
Load Balancing and High Availability
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Sep 11 22:59:45 mail ldirectord[8543]: Deleted fallback server: 127.0.0.1:80
( x 70.253.158.44:80)
Sep 11 22:59:46 mail ldirectord[8543]: Added real server: 70.253.158.45:80
( x 70.253.158.44:80) (Weight set to 1)
Back on web1 and web2, check the Apache access logs. The director should demand
director.html every
checkinterval seconds:
70.253.158.44 - - [11/Sep/2006:22:49:37 -0500] "GET /director.html HTTP/1.1"
200 11 "-" "libwww-perl/5.803"
70.253.158.44 - - [11/Sep/2006:22:49:39 -0500] "GET /director.html HTTP/1.1"
200 11 "-" "libwww-perl/5.803"
In your browser, go to the virtual site URL http://70.253.158.42/which.html, and you
should see either:
I'm web1
or:
I'm web2
If the load balancer is broken or one of the web servers is down, you might always
get a response from the same web server.
Now, stop Apache on web1:
# /etc/init.d/apache stop
Reload/refresh your browser page to access http://70.253.158.42/which.html again.
You should always get the response:
I'm web2
Adding HA to LB
The load balancer is a single point of failure. If it starts pining for the fjords, the web
servers behind it will become inaccessible. To make the system more reliable, you
can install a second load balancer in an HA configuration with the first. Detailed
instructions, which use the Ultra Monkey package that you’ve already installed, can
be found in “How To Set Up A Loadbalanced High-Availability ...