Verifying data in transmission causes major data loss

[Artem Popov]

Noticed with transmission 1.06 on a fully updated Hardy system.

When there is a download in progress with large large amount of unverified data (marked as yellow), restarting transmission or choosing "Verify local data" from the popup menu makes it discard all the "yellow" (incomplete) pieces causing major data and bandwidth loss.

Reproduced by right-clicking on a torrent with large amount of incomplete (yellow) data and choosing "Verify local data" from the popup menu.

[Chris Jones (cmsj)]

I have observed this on a friend's fresh Hardy install

[Chris Jones (cmsj)]

Attaching the patch that upstream applied to fix this. It doesn't apply entirely cleanly to hardy's Transmission, but with a bit of fuzzing it does.

[Chris Jones (cmsj)]

I have built some test packages with upstream's fix and uploaded them to http://mairukipa.tenshu.net/transmission/

Please could you grab them and test to see if it fixes this issue?

[Charles Kerr (charlesk)]

What that patch tries to do is to change incomplete pieces into complete ones as quickly as possible, before starting on new pieces to download, so that the amount of unverified data is kept to a minimum.

So to test you can't just download the patch and press the "Verify" button... its fix isn't in the verify process but in how & when it downloads pieces.

[Chris Jones (cmsj)]

Hi

charles wrote:
> So to test you can't just download the patch and press the "Verify"
> button... its fix isn't in the verify process but in how & when it
> downloads pieces.

But presumably it could be tested by downloading a whole file and
interrupting the download and manually verifying it?

If there is something fundementally wrong with the fix, that's a
discussion that needs to be had with the upstream developers, I have
simply taken the trac changeset they associated with the upstream bug
and built a package with it :)

--
Chris Jones

[Artem Popov (artfwo)]

Chris, I have installed your packages, but Transmission just stopped working afterwards. It successfully adds torrents, but they remain "idle" forever, and the log is completely silent after "Got scrape response" message.

After I reinstalled the packages from the repository and restarted Transmission, all the files began downloading.

[Chris Jones (cmsj)]

Thanks for the update. I've had someone else test it too and they still saw some dataloss.
I suspect that it's now too late to fix this for Hardy, especially since we don't have a working patch.

[Andrew Starr-Bochicchio (andrewsomething)]

This bug was fixed in the package transmission - 1.32-0ubuntu1

---------------
transmission (1.32-0ubuntu1) intrepid; urgency=low

  * New upstream release. (LP: #256277)
  * debian/control:
   - Add Build-Depends on libnotify-dev.
  * debian/rules, debian/transmission-cli.install, debian/transmission-cli.manpages
   - Remove references to now defunct transmission-proxy.

 -- Andrew Starr-Bochicchio <email address hidden> Sat, 16 Aug 2008 14:02:56 -0400