irule Performance question

I'll ditto Colin's comments. I've got a few more as well.

1. Try to avoid unnecessary processing

2. Try to avoid unnecessary use of session variables.

With that said, here's an equivalent iRule (you better double check though) that only uses one local variable. I figured since you were doing a "string tolower" on the [HTTP::host] value in each check, it would be a bit more efficient to do it once and store it. It's probably a wash but I think it reads better personally... I didn't do it for the first "string tolower" on the "HTTP::uri" as that was done only once.

when HTTP_REQUEST {
  set host [string tolower [HTTP::host]]
  if { 0 != [matchclass [string tolower [HTTP::uri]] contains $::G2TestStaticFileTypes] } {
    pool G2TestWebClusterIIS80    
  } elseif { 0 != [matchclass $host contains $::G2TestCluster1] } {
    if { [HTTP::host] contains "reports." } {
      pool G2TestWebCluster1Reports
    } else {
      pool G2TestWebCluster1Tomcat8080
    }
  } elseif { 0 != [matchclass $host contains $::G2TestCluster2] } {
    if { [HTTP::host] contains "reports." } {
      pool G2TestWebCluster2Reports
    } else {
      pool G2TestWebCluster2Tomcat8080
    }
  } elseif { 0 != [matchclass $host contains $::G2TestCluster3] } {
    if { [HTTP::host] contains "reports." } {
      pool G2TestWebCluster3Reports
    } else {
      pool G2TestWebCluster3Tomcat8080
    }
  } elseif { 0 != [matchclass $host contains $::G2TestCluster4] } {
    if { [HTTP::host] contains "reports." } {
      pool G2TestWebCluster4Reports
    } else {
      pool G2TestWebCluster4Tomcat8080
    }
  } elseif { 0 != [matchclass $host contains $::G2TestCluster5] } {
    if { [HTTP::host] contains "reports." } {
      pool G2TestWebCluster5Reports
    } else {
      pool G2TestWebCluster5Tomcat8080
    }
  }
}

Now, not that you want to go this route, but here's an alternate solution that makes use of a couple of variables and dynamic pool names that may or may not help you in the future.

when HTTP_REQUEST {
  set host [string tolower [HTTP::host]]
  set idx 0
  if { 0 != [matchclass [string tolower [HTTP::uri]] contains $::G2TestStaticFileTypes] } {
    pool G2TestWebClusterIIS80    
  } elseif { 0 != [matchclass $host contains $::G2TestCluster1] } {
    set idx 1
  } elseif { 0 != [matchclass $host contains $::G2TestCluster2] } {
    set idx 2
  } elseif { 0 != [matchclass $host contains $::G2TestCluster3] } {
    set idx 3
  } elseif { 0 != [matchclass $host contains $::G2TestCluster4] } {
    set idx 4
  } elseif { 0 != [matchclass $host contains $::G2TestCluster5] } {
    set idx 5
  }
  if { 0 != idx } {
    if { $host contains "reports." } {
      set pool_name "G2TestWebCluster${idx}Reports"
    } else {
      set pool_name "G2TextWebCluster${idx}Tomcat8080"
    }
    if { [catch { pool $pool_name } ] } { 
      log local0. "Error assinging pool to $pool_name"
    }
  }
}

There are ways to optimize this as well, but I thought I'd throw it out there for the fun of it. Notice the catch command surrounding the pool assignment. This is done because when using variable names, you do not have the benefit of config time parsing errors for pools that aren't defined. The catch will cause the iRule to not halt it's processing due to the error it would produce if the pool didn't exist.

Hope this helps...

-Joe