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Zookeeper >> mail # user >> Use DNS to distribute list of servers, not client config


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Re: Use DNS to distribute list of servers, not client config
This is already supported in the zk client.

Cheers,

C
----- Original Message -----
From: Paul Sutter <[EMAIL PROTECTED]>
To: [EMAIL PROTECTED] <[EMAIL PROTECTED]>
Sent: Mon May 23 01:38:20 2011
Subject: Use DNS to distribute list of servers, not client config

A single DNS name can map to several IP addresses, and this complete list of
addresses is available to any DNS client.

If the Zookeeper client were to interpret DNS names so as to allow multiple
IP addresses from one DNS name, a single DNS name in the Zookeeper client
config to represent an arbitrary list of servers, so that the list of
servers could be changed centrally with no client config changes.

This is a widely supported standard feature of DNS. For example, we use this
at Quantcast to power the second most requested URL on the Internet, and we
get nice clean random distribution of client requests to IP addresses
despite all the weird DNS servers, proxies, and browsers out there.

Here's an example where edge.quantserve.com translates into 8 different
server IPs. Web browsers select one of these at random. Zookeeper should do
the same to simplify client configurations.

$ nslookup edge.quantserve.com
Server: 192.168.1.1
Address: 192.168.1.1#53

Non-authoritative answer:
edge.quantserve.com canonical name = map-js.quantserve.com.akadns.net.
map-js.quantserve.com.akadns.net canonical name anycast-americas.quantserve.com.akadns.net.
Name: anycast-americas.quantserve.com.akadns.net
Address: 64.94.107.58
Name: anycast-americas.quantserve.com.akadns.net
Address: 64.94.107.63
Name: anycast-americas.quantserve.com.akadns.net
Address: 64.94.107.37
Name: anycast-americas.quantserve.com.akadns.net
Address: 64.94.107.39
Name: anycast-americas.quantserve.com.akadns.net
Address: 64.94.107.23
Name: anycast-americas.quantserve.com.akadns.net
Address: 64.94.107.46
Name: anycast-americas.quantserve.com.akadns.net
Address: 64.94.107.24
Name: anycast-americas.quantserve.com.akadns.net
Address: 64.94.107.20