Can't upload more than 5 files from dropbox

[pdpinch]

Steps to Reproduce

1. Create a new collection
2. Upload the 32 videos from https://www.dropbox.com/sh/27n8kzccjxv7dm1/AADn0oY1V2gjjZXkbuP8gu_Sa?dl=0

Expected Behavior

• All 32 videos get queued for transcode

Actual Behavior

• Only 5 videos got queued
• I have to reload the page to see what's been queued

[pdpinch]

The number of videos that get queued seems to be variable. On a subsequent attempt, I uploaded 16 and 7 were queued.

[pdpinch]

No apparent errors in Sentry, but when I watch in my browser, I see a 504 response from https://video.odl.mit.edu/api/v0/upload_videos/

[mbertrand]

I think the celery task to stream videos to S3 and start transcoding jobs is not running asynchronously:

        # Kick off chained async celery tasks to transfer file to S3, then start a transcode job
        task_result = chain(
            tasks.stream_to_s3.s(video.id), tasks.transcode_from_s3.si(video.id)
        )()

The () at the end should probably be replaced with .apply_async()

[pdpinch]

@collinpreston @mbertrand do you think we can close this?

[mbertrand]

I think so, it seems to be working well now

[collinpreston]

Passed testing again today. Closing.