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Shahram_83722's avatar
Shahram_83722
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Jun 16, 2012

iRule to redirect based on path plus fallback host

I'm not super on iRules but need to write one that will redirect path A and B to pool1 and path C and D to pool2. I also need to incorporate a fallback host in case each of these pools don't have a member. I've come up with the following iRule. Can anyone tell me whether or not this is a sound iRule or if there is anything better I should write?

 

 

 

 

when HTTP_REQUEST {

 

 

switch -glob -- [string tolower [HTTP::path]] {

 

 

 

"/a*" -

 

"/b*" {

 

if {[active_members pool_1] < 1} {

 

Log and direct the client to Maintenance pool

 

log local0. "!!Maintenance page called for Pool1!!"

 

pool Fallback_Pool }

 

else {

 

pool pool_1

 

}

 

 

 

"/c*" -

 

"/d*" {

 

if {[active_members pool_2] < 1} {

 

Log and direct the client to Maintenance pool

 

log local0. "!!Maintenance page called for Pool2!!"

 

pool Fallback_Pool }

 

else {

 

pool pool_2

 

}

 

 

default { discard }

 

 

 

}

 

}

 

 

 

 

7 Replies

  • rather than an if statement inside the cases, just use the LB_FAILED event to catch when no pool members are available and assign to the fallback pool. I think this would be a more efficient way to handle this since both cases use the same fallback pool.
  • The rule you have looks okay. The curly braces weren't exactly correct, but I assume that's just an issue with the editing you did for the post.

    Here's your original version with balanced braces:

    when HTTP_REQUEST {
    
    switch -glob -- [string tolower [HTTP::path]] {
    
    "/a*" -
    "/b*"  {
    if {[active_members pool_1] < 1} {
     Log and direct the client to Maintenance pool
    log local0. "!!Maintenance page called for Pool1!!"
    pool Fallback_Pool
    } else {
    pool pool_1
    }
    }
    "/c*" -
    "/d*"  {
    if {[active_members pool_2] < 1} {
     Log and direct the client to Maintenance pool
    log local0. "!!Maintenance page called for Pool2!!"
    pool Fallback_Pool }
    else {
    pool pool_2
    }
    }
    default {
    discard
    }
    }
    }
    

    You could move the active_members check of the pool outside the switch statement to simplify the rule a little:

    when HTTP_REQUEST {
    
    switch -glob -- [string tolower [HTTP::path]] {
    
    "/a*" -
    "/b*"  {
    pool pool_1
    }
    "/c*" -
    "/d*"  {
    pool pool_2
    }
    default {
    discard
    return
    }
    }
    if {[active_members [LB::server pool]] < 1} {
     Log and direct the client to Maintenance pool
    log local0. "!!Maintenance page called for [LB::server pool]!!"
    pool Fallback_Pool
    }
    }
    

    Aaron
  • Posted By Brian on 06/18/2012 01:01 PM

     

    ...use the LB_FAILED event to catch when no pool members are available and assign to the fallback pool.

     

    That would work too :)

     

     

    Aaron

     

  • Thank you guys for the input. I greatly appreciate it.

     

     

    I've tried using the LB_FAILED before and it did not work for me, but the check for active members did so I'm not quite sure I want to use that. It could have been an error on my part...

     

     

    Aaron, the reason I kept the members check within the switch statement is because I don't want the absence of a member on one of the pools to trigger a fallback for the whole VS, although my fallback server can serve all paths.

     

     

    I saw you use the 'return' command. I've read the online documentation on it but haven't quite gotten an understanding of it. Could you tell me what it exactly does?
  • return exits out of the current event of the current iRule. So basically, the active_members check on the currently selected pool won't be run if the request is to a URI that's set for being dropped.

     

     

    The [LB::server pool] command will return the name of the currently selected pool. So it should work fine to move that check out of the switch statement.

     

     

    Aaron