Show HN: Rapel – chunked resumable downloads in unstable networks

by autorun • 2 months ago

21 9 2 months ago

Cool. After reading your README, the "post-part" hook is the most interesting part for me. Chunk-level hooks make it easier to plug into things like rclone or other workflows. As you mentioned, the single .rapel-state.json file tracks all chunk metadata. Does that state also pin the origin file identity while resuming, so it can detect if the remote file changed between sessions?

autorun2• 2 months ago

Thanks for pointing it out, README is outdated, .rapel-state.json is not being used anymore, as the current state is now calculated from the chunk files downloaded. It doesn't detect remote file changes.

pcchristie• 2 months ago

Is this like a modern GetRight?

GetRight is possibly the piece of software that planted the seed of fascination with computers and software in my head at a young age. It blew my mind that someone had made an app that could fix Internet Explorer dropping downloads mid-way through on my dial-up connection if my Nanna sent a fax to my Mum whilst I was on the PC.

8cvor6j844qw_d6• 2 months ago

Same, I think I went with Flashget.

I seem to recall that I'm fascinated with NetAnts too, but went with Flashget for some reason.

a_t48• 2 months ago

A little bit of a nit - when tracking progress you can ditch the mutex by using atomic integers for the download progress. Instead of using locks, your test for a chunk being done becomes something like "downloaded == chunk_size".

You also never call UpdateChunkProgress, FYI! The code is a little confusing to read because of that dead variable, at first I thought that chunks are never resumed. ProgressTracker and State/ChunkInfo do similar things, if I were in your shoes I'd make it so that there's clear ownership over where progress is actually tracked.

...I'd probably move State to be saved on the _start_ of the download, have it solely be responsible for tracking the arguments that the download was called with. Rename it to DownloadArguments, delete all the runtime state tracking, as it's already inferred by the downloader on start.

hackingonempty• 2 months ago

Looks like fun but also a half implemented BitTorrent client.

d3Xt3r• 2 months ago

How is this any different than existing solutions like aria2? I'd also like to see some benchmarks for the same download using the same chunk size settings with Rapel vs aria2.

autorun2• 2 months ago

I tried using existing solutions like aria2, but rapel is built to work on constrained machines with limited storage, like a raspberry pi running 24/7. You can use the post-part argument so that after downloading a chunk, you can do something with it (eg. upload it) and remove it afterward. Then, on another bigger machine, download the chunks and merge them

amjadfatmi1• 2 months ago

Very interesting, Curious how does it handles concurrency especially in mass at scale in production

Show HN: Rapel – chunked resumable downloads in unstable networks

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