트랜잭션

{ _id: 98765, orders: [] }

[
 { name: "sunblock", sku: 5432, qty: 85 },
 { name: "beach towel", sku: 7865, qty: 41 }
]

const cart = [
  { name: 'sunblock', sku: 5432, qty: 1, price: 5.19 },
  { name: 'beach towel', sku: 7865, qty: 2, price: 15.99 }
];
const payment = { customer: 98765, total: 37.17 };

1
async function placeOrder(client, cart, payment) {
2
  const transactionOptions = {
3
    readConcern: { level: 'snapshot' },
4
    writeConcern: { w: 'majority' },
5
    readPreference: 'primary'
6
  };
7
8
  const session = client.startSession();
9
  try {
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    session.startTransaction(transactionOptions);
11
12
    const ordersCollection = client.db('testdb').collection('orders');
13
    const orderResult = await ordersCollection.insertOne(
14
      {
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        customer: payment.customer,
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        items: cart,
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        total: payment.total,
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      },
19
      { session }
20
    );
21
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    const inventoryCollection = client.db('testdb').collection('inventory');
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    for (let i=0; i<cart.length; i++) {
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      const item = cart[i];
25
26
      // Cancel the transaction when you have insufficient inventory
27
      const checkInventory = await inventoryCollection.findOne(
28
        {
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          sku: item.sku,
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          qty: { $gte: item.qty }
31
        },
32
        { session }
33
      )
34
      if (checkInventory === null) {
35
        throw new Error('Insufficient quantity or SKU not found.');
36
      }
37
38
      await inventoryCollection.updateOne(
39
        { sku: item.sku },
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        { $inc: { 'qty': -item.qty }},
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        { session }
42
      );
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    }
44
45
    const customerCollection = client.db('testdb').collection('customers');
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    await customerCollection.updateOne(
47
      { _id: payment.customer },
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      { $push:  { orders: orderResult.insertedId }},
49
      { session }
50
    );
51
    await session.commitTransaction();
52
    console.log('Transaction successfully committed.');
53
54
  } catch (error) {
55
    if (error instanceof MongoError && error.hasErrorLabel('UnknownTransactionCommitResult')) {
56
      // add your logic to retry or handle the error
57
    }
58
    else if (error instanceof MongoError && error.hasErrorLabel('TransientTransactionError')) {
59
      // add your logic to retry or handle the error
60
    } else {
61
      console.log('An error occured in the transaction, performing a data rollback:' + error);
62
    }
63
    await session.abortTransaction();
64
  } finally {
65
    await session.endSession();
66
  }
67
}

const { MongoError, MongoClient } = require('mongodb');