CODEWITHSUNDEEP
node.jsmongodbmongoose
Alexander Mills
Alexander Mills

Reputation: 100080

Create atomic stored procedure / "stored JS" with MongoDB

We need to create an atomic routine in our MongoDB database.

We need to iterate through a collection, find the highest number given a field from all documents in the collection, then increment it. We are working with some legacy data that we need to integrate, otherwise we'd have some atomic sequence already in place.

How can I create stored JS or a stored procedure in MongoDB that can run a whole routine atomically?

I am seeing some information but nothing is looking particularly clear to me:

Called a stored javascript function from Mongoose?

https://groups.google.com/forum/#!topic/mongoose-orm/sPN3wfDstX4

https://github.com/mongoosejs/mongoose-function

Where can I find good information how to actually write an atomic/blocking stored procedure that runs in MongoDB, and how to actually invoke the stored procedure from the application?

Upvotes: 0

Views: 208

Answers (1)

Sergio Tulentsev
Sergio Tulentsev

Reputation: 230376

(summarizing the comments above)

At the moment, there is nothing in mongodb that will allow you to run a piece of arbitrary logic (including, for example, multiple queries to gather data) atomically.

The best atomic thing that mongodb has to offer is findAndModify. Its atomicity is naturally restricted to only one document and you have a pretty limited list of update operators (that is, you can't even use the fields of the document, same as regular updates).

It is somewhat possible using an application-level lock: the application inserts or modifies a special lock document, which will signal to other parts of the application "I'm using/updating this, please refrain from touching it". After the operation is completed, application releases the lock, so it's now free to be re-acquired by someone else. Of course, this relies entirely on actors respecting the lock agreements, which is not very reliable, to put it mildly.

Upvotes: 1

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