I recently read an article in Java Developer's Journal about Clustering BEA
WebLogic server. The author states:
The first line of clustering uses "DNS Round Robin" between the Web Clients
and the Web servers. ........... A Web client generally contacts the first
server on the list provided by DNS. After some timeout period, or if this
server fails, the client makes another DNS request and continues with a new
server.
I am wondering whether this is true for web broswers. If there are two
servers with same name but different IP address. After the web browser
browses serveral pages on one server and before it sends a subsequent
request, the server crashes. Now the connection will fail. Will the browser
transparently (without user notice) try a subsequent IP adress? If it does,
how does the browser get the next IP, from the list of the initial DNS
lookup or it has to do another lookup (If it does another lookup, the first
IP in the returned list could be the same as the first one)? Do IE and
Netscape browser support this kind of smartness?
Some server use Virtual IP adressing to achieve fault-tolerance. In one of
articles in Windows NT magazine,
Virtual IP addressing lets multiple servers respond to requests for one IP
address. For example, suppose you have three NT servers with the IP
addresses 222.222.231.1, 222.222.231.2, and 222.222.231.3. You can use
virtual IP addressing software to configure all three servers to use IP
address 222.222.231.10. You designate one server as the routing, or
scheduling, server. The scheduling server receives all inbound traffic and
routes requests for Web content to other servers based on load-balancing
parameters you set. If the scheduling server fails, virtual IP addressing
software assigns routing responsibilities to another server.
Because the Web interface uses one IP address, virtual IP addressing
achieves uninterrupted service unless all your Web servers fail.
Does apache server supports Virtual IP addressing? or is it done by thrid
party tools?
Thanks
Bing
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