[firebase_storage] uploading lots of files concurrently causes major app lag

[jamesdixon]

Hello!

We have an app that allows a user to upload files as part of a report. In many cases, our users have no/poor cell service. We've been doing some testing in these scenarios. To start, we've used airplane mode to disconnect the network completely and then will take approx 100 or more photos (and a few videos). When we disable airplane mode and the network comes online, the files resume upload as expected. However, it causes SIGNIFICANT lag across the entire app and only clears up when these uploads are complete.

My first guess was that these uploads aren't truly done in the background and because of that, are causing a lot of work on the UI thread. I do realize there may be other forces at play here but I was hoping someone might be able to tell me how Firebase Storage handles these uploads. Are they on a separate thread?