[tahoe-dev] new-downloader pushed!

[Brian Warner]

I just finished pushing the new-downloader (#798) code into trunk. This
represents about 6 months of persistent effort: it's a great relief to
finally get it published.

I'll start working on the bugs that Francois found (#1154, #1155)
tomorrow, hopefully I can get them fixed in a day or two.

Please grab trunk and bang on it! I believe the code should be as least
as functional as the old downloader. In addition, it should handle
servers disconnecting during download much better (as long as those
disconnects are obvious; silent disconnects will still cause a long
stall, just like before). The main thing that it might handle worse is
when shares are doubled up: I think the new downloader may tend to pull
multiple shares from a single server more frequently than the old one
did. Both issues are things I hope to fix soon, but I don't know if
they'll make the cut for 1.8 (seeing as how 1.8 was supposed to be
frozen and entering beta a week ago).

The new downloader *will* handle silent-disconnects during the initial
do-you-have-share query, by looking elsewhere after 10 seconds of
unresponsiveness. I also expect it should download small files a lot
faster (by making fewer roundtrips), but I haven't done any benchmarks
to find out. It needs a non-ancient storage server (1.3.0 or newer, with
the "tolerate-overrun" feature) to achieve top speed, but will work
correctly with older ones too.

Please let me know how it works!

cheers,
 -Brian