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load balancing a web application

Posted on 2013-12-03
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Last Modified: 2013-12-09
I am developing an ASP.NET web application with will run with A10 Model AX3030 for load balancing.

The users will connect to a computer through VPN or Terminal Server and from there they will click on a IE shortcut with URL pointing to the load balancer.

Since all the request to load balancer will originate from the same machine,
do I need to do anything special in the web application that will help the load balancer ?
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Question by:vu3lmg
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by:giltjr
ID: 39693112
Not familiar with the AX3030.  How does it choose to load balance the traffic?

As to your web application, do you have to authenticate?  If so do all http requests from a single user have to go back to the same server?  That is do you require sticky/persistent  sessions?

If so they somehow between your app and the AX3030 you will need to differentiate between user#1 and user#2 when the have the same IP address.
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by:vu3lmg
ID: 39693216
Dear giltjr

Thanks for the quick response.

Yes my application does authenticate each user.  
Yes all http requests from a single user have to go to the same web-server.

Can A10 load balancer use the ASP.NET_SessionId cookie to distinguish requests from different users ?
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by:giltjr
giltjr earned 500 total points
ID: 39693319
Not sure, I've never used an A10.  I've only used BigIP F5's and they can.    

The F5 would do this via what they call iRules, which is a script that is run for each connection that it is load balancing.  It would setup an internal session persistence record that would map the ASP.NET_SessionId  to the back end server.  We do this today using the JSESSIONID for Java.

I found an pdf on how to setup the AX to load balance Exchange.  I know its not what you are doing, but I did find that the A10 AX stuff has what it calls "aFlex Script".  Looking at it it looks almost exactly like F5's iRules.  Even down to have a persist function uie.  

http://www.a10networks.com/resources/files/DG_Exchange.pdf

So based on that I am sure that somebody has an aFlex Script to use the ASP.NET_SessionId for uie persistance.
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by:vu3lmg
ID: 39693609
Dear giltjr

I am studying the document you've mentioned. In the mean time can you please reply my last question above (do I need to do anything special in the web application that will help the load balancer ?).
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by:giltjr
ID: 39693696
No.
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by:vu3lmg
ID: 39693744
Dear giltjr
Thanks for the above reply.

I am planning to write an aFlex script that will check for value of the cookie named ASP.NET_SessionId for persistence.  
Is that a correct approach ?
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Expert Comment

by:giltjr
ID: 39693764
Yes.  If A10 does not provide samples, I'll point you to a F5 sample that you you should be able to convert easily.
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by:vu3lmg
ID: 39694073
Please send me the links to F5 sample.
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giltjr earned 500 total points
ID: 39694215
You may need to create a id on the site.  Of couse you need to tweak this to meet coding requirements of your load balancer, but you should get the idea.

https://devcentral.f5.com/wiki/iRules.Universal-Persistence-iRule-based-upon-ASP-NET-SessionId.ashx
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Author Closing Comment

by:vu3lmg
ID: 39706461
Got the concept.  Will get back if I have more questions.
Thanks for the quick replies.
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