March 2007
Intermediate to advanced
304 pages
11h 12m
English
Content preview from Linux System Administration
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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 ...
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I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.