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alanmcgovern / monotorrent

The official repository for MonoTorrent, a bittorrent library for .NET
https://github.com/alanmcgovern/monotorrent
MIT License
1.15k stars 397 forks source link

Download Speed Gradually Drops to 0 #698

Open kaedei opened 2 months ago

kaedei commented 2 months ago

In the latest version, if multiple download tasks (e.g., >5) are added simultaneously, the download speed for all tasks gradually drops to 0 after some time. This often happens after the first task is completed or when the remaining tasks are about 50% done.

I reviewed the recently updated code but haven't pinpointed the exact location or possible cause of the issue.

I tried rolling back the repository to versions from September 11, 2024, September 7, 2024, August 30, 2024, August 19, 2024, and August 10, 2024. I found that the batch download function works normally without the speed dropping to 0 only when I rolled back to the August 10, 2024 version (f9b120fe929353f5a27868dc4c38aac02c4b1434).

I looked through the nearby commits and suspect that https://github.com/alanmcgovern/monotorrent/commit/9a6db98878b74f26092f6ebd8940d914e3549a95 might be causing the issue, but I couldn't identify any problems in the code and am not sure if this judgment is correct.

alanmcgovern commented 2 months ago

Interesting!

Out of curiosity, do you have logs from one of these sessions which indicates which messages were being sent when the connection was (eventually) dropped? If not, can you share one or two of the torrents where this is happening? Perhaps there's an edge case which I haven't hit yet which is causing one piece to be undownloadable, or repeatedly fail hash checks.

alanmcgovern commented 2 months ago

@kaedei Also, could you try with the pre-release 3.0.3-alpha.unstable.rev0049 version in case that resolves the issue? I think i made a few more changes to upgradeable connections since that suspect commit landed after I identified some issues, so perhaps you're experiencing one of those?

kaedei commented 1 month ago

@kaedei Also, could you try with the pre-release 3.0.3-alpha.unstable.rev0049 version in case that resolves the issue? I think i made a few more changes to upgradeable connections since that suspect commit landed after I identified some issues, so perhaps you're experiencing one of those?

Thank you for the reminder. I created a demo project and tried using the latest version of the nuget package 3.0.3-alpha.unstable.rev0049 to download multiple torrent tasks. The code is available at: https://github.com/kaedei/monotorrent-303-speed-test

I found that the issue seems to be related to the .NET version I am using. I created two Console App projects with .NET 8 and .NET framework 4.6.2, using the exact same test code and referencing the latest monotorrent. It turns out that the MonoTorrent in the .NET 8 version is very fast and has no issues, while the .NET 4.6.2 App takes a long time to start downloading and is very slow.

Could this difference be the reason for the slow download speed?

alanmcgovern commented 1 month ago

Hrm, that's interesting. It'd imply there's a bug or issue in one of the backwards compatibility fallbacks for older .net versions (probably!). I'll give that a shot. I rarely use with .net472 version myself and rely on the testsuite to catch issues.