Progress reporting for large file downloads doesn't work well

[sjchristi]

Is this a bug report, a feature request, or a question?

bug report / question

We've had an issue where some users are telling us download aren't working. Some of the downloads in our app are quite large (> 1 GB). I looked into it, and it looks like it's caused by the progress callback not being triggered.

If you look at this code here:

react-native-background-downloader/ios/RNBackgroundDownloader.m

Line 454 in ffca4f8

if ([percent floatValue] - [prevPercent floatValue] > 0.01f) {

You will see a progress callback is only made if at least 1% of the progress has changed. But, for huge files, for example 1GB, that 1% is 10 megabytes. If a user is on a slow connection, that means they can be going 30 seconds+ without any sort of progress callback, which makes the user think the download is broken.

I'm going to create a fix for this issue, but was hoping that I could get some feedback @kesha-antonov

I had a couple ideas:

• add a variable to control the max time between progress updates. If that time has elapsed and we haven't had a progress callback, then make the callback (was thinking I'd put this at ~10 seconds).
• change the progress callback to not use percentage of file, but to also use some minimum size as well.. So for example, trigger the callback if > 1% of the progress has changed, OR there has been more than 1MB downloaded since last progress report

Any suggestions? Or other ideas? Would like to hear your ideas.

thanks,
Sam