Fetch version metadata in batches

[charliermarsh]

When resolving:

urllib3<1.25.4
boto3

We end up testing hundreds of boto versions. After a point, we should start fetching the version metadata in parallel for these cases.

[konstin]

This is effectively blocked on being smarter with ranges for me, either by being a lot faster with intersections, or ideally having ranges with fewer segments.

Checking the first ~500 version of tf-models-nightly takes 12s for me, which are nearly exclusively spent on range intersection of ranges with a lot of segments, even though we should be able to merge the segments.

[charliermarsh]

Is that with all the metadata cached? The fragmented ranges thing is similar to what @zanieb is looking at for error reporting and is related to an issue I filed on PubGrub about this.

[konstin]

Yes, it basically does not make sense to work on this until pubgrub-rs/pubgrub#135 is fixed or we have some workaround. We could try making intersections really fast but i think this would be effort spent in the wrong place when range shouldn't be that large in the first place.

[konstin]

As an update, pubgrub is much faster now, and it will be even faster for this case with pubgrub-rs/pubgrub#177 (the benchmark i used hits the boto case), so we can retry doing this.