A and User B both attack the same coupon at same time
• User B tries to lock a coupon which was previously locked by User A
• User A tries to lock multiple coupons at time – knowingly!
• User A accidentally locks multiple coupons at a time

More problems arise specially when you have no control over the payment gateway pages (ie. when you are using a redirect to a payment gateway).

• When does the timeout occurs
• What happens if a timeout occurs
• What if the transaction was _killed_ midway
• How to deal with timeouts and locking/unlocking mechanism, etc

The newest addition to ApnaBill.com code in the payment gateway interaction arsenal

Luckily, almost all problems were solved for ApnaBill – All we expect from the user is to follow what’s shown on screen. Even otherwise, he should be good! For everything else – as they say – is the dear support staff

Like that alert box? Try http://www.bioneural.net/2006/04/01/create-a-valid-css-alert-message/

Hmm, I think, we should profile all the user displayable messages before we launch. I want to make sure that all have the same tone.

PS: Me and Sandy have never brainstormed more on any other issue than concurrency handling.

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