Eventually I did go through and finish successfully, but I can imagine other people having already closed the tab at that point..

Can you confirm whether you are still seeing this for files <10MB at this time? (It is definitely occurring for very large files >100MB with chunked uploading, probably due to chunk re-assembly taking a while.)

Yes. I just used the old special:upload to upload https://commons.wikimedia.org/wiki/File:WLM-Haifa-wikimania_cc-by-sa.pdf . The UploadWizard got stuck at "finished" and nothing happened for several minutes.

I guess it shows Finished as soon as your browser has sent everything. There will be a delay until the server receives everything and processes it.
So I think this is a UI issue...

Maarten, can you specify whether you set the "Chunked uploading" experimental user preference? Can you reliably reproduce this issue? I am not able to produce it with the same file.

"Chunked uploads for files over 1MB in Upload Wizard" is off.

Adding Roan & Aaron.

I have a very hard time reproducing this; it may be an API issue that only occurs under high server load conditions, or something along those lines. Maarten, in case it's at all browser-related, can you also specify browser/OS version?

afeldman wrote:

If either of the reporters can replicate the scenario whether often or once in a while - can you do so with Chrome's Developer Tools -> Network Panel or Firefox + Firebug's network panel enabled? I'd specifically like to see the timing breakdown for the specific api.php POST containing the file upload - sending vs. waiting.

I'm currently suspicious of a network issue perhaps specific to uploads coming via ESAMS but still gathering data and every bit helps.

Possibly the same as bug 37302 ?

Does this still occur?

Needs an up-to-date report and more details if it's still occurring, closing for now.