GeoIP and maintaining high availability

[Tomasz Chmielewski]

Am 09.07.2010 22:30, Dave Knight wrote:
> Hi Tomasz,
>
> On 2010-07-09, at 10:26 AM, Tomasz Chmielewski wrote:
>
>> Hi,
>>
>> I'm about to set up bind with GeoIP patches.
>>
>> What I'm not sure, is how do you guys handle high availability?
>>
>> Suppose I have zones for Americas and Europe, and a destination server in Europe dies - how do you handle it so that new (i.e. web) requests hit American servers only?
>>
>> Set TTL to low values (i.e. 10 minutes max) and reconfigure the zones if European servers are down? Something else?
>>
>> I assume typical hosting, without access to sophisticated network settings, like BGP.
>
>
> I think that you're confusing two issues. DNS has redundancy baked in.
>
> Let's say you have 2 nameservers
>
> 	ns-europe.example.com ( which is physically located in North America )
> 	ns-americas.example.com ( which is physically located in Europe )

No no.

I'm considering the situation where it is not the nameserver which 
failed, but say, a webserver in Europe.

Let's say we have a webserver (webserver.example.com):
- in Europe, with a 10.1.1.1 IP address
- in US, with IP 10.2.2.2 address.

When a user in Europe asks any of the name servers for A record for , 
he/she will receive 10.1.1.1. Now, let's suppose the webserver in Europe 
died - so 10.1.1.1 is unreachable. In the meantime, 10.2.2.2 is still 
reachable, but European users will be pointed to 10.1.1.1.

What is the best way to provide "high availability", assuming you don't 
have BGP, anycast and similar goodies available?

I though of setting TTL i.e. to 10 minutes and running some heartbeat 
process which would check if the webservers are available in both US and 
Europe.
Then, if any webserver fails, reconfigure zones accordingly.

Unless there are some better ways to do it?


-- 
Tomasz Chmielewski
http://wpkg.org