[Dev] Existing p2p systems for getting offline node back up to date?

[nitin at borwankar.com]

Ray Ryan wrote:

>
> This bit about "gathering changes it missed" and "announcing any 
> offline changes" sounds like exactly what I said I don't want: storing 
> up messages for nodes that go offline.
>
> What I meant to imply was that some kind of diff operation is 
> performed on each of the subscribed documents, and that change 
> messages necessary to bring everything back into sync are broadcast 
> around the pool as a side effect of the offline node coming back 
> online. I have thoughts on how that might work, but I'll spare the list.


Groove is based on such diffs called "deltas" and basically sends deltas 
a round as a way of  syncronizing content.
My understanding, may be wrong, that this creates performance problems 
due to the large number of deltas being constantly propagated.
This is my first impression based on a naive reading of the Groove 
platform design, and I am sure I will be corrected if this is way off 
the mark.

>
>> The point is that no one has been storing up any delayed messages for 
>> the returning node while it has been away, or even remembers that it 
>> once existed.
>

As someone else mentioned email, it may be useful to note that email 
servers (or links to email servers) go down occasionally and sometimes 
stay unexpected and bad outages can cause them to be down for hours or 
sometimes ( in the case of individuals running their own server ) a day 
or two.
Backup email servers will hold messages for other servers that have made 
prior arrangments
SMTP provides a protocol message (ETRN) that the server on a host can 
send to a backup server to send queued messages.

While this (SMTP and ETRN) requires prior arrangement, there's no reason 
why, in a p2p environment peers can't advertise backup services  and 
other peers lease queue space and backup service from them, on a short 
term basis - perhaps with multiple peers simultaneously and perhaps with 
some payment protocol involved.

Peers need not provide this service so if you don't want to do this for 
other peers, you don't have to.
Aren't Yahoo and Hotmail just queueing up messages for you till you get 
them ?  

The p2p version of this is not likely to be free, if it is to be 
sustainable and worthwhile.  So for any useful service that a peer 
provides to others,  think (micro) payments as well.

Nitin Borwankar,
nitin at borwankar.com

>>
>> Now I'm very naive in this space. I have no idea if tools like this 
>> exist already, especially in the Open Source arena. I'd never even 
>> heard of distributed hash tables before joining this list (worth the 
>> price of admission right there!). But this is the tool that I'd love 
>> to have.
>>
>> Ray
>
>
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-- 
------------------------------------------------------------
The more idiot-proof you make it, the smarter the idiots get.

Nitin Borwankar
nitin at borwankar.com