Re: [blogite] A decentralised "my blog has been updated" service

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From: Paul S. Brown (
Date: Sat Sep 07 2002 - 12:22:52 BST

On Saturday 07 September 2002 12:06 pm, Simon Willison wrote:
> We've been talking about this at work and as it poses an interesting
> challenge I thought I'd share it with the list. This is all completely
> hypothetical stuff, but it's a fun problem nontheless.
> Most (probably all) of us send a ping to when our blog is
> updated. These pings are then propagated once an hour to sites like,
> with the end result being that some of our sites can display lists of blogs
> on our blogrolls in order of their last update. There are other services
> linked in to that can alert people when their favourite blogs
> are updated, and all in all it's a pretty important service.
> The current system has two disadvantages:
> 1. It has a central point of failure (
> 2. It can have up to a one hour delay.
> The challenge then is to come up with a decentralised system to allow blogs
> to alert people (and bots and other sites / blogs) when the blog is
> updated.
> I've been thinking about a system where blogs can "subscribe" to other
> blogs. Subscribing involves sending a request to the blog in question
> (almost certainly using XML-RPC) saying "please message my XML-RPC server
> at URL when you update". Blogs have to keep track of who has subscribed
> and, when they are updated, send out a bunch of update messages.

Just thinking, but have the subscribe message contain a list of other blogs
that are subscribed to, and have this message re-propogate on every change,
you can now start to build up a routing table for blogs.

Once you have this table in place it should be theoretically possible to
design an algorithm which comes up with 2 routes for each blog, while
contacting no more than a certain number of other hosts.

You then send out the update for your blog to maybe 20 hosts, each of them
with explicit routing saying "propogate this to this list of hosts"

Another alternative would be to have the same route-finding process designate
hub hosts to whom updates could be sent and propogated from. Ultimately I am
going to sit down and think this one through and probably come up with hybrid
(hop count, loading) metric routing protocol for blog updates.

I'll think about this - it looks like more of a network design issue than
anything else.


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