javascript - Get Knex.js transactions working with ES7 async/await

Question

I'm trying to couple ES7's async/await with knex.js transactions.

Although I can easily play around with non-transactional code, I'm struggling to get transactions working properly using the aforementioned async/await structure.

I'm using this module to simulate async/await

Here's what I currently have:

Non-transactional version:

works fine but is not transactional

app.js

// assume `db` is a knex instance

app.post("/user", async((req, res) => {
  const data = {
   idUser: 1,
   name: "FooBar"
  }

  try {
    const result = await(user.insert(db, data));
    res.json(result);
  } catch (err) {
    res.status(500).json(err);
  }
}));

user.js

insert: async (function(db, data) {
  // there's no need for this extra call but I'm including it
  // to see example of deeper call stacks if this is answered

  const idUser =  await(this.insertData(db, data));
  return {
    idUser: idUser
  }
}),

insertData: async(function(db, data) {
  // if any of the following 2 fails I should be rolling back

  const id = await(this.setId(db, idCustomer, data));
  const idCustomer = await(this.setData(db, id, data));

  return {
    idCustomer: idCustomer
  }
}),

// DB Functions (wrapped in Promises)

setId: function(db, data) {
  return new Promise(function (resolve, reject) {
    db.insert(data)
    .into("ids")
    .then((result) => resolve(result)
    .catch((err) => reject(err));
  });
},

setData: function(db, id, data) {
  data.id = id;

  return new Promise(function (resolve, reject) {
    db.insert(data)
    .into("customers")
    .then((result) => resolve(result)
    .catch((err) => reject(err));
  });
}

Attempt to make it transactional

user.js

// Start transaction from this call

insert: async (function(db, data) {
 const trx = await(knex.transaction());
 const idCustomer =  await(user.insertData(trx, data));

 return {
    idCustomer: idCustomer
  }
}),

it seems that await(knex.transaction()) returns this error:

[TypeError: container is not a function]

Answer 1

I couldn't find a solid answer for this anywhere (with rollbacks and commits) so here's my solution.

First you need to "Promisify" the knex.transaction function. There are libraries for this, but for a quick example I did this:

const promisify = (fn) => new Promise((resolve, reject) => fn(resolve));

This example creates a blog post and a comment, and rolls back both if there's an error with either.

const trx = await promisify(db.transaction);

try {
  const postId = await trx('blog_posts')
  .insert({ title, body })
  .returning('id'); // returns an array of ids

  const commentId = await trx('comments')
  .insert({ post_id: postId[0], message })
  .returning('id'); 

  await trx.commit();
} catch (e) {
  await trx.rollback();
}