Nortel Networks WEB OS 212777 - Manual (Page 229)

Web OS 10.0 Application Guide
Chapter 10: Health Checking n 229
212777-A, February 2002
Script-based health checking is intelligent in that it will only send the appropriate requests to
the relevant servers. In the example above, the first GET statement will only be sent to Real
Server 1 and Real Server 2. Going through the health-check statements serially will ensure that
all content is available by at least one real server on the remote site.
Configure the remote real server IP address (the virtual server IP address of the remote site) to
accept “any” URL requests. The purpose of the first GET is to check if Real Server 1 or Real
Server 2 is up—that is, to check if the remote site has at least one server for “images” content.
Either Real Server 1 or Real Server 2 will respond to the first GET health check.
If all the real server IP addresses are down, Real Server 7 (the virtual server IP address of the
remote site) will respond with an HTTP Redirect (respond code 302) to the health check. Thus,
the health check will fail as the expected response code is 200, ensuring that the HTTP Redi-
rect messages will not cause a loop.
Verifying Script-Based Health Checks
If a script fails, the expect line in the script that is not succeeding is displayed under the /
info/slb/real command:
The server is not responding to the get with the expect string.
When the script succeeds in determining the health of a real server, the following information
is displayed
:
>> # /info/slb/real 1
1: 205.178.13.225, 00:00:00:00:00:00, vlan 1, port 0, health 4, FAILED
real ports:
script 2, DOWN, current
send GET / HTTP/1.0\r\n\r\n
expect HTTP/1.0 200
>> # /info/slb/real 1
1: 205.178.13.223, 00:00:5e:00:01:24, vlan 1, port 2, health 4, up
real ports:
script 2, up, current