How to know if inside a transaction with transactionAsyncLocalStorage

[mjanos10]

Is there a way to know if we are inside a transaction when transactionAsyncLocalStorage is enabled?

My use case is that I have three services, A, B and C, where A calls B, and B calls C. But I want to make sure that when B gets called directly (or not from A), it will use a transaction for itself, and service C.

Simplified example:

const AModel = mongoose.model('A', aSchema)
const BModel = mongoose.model('B', bSchema)
const CModel = mongoose.model('C', cSchema)

async function runA() {
  return await mongoose.connection.transaction(async () => {
    const a = await AModel.create({})
    await runB(a)
    return a
  })
}

async function runB(a) {
  // Here it would be great to know if we are in a transaction, so that
  // I could start one if not already in a transaction
  const b = await BModel.create({})
  await runC(b)
  return b
}

async function runC(b) {
  const c = await CModel.create({})
  return c
}

[vkarpov15]

Your best bet would be to access the transactionAsyncLocalStorage directly:

const transactionAsyncLocalStorage = mongoose.transactionAsyncLocalStorage.getStore();
if (transactionAsyncLocalStorage.session && transactionAsyncLocalStorage.session.inTransaction()) {
  // In transaction
} else {
  // not in transaction
}

Does that work for you?

[mjanos10]

That's perfect thank you! I'll take a stab at adding this to the documentation if that's allright with you.

[vkarpov15]

Sure!

[mjanos10]

Hmm actually I don't see the transactionAsyncLocalStorage on mongoose, sorry that I didn't try it sooner. It is also not mentioned in the docs. I'm using mongoose 8.19.1

[vkarpov15]

That's a fair point, transactionAsyncLocalStorage isn't part of our public types. We will look into that. You can put a ts-ignore for now because you'll see transactionAsyncLocalStorage exists at runtime