[tahoe-dev] download optimization?

[Brian Warner]

Jody Harris wrote:
> I haven't seen this addressed in any of the documentation I've looked at:
> 
> Does Tahoe-lafs do any optimization on downloads?
> 
> I'm currently downloading a file that another user on the grid uploaded.
> he then shot me the URI.
> 
> After attaching the URI to a directory listing, I saw that two of the
> shares are on the machine I'm downloading to, and four are on another
> machine within my local network.
> 
> Has any work been done on indexing nodes for "closeness?"

Not yet. Part of the downloader overhaul I want to do for #287 would
include a preference for faster servers (as measured by response time
and how long it takes to download each block). It might also include
some memory of how responsive servers are, so faster ones can be
preferred in the future. And #707 is about intentionally placing some
shares on a local server, which (to be useful) should also change
download to look on the local server first.

We haven't really considered having the node be specifically aware of
network topology on download. #467 and #573 are about server-selection
controls during *upload*, where you might configure your node with a
particular list of servers with topology in mind. But generally they
assume that the download algorithm will remain the same as we have right
now.

It's a good idea though. You'd want it to be somewhat adaptive so that
we still get some load balancing (and not always hammer the local
server, if it's so overloaded that you could actually get the share
faster from someone further away).

cheers,
 -Brian