Unmanaged transactions, CLS and tests

Good day. This is a duplication of https://github.com/sequelize/sequelize/issues/3888 with some extended examples.

version == 3.4.1

So, here is basic setup:

1. Application, that uses sequelize transactions and create instance of db like:

const createDb = (conf, namespaceName='my-super-personal-namespace') => {
  const {uri} = conf;
  const namespace = cls.createNamespace(cls);

  Sequelize.cls = namespace;

  const options = Object.assign({}, conf); // Sequelize doesn't work with frozen

  const sequelize = new Sequelize(uri, options);
  const Thing = sequelize.import('./thing');

  return {
    sequelize,
    Thing,
    _namespace: namespace
  };
};

1. And here goes a test:

let db;
let transaction;

before(() => {
  db = createDb(config);

  return db.sequelize.sync();
});

beforeEach(() => db.sequelize
    .transaction({autocommit: false})
    .then(t => {
      transaction = t;
    }));

afterEach(() => transaction.rollback());

after(() => db.sequelize.drop());

it('should create instance of Thing', () => {
  return db.Thing.create({
    name: 'foo'
  }, {transaction}).then(thing => {  // FIXME: bad for tests
    expect(thing.id).to.be.a('number');
    expect(thing.name).to.be.eql('foo');
  });
});

This code works but it requires manual pass of transaction.

I’ve expected that following code would work, but it fails in afterEach:

let db;

before(() => {
  db = createDb(config);

  return db.sequelize.sync();
});

beforeEach(() => db.sequelize
  .transaction({autocommit: false})
  .then(t => {
    db._namespace.set('transaction', t);
  }));

afterEach(() => db._namespace.get('transaction').rollback());

after(() => db.sequelize.drop());

it('should create instance of Thing', () => {
  return db.Thing.create({
    name: 'foo'
  }).then(thing => {
    expect(thing.id).to.be.a('number');
    expect(thing.name).to.be.eql('foo');
  });
});

Could you advice please what is a best way to solve this issue?

Thank you!

[janmeier]

If I read your code correctly, this is never going to work with CLS. The transaction is only available in the then callback:

beforeEach(() => db.sequelize
  .transaction({autocommit: false})
  .then(t => {
    db._namespace.set('transaction', t);
    /* ANY FUNCTION CALLED FROM HERE CAN ACCESS t */
  }));

But nothing is done in that callback - after it finished, then context is cleared, because that callback / promise chain ends.

Thing.create should be called from inside the callback:

it('should create instance of Thing', () => {
  return db.sequelize.transaction().then(function (t) {
    db._namespace.set('transaction', t);
    return db.Thing.create({
        name: 'foo'
      }).then(thing => {
        expect(thing.id).to.be.a('number');
        expect(thing.name).to.be.eql('foo');
        return t.rollback();
      });
    });
  });
});

You can also do it slightly more succinctly, by using a managed transaction

return db.sequelize.transaction(function () {
  // No need to call namespace.set here - sequelize takes care of that
});

[akhomchenko]

Update:

My code with CLS can be done like this and it would work, but it is not so ideal.

let db;
let transaction;

before(() => {
  db = createDb(config);

  return db.sequelize.sync();
});

beforeEach(() => db.sequelize
    .transaction({autocommit: false})
    .then(t => {
      transaction = t;
    }));

afterEach(() => transaction.rollback());

after(() => db.sequelize.drop());

it('should create instance of Thing', () => {
  db._namespace.set('transaction', transaction);

  return db.Thing.create({ // Voila, transaction is binded
    name: 'foo'
  }).then(thing => {
    expect(thing.id).to.be.a('number');
    expect(thing.name).to.be.eql('foo');
  });
});