CODEWITHSUNDEEP
firebasegoogle-cloud-firestore
user13775830
user13775830

Reputation:

Do Firebase listeners incur more reads than normal 'snapshots'?

I wonder if firebase listeners incur more reads than 'normal', snapshot gets from firestore database. I assume a listener has to be constantly checking the DB to see if something new is in there and therefore that would add up to the reads on my app.

Upvotes: 1

Views: 1121

Answers (3)

Bumpfel
Bumpfel

Reputation: 101

The whole thing with a listener is that you don't want it to constantly check the database, like on an interval. Instead, a firestore listener opens up a websocket connection which, in contrast to http, allows two way communication - both hosts can be both server and client. This means that instead of constantly checking the database, the server tells you when there are updates, after which your snapshot callback code is run.

So like others has stated, attaching a listener consumes one read per document when the listener is attached, plus one per potential document update for as long as the listener is active.

Upvotes: 1

Marcelo J Forclaz
Marcelo J Forclaz

Reputation: 728

You have two ways to retrieve data from Firestore:

  • Promise
  • Listener

When you make use of promise with get() method, you are sending lazy request to server. While listener method opens a connection channel that retrieve information in real time on every change. (It doesn't mean such a process making request every time)

When you access to data using the Listener strategy, you are opening a communication channel that, of course, consumes connection resources. But you can unsubscribe it: Check How to remove listener for DocumentSnapshot events (Google Cloud FireStore)

Upvotes: 0

Doug Stevenson
Doug Stevenson

Reputation: 317487

A get() is not necessarily more expensive than a snapshot listener. The difference between a get and a listen boils down to the fact that get will read a document exactly once, and a listen will read at least once, which each change to that document incurring another read, for as long as the listener is active.

A listener will only cause more billing for reads if the listener is left active, and the document changes over the time while it's active.

You could instead poll the document with several gets over time, but each one of those gets will cost a document read, even if the document is unchanged. So you will have to determine for yourself what the best way is to get updates to a document, or even if you want updates at all.

Upvotes: 3

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