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Andy_Clark_1335's avatar
Andy_Clark_1335
Icon for Nimbostratus rankNimbostratus
Jul 19, 2016

Switch between default pool and another virtual server, per request

My CDN sends requests to public_vs, an external facing virtual server. public_vs sends the request to proxy_pool, a pool of proxy servers. The proxy servers make changes to the request and proxy it application_vs, a different virtual server on the same LTM. application_vs sends the requests to application_pool, a pool of application servers.

CDN -> public_vs -> proxy_pool -> proxy_app_node -> application_vs -> application_pool

Depending upon request headers (ex. "True-Client-IP: 1.2.3.4"), I want to bypass the pool of proxy servers, sending the request to application_vs.

CDN -> public_vs -> application_vs -> application_pool

Test public_vs

Default pool: simple application that does not forward the request to application_vs (for testing) Assigned iRule public_irule:

        when CLIENT_ACCEPTED {
          set i 0
          log local0. "Client accepted"
        }

        when HTTP_REQUEST {
          incr i 1
          set true_ip [HTTP::header value "True-Client-IP"]
          log local0. "public_vs request $i: $true_ip"
          if {"$true_ip" eq "1.2.3.4"} {
            log local0. "switching to application_vs"
            virtual "application_vs"
          }
        }

        when CLIENT_CLOSED {
          log local0. "Client session closed after $i requests"
        }
application_vs

Assigned the iRule application_irule:

        when HTTP_REQUEST {
          set barip [HTTP::header value "True-Client-IP"]
          log local0. "application_vs: $barip"
          HTTP::respond 200 content "application_vs" Content-Type "text/html"
        }
JMeter test plan

The CDN sends many requests over a single HTTP connection. This is replicated in JMeter using a single thread group with two HTTP requests pointing to public_vs. The first has the header "True-Client-IP: 192.168.76.1", the second has "True-Client-IP: 1.2.3.4".

Test Results

Ran the JMeter test for 5 iterations, watching the F5 LTM log:

        16:32:10 public_irule : Client accepted
        16:32:10 public_irule : public_vs request 1: 192.168.76.1
        16:32:10 public_irule : public_vs request 2: 1.2.3.4
        16:32:10 public_irule : switching to application_vs
        16:32:10 application_irule : application_vs: 1.2.3.4
        16:32:10 public_irule : public_vs request 3: 192.168.76.1
        16:32:10 application_irule : application_vs: 192.168.76.1
        16:32:11 public_irule : public_vs request 4: 1.2.3.4
        16:32:11 public_irule : switching to application_vs
        16:32:11 application_irule : application_vs: 1.2.3.4
        16:32:11 public_irule : public_vs request 5: 192.168.76.1
        16:32:11 application_irule : application_vs: 192.168.76.1
        16:32:11 public_irule : public_vs request 6: 1.2.3.4
        16:32:11 public_irule : switching to application_vs
        16:32:11 application_irule : application_vs: 1.2.3.4
        16:32:11 public_irule : public_vs request 7: 192.168.76.1
        16:32:11 application_irule : application_vs: 192.168.76.1
        16:32:11 public_irule : public_vs request 8: 1.2.3.4
        16:32:11 public_irule : switching to application_vs
        16:32:11 application_irule : application_vs: 1.2.3.4
        16:32:11 public_irule : public_vs request 9: 192.168.76.1
        16:32:11 application_irule : application_vs: 192.168.76.1
        16:32:11 public_irule : public_vs request 10: 1.2.3.4
        16:32:11 public_irule : switching to application_vs
        16:32:11 application_irule : application_vs: 1.2.3.4
        16:32:11 public_irule : Client session closed after 10 requests
application delivery
BIG-IP
devops
iRules

2 Replies

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  • Andy_Clark_1335's avatar
    Andy_Clark_1335
    Icon for Nimbostratus rankNimbostratus
    Jul 19, 2016

    virtual causes all subsequent requests for the current connection to go through the second virtual server.

     

    I've tried using OneConnect profiles as described in SOL9800. However, I believe that only works for balancing pools. I have also tried adding LB::detach.

     

    Any suggestions or insight?

     

  • Vijay_E's avatar
    Vijay_E
    Icon for Cirrus rankCirrus
    Jul 19, 2016

    You can do this for packets without "True-Client-IP": CDN -> public_vs -> application_pool

    instead of doing this: CDN -> public_vs -> application_vs -> application_pool

    You can use an iRule attached to public_vs that will send traffic without "True-Client-IP" to the application_pool. Use OneConnect with 255.255.255.255 netmask in order to preserve the client IP at the server level. 

    when HTTP_REQUEST {
if { [HTTP::header exists "True-Client-IP"] } {
pool proxy_pool
} else {
pool application_pool
}
}