TCP Payload String Swap for Oracle HA

Hi Matt --

Here's the basic iRule version of your pseudocode above:

rule RAC-SID-replacement_switch {
when CLIENT_ACCEPTED {
  TCP::collect
}
when CLIENT_DATA {
  set payload [TCP::payload]
}
when LB_SELECTED {
  switch [LB::server addr] {
    10.10.10.1 { ;  IP addr of vfcudb01b
      regsub -all "acmesid_vip" $payload "acmesid1" payload
      TCP::payload replace 0 [TCP::payload length] $payload
    }
    10.10.10.2 { ;  IP addr of vfcudb02b
      regsub -all "acmesid_vip" $payload "acmesid2" payload
      TCP::payload replace 0 [TCP::payload length] $payload
    }
    10.10.10.3 { ;  IP addr of vfcudb03b
      regsub -all "acmesid_vip" $payload "acmesid3" payload
      TCP::payload replace 0 [TCP::payload length] $payload
    }
    10.10.10.4 { ;  IP addr of vfcudb04b
      regsub -all "acmesid_vip" $payload "acmesid4" payload
      TCP::payload replace 0 [TCP::payload length] $payload
    }
  }
  TCP::release
  TCP::collect
}
}

For a more concise and scalable solution, you could instead use a class to maintain the relationship between IP, hostname, and sid value, and extract with "findclass" (Although in this example the hostname field is not necessary, it might be useful as a label/comment for admin purposes):

class mySIDs {
   type string
  10.10.10.1 acmesid1 vfcudb01b 
  10.10.10.2 acmesid2 vfcudb02b
  10.10.10.3 acmesid3 vfcudb03b
  10.10.10.4 acmesid4 vfcudb04b
}
rule RAC-SID-replacement_findclass {
when CLIENT_ACCEPTED {
  TCP::collect
}
when CLIENT_DATA {
  set payload [TCP::payload]
}
when LB_SELECTED {
  set mySID [getfield [findclass [LB::server addr] $::mySIDs] " " 2]
  if {$mySID != ""}{
    regsub -all "acmesid_vip" $payload "$mySID" payload
    TCP::payload replace 0 [TCP::payload length] $payload
  }
  TCP::release
  TCP::collect
}
}

Requests traversing either iRule will be forwarded to the VS's configured default pool regardless of whether any payload manipulation took place. The release/collect at the end ensures that subsequent requests on the same connection will be processed in the same manner.

HTH

(I'd be interested to hear back if this solved your problem so I can add it to the CodeShare.)

/deb