Transaction_management NPM

Transaction Management

Links

How to Define a Transaction

Each transaction must succeed or fail as a complete unit. A transaction can never be partially complete. A transaction is written as a generator function *placeOrder() which in turn yields a sequence of transaction processes such as calculateTotal(orderId), updateCouponUsage(couponNumber), chargeVendorFee(), chargeCreditCard(ccNumber), and saveOrder(orderId).

How to Define a Transaction Process

Each transaction process is written as a function returning an object including three methods execute(), retry(), rollback(), and an object retryPolicy{}.

Both execute() and retry() are provided a boolean argument in which true indicates that this attempt is the last possible attempt, or false if there are retries remaining.

Both execute() and retry() will return a boolean in which true indicates success and false indicates failure.

The object retryPolicy{} includes the numeric variable numRetries with a non-negative integer value of 0 or more. The transaction processes are executed sequentially and all retries attempted until the policy is exhausted. If the retry policy is exhausted, all transaction processes that had been successfully completed will have their rollback() method called in reverse sequence.

The executeTransaction() method returns a boolean value in which true indicates success of the whole transaction and false indicates that the whole transaction had failed. In the case of false, any individual transaction process that had succeeded will have also been rolled back.

Installation

npm install transaction_management --save

Usage

var transact = require('transaction_management');

transact.executeTransaction( placeOrder() );

function *placeOrder() {
  yield transact.calculateTotal(orderId);
  yield transact.updateCoupon(couponNumber);
  yield transact.chargeVendorFee();
  yield transact.chargeCreditCard(ccNumber);
  yield transact.saveOrder(orderId);
}

//=>

Attempting to calculate total for order ${orderId}... Failed/Succeeded.
Attempting to update coupon ${couponNumber}... Failed/Succeeded.
Attempting to charge vendor fee... Failed/Succeeded.
Charging credit card with ccNumber ${ccNumber}... Failed/Succeeded.
Saving order ${orderId}... Failed/Succeeded.
Rolled back credit card charge for ${ccNumber}.
Rolled back vendor charge.
Rolled back coupon ${couponNumber} update.
Rolled back order ${orderId} total calculation.