Easy way to handle nested transactions

Question

Suppose there is an "addUser" function, inside we need to insert a record to "Account" table and "User" table, so the two steps have to be within a transaction too, so we will write the following code:

function addUser (userName, password) {
    sequelize.transaction(function () {
        return AccountModel.create(...)
        .then(UserModel.create(...))    
    })
}

However, in another "addTeam" function, inside we need to insert a record to "Team" table and create a admin user using the above function. The function also need to be wrapped inside a transaction.

So the problem comes, the "addUser" function sometimes need to begin a new transaction, and sometimes need to use the transaction passed in. The most obvious ways is below:

function addUser (userName, password, transaction) {
       let func = function (t) {
           return  AccountModel.create(..., t)
           .then(()=>UserModel.create(..., t)));
       if (transaction) func(t);
       else sequelize.transaction(x=>func(t));
}

function addTeam() {
     sequelize.transaction(x=> {
         TeamModel.create(..., x)
         .then(y=>addUser(x));
     });
}

Obviously, it is awful. How to deal with it easily, which let transaction totally transparent to the caller like below:

@Transaction
async function addUser(userName, password) {
    await AccountModel.create(...);
    await UserModel.create(...);
}

@Transaction
async function addTeam(...) {
    await TeamModel.create(...);
    await addUser(...);
} 

Answer 1

sequelize.transaction accepts an options object - If options.transaction is set, this will create a savepoint in the transaction (provided that the SQL dialects supports it), otherwise it will create a new transaction

http://docs.sequelizejs.com/en/latest/api/sequelize/#transactionoptions-promise

So you should be able to do simply

sequelize.transaction({ transaction }, x=>func(t));

Answer 2

If you use CLS, a very simple helper function will do the work.

const cls = require('continuation-local-storage');
const Sequelize = require('sequelize');
const NAMESPACE = 'your-namespace';

// Use CLS for Sequelize
Sequelize.cls = cls.createNamespace(NAMESPACE);
const sequelize = new Sequelize(...);

/* * * * * * * * * * * * * * * * * * * * *
 * THE MAGIC: Create a transaction wrapper
 * * * * * * * * * * * * * * * * * * * * */

function transaction(task) {
  return cls.getNamespace(NAMESPACE).get('transaction') ? task() : sequelize.transaction(task);
};

/* * * * * * * * * * * * * * * * * * * * *
 * Your code below
 * * * * * * * * * * * * * * * * * * * * */

function addUser(userName, password) {
  return transaction(function() {
    return AccountModel
      .create(...)
      .then(() => UserModel.create(...));
  });
}

function addTeam() {
  return transaction(function() {
    return TeamModel
      .create(...)
      .then(() => addUser(...));
  });
}