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Brad_Baker's avatar
Brad_Baker
Icon for Cirrus rankCirrus
Oct 01, 2013

Directing traffic based on query parameter

We need the ability to direct traffic to a specific node on our LTM load balancers based on query parameter.

 

So for instance if I enter www.foo.com/some-article?s=web-server1 the request would get sent to web-server1, likewise if I were to access www.foo.com/myarticle.php?s=web-server2 the request would get sent to web-server2.

 

I found something very close here: https://devcentral.f5.com/wiki/iRules.Select_pool_member_based_on_HTTP_query_string_parameter.ashx

 

The issue is that this selects the 0th, 1st, 2nd, Nth pool member from the active members of a pool but we want to use the server name not member number. So for instance my member servers may be called web-server5, web-server6, web-server7, web-server8

 

Its un-intuitive to call member=1 and expect to get web server five. You'd expect if ?member=1 then you'd get web-server1 (even though web-server5 is the first in this pool.) Is there some way to call the node name specifically instead of the member number?

 

Thanks Brad

 

application delivery
devops
iRules

5 Replies

  • What_Lies_Bene1's avatar
    What_Lies_Bene1
    Icon for Cirrostratus rankCirrostratus
    Oct 01, 2013

    If you map the query string name to the pool member IP address this should be very easy using the 'pool member x.x.x.x' command syntax.

     

  • Brad_Baker's avatar
    Brad_Baker
    Icon for Cirrus rankCirrus
    Oct 01, 2013

    I'm not sure I am following. Are you suggesting we do http://somedomain/somepage?s=192.168.0.15?

     

    If so I'm afraid that's even less intuitive. I would really like this to be as simple as possible. What I'm really concerned with is asking colleagues to remember s=1 is really web-server5. Asking them to remember web-server5 is really 192.168.0.156 is even more cumbersome.

     

    If I'm misunderstanding though please let me know.

     

  • Kevin_Stewart's avatar
    Kevin_Stewart
    Icon for Employee rankEmployee
    Oct 01, 2013

    As Steve relates, you need some (unfortunately manual) approach to mapping the web server's name to a node address. This can usually be done with a string-based data group. Example:

    Data group (ex. my_webserver_dg):

    "web-server1" := "10.10.10.10 80"
"web-server2" := "10.10.10.11 80"
"web-server3" := "10.10.10.12 80"
"web-server4" := "10.10.10.13 80"
"web-server5" := "10.10.10.14 80"

    And then an iRule that looks for the query string and routes accordingly, otherwise uses standard persistence:

    when HTTP_REQUEST {
    if { [string tolower [HTTP::uri]] starts_with "/myarticle.php?s=" } {
        set webserver [URI::query [string tolower [HTTP::uri]] s]
        if { [class match $webserver equals my_webserver_dg] } {
            set nodelist [split [class -value match $webserver equals my_webserver_dg] " "]
            node [lindex $nodelist 0] [lindex $nodelist 1]
        }
    }
}
  • StephanManthey's avatar
    StephanManthey
    Icon for Nacreous rankNacreous
    Oct 01, 2013

    Same datagroup. Slightly different iRule ([URI::query] does not work as expected in v10): 

    when CLIENT_ACCEPTED {
    set default_pool [LB::server pool]
}
when HTTP_REQUEST {
    if {[class match -value [string tolower [URI::query [HTTP::uri] s]] eq dg_name_node] ne ""} {
        node [class match -value [string tolower [URI::query [HTTP::uri] s]] eq dg_name_node] 80
    }
}
when LB_FAILED {
    log local0. "Selected server [LB::server] did not respond. Re-selecting node from $default_pool"
    pool $default_pool
    LB::reselect
}