Node js: How to handler multiple request in one API

user_8175074 0
Viewed 46

Let say this is my API:

app.post('/refund', function (req, res) {
        Transaction.findOneAndUpdate({_id: req.body.transaction_id}, {$set: {refund_status: true}}).
        exec(function (err, transaction_status) {
            res.end("Refund successfully")
        }
}

If two admins click the refund button at the same time. My customer will receive a double refund.

So, how to prevent these issues?

node.js mongodb
2 Answers

Simply get the transaction first and check the refund status and update. If its false refund. If its true tell its already refunded.

  app.post('/refund', function (req, res) {
    // get the transaction first
    Transaction.find({_id: req.body.transaction_id}, function(err, doc) {
      if (doc.refund_status == false) {
         Transaction.findOneAndUpdate({_id: req.body.transaction_id}, {$set: {refund_status: true}}).exec(function(err, transaction_status) {
           res.end("Refund successfully")
      })
      } else { // already refunded
        res.end("Already refunded")
      }
     })
  }
user_43717670

Implement your refund logic in a callback from session.withTransaction(). That will prevent concurrent updates. Don't worry about the async stuff; .withTransaction() handles it correctly.

Or, make your refund logic idempotent. That is, implement it in a way that calling it multiple times does exactly the same thing as calling it once. Your setup is almost idempotent as it is: you start with the transaction id and set its refund statuse to true. But the idempotence may not work for you if you must report when the transaction is already refunded.

user_2056080
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