[mythtv-users] Mooting architecture for a DataDirect replacement

[Christopher X. Candreva]

On Thu, 21 Jun 2007, Jay R. Ashworth wrote:

> I was merely trying to propose an architecture that would make
> practical the distribution of the load of 200,000 Mythboxen looking for
> guide data every day.  NNTP would.

I used to run an NNTP system. I'm going to assume INN or it's replacement 
has gotten better, but it wasn't easy, and there is going to be 
significantly less experience in it today, especially most ISPs are 
outsourcing it.

There is another distributed-database system in place, complete with local 
caching and variable cache time: DNS . 

The anti-spam community has used DNS for years for real-time blacklists of 
IP address. In it's simplest form: Lets say you want to know if IP address 
1.2.3.4 is something you should accept mail from. Do a dns lookup  on 
4.3.2.1.blacklistexample.com . If it returns a value, it's blacklisted. DNS 
not found, it's OK  . Usually the IP returns is in 127.0.0.x , and by the 
last digit information as to the type of listing is returned.

Another example: The Clam AntiVirus project distributed the virus databases 
via simple http. They were doing http HEAD requests to check if a database 
was available, but the bandwidth was killing them. I suggesting using DNS to 
publish the current serial number of the database. If that number indicates 
a new version is available, the updater downloads a new copy of the virus 
DB. In this way, you can check for new virus signatures every 5 minutes, and 
it only costs a 58 byte UDP packet.

I can see a similar method, using DNS to indicate an update is available, 
triggering the transfer of an updated data set/file.


==========================================================
Chris Candreva  -- chris at westnet.com -- (914) 948-3162
WestNet Internet Services of Westchester
http://www.westnet.com/