On Thu, Jul 16, 2020 at 10:09 AM George Neuner <gneun...@comcast.net> wrote:
> > On 7/16/2020 4:29 AM, David Storrs wrote: > > The problem seems under-specified. Can you say more about the real > purpose? > Basic version: It's a peer-to-peer encrypted swarmed file sharing system that presents like Dropbox on the front end (i.e. "make a change to the filesystem on peer A and peers B-Z will replicate that change") and works something like Bittorrent on the back end in that files are sent in chunks but it offers functionality that Bittorrent does not, such as encrypted transfer, WoT authentication, etc. What if messages are lost permanently, e.g., due to hardware crash? > > What it you receive a create but a corresponding delete or update is > lost - then your information / picture of the file system state is wrong. > > What if you receive a file delete without a corresponding create? In the > absence of other information, can you even assume there *was* a create? > If these messages are sent in response to user actions, can they ever be > sent mistakenly? > > The ultimate answer to these questions is "If things get out of sync in a way that the system cannot resolve, it will be flagged for a human to resolve." There are things we do that mitigate them -- for example, a write-ahead log for messages received from peers -- but we acknowledge that we cannot resolve 100% of situations automatically. Neither can any other file replication service. (Dropbox, Box.com, etc) Also relevantly, differences are reconciled across multiple peers. If there's 5 peers in your replication set and the other 4 agree that there should be a file at path P but you don't have one then it's safe to assume that you missed a File-Create message. And yes, that comes with issues of its own (Q: What if it was deleted on your machine and none of the others got your File-Delete because you crashed before sending it? A: Worst case, the file gets recreated and the user deletes it again. Also, move files to a Trash folder in response to a File-Delete, don't actually delete them for a certain period of time) but again we fall back to human resolution. > -- You received this message because you are subscribed to the Google Groups "Racket Users" group. To unsubscribe from this group and stop receiving emails from it, send an email to racket-users+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/racket-users/CAE8gKof5ivZSN_nbPFtv0YJKyH8V-SexL1j6hqTeq0DYrY_8Rw%40mail.gmail.com.
