How to Use MongoDB Transactions in Node.js

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async function createReservation(client, userEmail, nameOfListing, reservationDates, reservationDetails) {
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}

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const usersCollection = client.db("sample_airbnb").collection("users");
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const listingsAndReviewsCollection = client.db("sample_airbnb").collection("listingsAndReviews");

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const reservation = createReservationDocument(nameOfListing, reservationDates, reservationDetails);

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const session = client.startSession();

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const transactionOptions = {
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    readPreference: 'primary',
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    readConcern: { level: 'local' },
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    writeConcern: { w: 'majority' }
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};

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try {
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} catch(e){
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} finally {
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}

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const transactionResults = await session.withTransaction(async () => {}, transactionOptions);

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const usersUpdateResults = await usersCollection.updateOne(
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    { email: userEmail },
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    { $addToSet: { reservations: reservation } },
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    { session });
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console.log(`${usersUpdateResults.matchedCount} document(s) found in the users collection with the email address ${userEmail}.`);
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console.log(`${usersUpdateResults.modifiedCount} document(s) was/were updated to include the reservation.`);

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const isListingReservedResults = await listingsAndReviewsCollection.findOne(
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    { name: nameOfListing, datesReserved: { $in: reservationDates } },
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    { session });
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if (isListingReservedResults) {
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    await session.abortTransaction();
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    console.error("This listing is already reserved for at least one of the given dates. The reservation could not be created.");
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    console.error("Any operations that already occurred as part of this transaction will be rolled back.");
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    return;
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}

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const listingsAndReviewsUpdateResults = await listingsAndReviewsCollection.updateOne(
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    { name: nameOfListing },
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    { $addToSet: { datesReserved: { $each: reservationDates } } },
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    { session });
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console.log(`${listingsAndReviewsUpdateResults.matchedCount} document(s) found in the listingsAndReviews collection with the name ${nameOfListing}.`);
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console.log(`${listingsAndReviewsUpdateResults.modifiedCount} document(s) was/were updated to include the reservation dates.`);

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if (transactionResults) {
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    console.log("The reservation was successfully created.");
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} else {
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    console.log("The transaction was intentionally aborted.");
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}

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console.log("The transaction was aborted due to an unexpected error: " + e);

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await session.endSession();

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async function createReservation(client, userEmail, nameOfListing, reservationDates, reservationDetails) {
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    const usersCollection = client.db("sample_airbnb").collection("users");
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    const listingsAndReviewsCollection = client.db("sample_airbnb").collection("listingsAndReviews");
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    const reservation = createReservationDocument(nameOfListing, reservationDates, reservationDetails);
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    const session = client.startSession();
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    const transactionOptions = {
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        readPreference: 'primary',
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        readConcern: { level: 'local' },
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        writeConcern: { w: 'majority' }
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    };
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    try {
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        const transactionResults = await session.withTransaction(async () => {
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            const usersUpdateResults = await usersCollection.updateOne(
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                { email: userEmail },
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                { $addToSet: { reservations: reservation } },
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                { session });
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            console.log(`${usersUpdateResults.matchedCount} document(s) found in the users collection with the email address ${userEmail}.`);
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            console.log(`${usersUpdateResults.modifiedCount} document(s) was/were updated to include the reservation.`);
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            const isListingReservedResults = await listingsAndReviewsCollection.findOne(
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                { name: nameOfListing, datesReserved: { $in: reservationDates } },
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                { session });
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            if (isListingReservedResults) {
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                await session.abortTransaction();
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                console.error("This listing is already reserved for at least one of the given dates. The reservation could not be created.");
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                console.error("Any operations that already occurred as part of this transaction will be rolled back.");
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                return;
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            }
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            const listingsAndReviewsUpdateResults = await listingsAndReviewsCollection.updateOne(
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                { name: nameOfListing },
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                { $addToSet: { datesReserved: { $each: reservationDates } } },
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                { session });
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            console.log(`${listingsAndReviewsUpdateResults.matchedCount} document(s) found in the listingsAndReviews collection with the name ${nameOfListing}.`);
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            console.log(`${listingsAndReviewsUpdateResults.modifiedCount} document(s) was/were updated to include the reservation dates.`);
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        }, transactionOptions);
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        if (transactionResults) {
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            console.log("The reservation was successfully created.");
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        } else {
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            console.log("The transaction was intentionally aborted.");
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        }
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    } catch(e){
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        console.log("The transaction was aborted due to an unexpected error: " + e);
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    } finally {
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        await session.endSession();
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    }
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}

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await createReservation(client,
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    "leslie@example.com",
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    "Infinite Views",
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    [new Date("2019-12-31"), new Date("2020-01-01")],
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    { pricePerNight: 180, specialRequests: "Late checkout", breakfastIncluded: true });

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1 document(s) found in the users collection with the email address leslie@example.com.
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1 document(s) was/were updated to include the reservation.
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1 document(s) found in the listingsAndReviews collection with the name Infinite Views.
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1 document(s) was/were updated to include the reservation dates.
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The reservation was successfully created.

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{
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"_id": {"$oid":"5dd68bd03712fe11bebfab0c"},
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"email": "leslie@example.com",
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"name": "Leslie Yepp",
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"reservations": [
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    {
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    "name": "Infinite Views", 
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    "dates": [
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        {"$date": {"$numberLong":"1577750400000"}},
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        {"$date": {"$numberLong":"1577836800000"}}
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        ],
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    "pricePerNight": {"$numberInt":"180"},
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    "specialRequests": "Late checkout",
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    "breakfastIncluded": true
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    }
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]
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}

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{
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"_id": {"$oid": "5dbc20f942073d6d4dabd730"},
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"name": "Infinite Views",
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"summary": "Modern home with infinite views from the infinity pool",
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"property_type": "House",
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"bedrooms": {"$numberInt":"6"},
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"bathrooms": {"$numberDouble":"4.5"},
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"beds": {"$numberInt":"8"},
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"datesReserved": [
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    {"$date": {"$numberLong": "1577750400000"}},
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    {"$date": {"$numberLong": "1577836800000"}}
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]
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}