Friday, September 26, 2014

Change HTTP reply content with AppShape++

Lab goal

When a clients asks for beta/a2.html, return "Hello" instead.

Use VIP 10.136.85.14

Setup

I'll use my Loadbalancer Lab Setup.


The loadbalancer is Radware's Alteon VA version 29.5.1.0

The initial Alteon VA configuration can be found here.

Notice the group and hosts are preconfigured:

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/c/slb/real 1
        ena
        ipver v4
        rip 10.136.85.1
/c/slb/real 2
        ena
        ipver v4
        rip 10.136.85.2
/c/slb/real 3
        ena
        ipver v4
        rip 10.136.85.3
/c/slb/group 10
        ipver v4
        add 1
        add 2
        add 3

Alteon configuration

First, lets configure the VIP/virt.

Remember routing! The returning traffic needs to go through the Alteon, otherwise TCP will break. So we also need to configure Proxy IP/SNAT so return traffic will go through the Alteon.


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 /c/slb/virt 85_14
        ena
        vip 10.136.85.14
 /c/slb/virt 85_14/service 80 http
        group 10
 /c/slb/virt 85_14/service 80 http/pip
        mode address
        addr v4 10.136.85.200

Next we need to write the Appshape++ script:

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when HTTP_REQUEST {
    # retrieve URL from the request
    set url [HTTP::uri]
    set reply {
        <html>
        <body>
        <h1>Hello!</h1>
        <body>
        </html>
    }

    # check if URL is with /beta/a2.html
    if {[string match "/beta/a2.html" $url] == 1} {
        # change the URL and select SRV1
        HTTP::respond 200 content $reply
    }
}

-----END


  • Line 1-17 - When a request comes in do:
    • Line 3 - Extract the URL
    • Line 4-10 - Set a response content.
    • Lines 13-16 - If the URL is "beta/a2.html" then:
      • Line 15 - Respond with code 200 and the content we set earlier.
  • Line 19 - The end of the script.
Now lets import the script and apply it to the VIP/virt:


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 /c/slb/appshape/script respond
        ena
        import text 
 when HTTP_REQUEST {
     # retrieve URL from the request
     set url [HTTP::uri]
     set reply {
         <html>
         <body>
         <h1>Hello!</h1>
         <body>
         </html>
     }
     # check if URL is /beta/a2.html
     if {[string match "/beta/a2.html" $url] == 1} {
         # change the URL and select SRV1
         HTTP::respond 200 content $reply
     }
 }
 -----END
 
 /c/slb/virt 85_14/service 80 http/appshape
        add 10 respond

Test


Notice the "Hello!". Success!

Summary

After writing few AppShape++ , a pattern emerges: It really easy :)
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