intercept data changes and alter/validate from a server

Question

I'm working on a solution to intercept changes to the data from our node.js server and validate/alter them before they are stored/synced to other clients.

Any strategies or suggestions on how to solve this with the current code base?

Currently, it seems like the only option is to rewrite it post-sync operation. That would mean each client would probably receive the sync (including the server), then the server would rewrite the data and trigger a second sync.

To help understand the context of the question, here's what seems like an ideal strategy for my needs:

• server gets a special token/key not available to clients (when security comes about)
• server registers a dependency injection like firebase.child('widgets').beforeSync(myCallback)
• client syncs data
• server callback is notified
• server modifies or validates the data
• if valid, it returns it to firebase for sync ops
• if invalid, aborts the sync with an error which is returned to the client

Answer 1

Thanks for sharing your ideas!

We've considered this type of approach. You can actually simulate this sort of behavior by structuring your data so that there is an "unvalidated" tree and a "validated" tree.

The "unvalidated" tree would be writeable by the client and the server would monitor it for changes. When a change occurs it would validate the data, and if it passes it would copy it into the "validated" tree which is only writeable by the server. You could pass errors back to the client through Firebase data as well when the validation fails.

This behavior could be packaged into a library that provides the behavior you describe. We may add this as core functionality as well, but we're still researching a variety of options.