490305 - download manager UI blocks the real download progress

Status: UNCONFIRMED

(Toolkit :: Downloads API, defect)

Description

[yingyi.liang]

User-Agent:       Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10_5_6; en-us) AppleWebKit/528.16 (KHTML, like Gecko) Version/4.0 Safari/528.16
Build Identifier: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.0.8) Gecko/2009032711 Ubuntu/8.04 (hardy) Firefox/3.0.8

When downloading a huge file, the back-end download process is blocked by the download manager UI until the UI finishes its update. This is probably because the back-end uses synchronous RPC to update the UI display.


Reproducible: Always

Steps to Reproduce:
1. have two hosts, with one located in a high-speed network (e.g. corporate/university network), the other located in a DSL network (e.g. a home computer); let's denote the first one as A and the second one as B; 
2. from host B, remote-login to host A via "ssh -X" and start firefox on A; this will make the back-end run on A but the front-end rendered on B;
3. download a huge file (e.g. a vm image from the vmware appliance market);
4. when the download manager UI is being displayed, the download speed will quickly slow down to the DSL speed; this speed can be shown to be real by monitoring the partial downloaded file on A.
5. close the download manager window; monitor the partial downloaded file on A to see the download speed goes up immediately.
Actual Results:  
The download speed is decided by the host running the front-end, not the one running the back-end.

Expected Results:  
The download speed should be decided by the back-end host.