Node.js 7 how to use sequelize transaction with async / await?

Question

Node.js 7 and up already support async/await syntax. How should I use async/await with sequelize transactions?

Answer 1

The accepted answer is an "unmanaged transaction", which requires you to call commit and rollback explicitly. For anyone who wants a "managed transaction", this is what it would look like:

try {
    // Result is whatever you returned inside the transaction
    let result = await sequelize.transaction( async (t) => {
        // step 1
        await Model.destroy({where: {id: id}, transaction: t});

        // step 2
        return await Model.create({}, {transaction: t});
    });

    // In this case, an instance of Model
    console.log(result);
} catch (err) {
    // Rollback transaction if any errors were encountered
    console.log(err);
}

To rollback, just throw an error inside the transaction function:

try {
    // Result is whatever you returned inside the transaction
    let result = await sequelize.transaction( async (t) => {
        // step 1
        await Model.destroy({where: {id:id}, transaction: t});

        // Cause rollback
        if( false ){
            throw new Error('Rollback initiated');
        }

        // step 2
        return await Model.create({}, {transaction: t});
    });

    // In this case, an instance of Model
    console.log(result);
} catch (err) {
    // Rollback transaction if any errors were encountered
    console.log(err);
}

If any code that throws an error inside the transaction block, the rollback is automatically triggered.