[SOLVED] Incomplete/Incorrect Download reported as completed

[Sodomy]

For a few times now starting with 1.9 on 10.5.8, I've noticed that some of the mp3s in a torrent I downloaded have very bad skips on them. After a bit of investigation, I found out the problem was Transmission. Even though those torrents were reported as completed, progress bar green, when I highlight the torrent and do a "Verify Local Data", the bar went from green to yellow, and it'd resume downloading the last bits it needs. At that point, the mp3 finally stop skipping. It's gotten to the point where I have to do a "verify local data" on every torrent that supposedly finished downloading. And so far, I'd say about half the music torrents I download aren't actually complete and have to download a bit more. I've downloaded thousands of torrents on Transmission before, this has never been a problem until now. And apparently, I'm not the only one having the problem. Someone else complained to me that a torrent I upped had skips in it, I noticed he was on Transmission 1.91 and I told him to do a verify local data. His reply:

You nailed it. I was definitely missing a good 3MB. I have seen transmission download pieces of torrents I had already downloaded in the past when I resumed transmission after a reboot, but didn't think anything of it... This is very disconcerting. Makes me want to switch to rtorrent, but rtorrent takes forever and a day to re-verify its data after a restart, and doesn't save its own copy of the torrent files you give it, like transmission so nicely does. Not sure what to do in the meantime. heh.

Please to fix.

[dhl]

I just had this happen to me as well. Transmission indicated a full download but Verify Local Data found one piece missing, instantly downloaded it and the problem was solved. I don't want to have to manually verify every download but I can't trust the current version with this bug. I've rolled back to 1.83 for the time being.

Developers, please take note for the next release!

[holyholyholy]

I've been getting this too, went back to 1.83. Super super annoying.

[Jordan]

Does anyone have a URL for a public, small torrent file showing this behavior?

[Jordan]

Okay, after downloading a specific single file again... and again... and again... and again... I've finally found a pattern:

In the swarm that was emailed to me, there's at least one Bad peer constantly sending bad blocks out to everyone. During endgame, Transmission can double-request a block from two peers. (This isn't the problem... all clients do this. If you're new to this idea, go Google "endgame") If one of those peers is the Bad peer, and if the good peer's block comes in first and if that block completes the piece, then we checksum the piece and mark it as good. Then when the bad peer sends in its bad version of the block, we wrongly save it too, instead of throwing it away. And since the piece is already flagged as complete, we don't re-checksum it.

I've committed a fix for this behavior to trunk in r10325. I think it's "the" fix and ran 10 trials after making the change, and can no longer trigger the corruption bug.

Since so many "ifs" were required to tickle this bug in the first place, I'd be happy if other people could test it out to try and confirm the fix by running a nightly build of r10325 or higher from http://transmission.xpjets.com/ .

Also I find the comment of "just try any file" pretty boggling... I'm not seeing this happen except for in those really specific circumstances.

Xref: http://trac.transmissionbt.com/ticket/1242

[Sodomy]

Does this fix help me avoid the crash via the comparePieceByWeight assertion fail as I reported here: http://forum.transmissionbt.com/viewtop ... f=4&t=9692 ?

Otherwise, I'm reluctant to test it out, as it is exactly downloads that trigger the crash, and Transmission takes hours to get the announces done each time I restart.

[Jordan]

Does this fix help me avoid the crash via the comparePieceByWeight assertion fail as I reported here: http://forum.transmissionbt.com/viewtop ... f=4&t=9692 ?

Otherwise, I'm reluctant to test it out, as it is exactly downloads that trigger the crash, and Transmission takes hours to get the announces done each time I restart.

Yes, that's fixed in the nightlies.

[Sodomy]

\o/ I go try out now. I kiss you!

[Sodomy]

Haven't had a relapse since the nightly builds that promised to fix it. Looking good!