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Hi Huatao,
Sorry for the late reply but I took off this weekend.
huatao wrote:
>
> Thank you, ratz,
> and thank you, steve
>
> But how could i know the load-balancer is doing it's work?
> Said i'm using LVS to balance HTTP traffic via NAT, RR scheduling,
> do i have to keep a same copy of those web stuff, such as html, cgi
> and database for better performance? It's hard for me to keep them
That's basically the approach. Since you're suggesting to load balance
http-traffic, this is extremely easy. (Hope I correctly understand your
problem) Take 2 or more realserver with the same DocumentRoot and the
same ../cgi-bin/. The synchronisation can be done via rsync and if you
want to have it secure rsync -e ssh ... . Since we can assume you don't
change your static webserver content too often and you also don't change
your cgi's you can do a cronjob rsyncing the webservers let's say every
three hours. This poor-man-but-extremely-well-working solution has proven
very reliable in productionary envirement for mid-range webserver-farms.
> synchro. The only way i could think of to check if the load-balancer
> is doing it's work is that: i put different homepage on each real
> server and "Refresh" http://VIP all the time, to see if the page
> fetched by browser changes by turn. I don't have any better ideas,:-)
> Help me?
> Thanks!
Ok, the second thing you'd like to know is how to check the service
running on a realserver (please correct me if I'm wrong): I call this
healthchecking (commercial loadbalancer vendors tend to call it alike)
What you do here is: The loadbalancer runs a daemon that checks periodi-
cally all realservers services like for example http, telnet. This check
can be from poor-man solution (icmp) to highend (connect to webserver,
start a request to the database and verify it's content). Your daemon
then performes those checks agains all realservers and if a check fails
the realserver will be taken out. The check goes on and if the server
or service comes back, it will be inserted again into the table with
ipvsadm. NOTE: This works EXTREMELY well!!! Only negative aspect: You
have to write your own daemon. LVS doesn't provide this for several
reasons.
Hope this answers your questions:
Best regards,
Roberto Nibali, ratz
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