Can I read the status of a pool in an iRule?

First of all, this should be something you can achieve without the use of an iRule. If you specify a default pool for the Virtual Server in question, and then select a fallback option that's appropriate, sending traffic to the secondary pool, you should be able to achieve this via normal configuration options which we always encourage.

 

 

If, for some reason, you do need to use an iRule, though, there are a couple of options for checking the status of the pool you're selecting in an iRule. The simplest would probably be to use the active_members command.

 

 

This command returns the number of active members in the specified pool. This would allow you to ensure that there was at least one member in the pool marked as "up" before sending traffic there.

 

 

You can read about the command in the iRules Wiki here: Click here

 

 

Included in the above link is this code snippet of a simple example rule using the command:

 

 

when HTTP_REQUEST {
  if { [active_members http_pool] >= 2 } {
    pool http_pool
  }
}

 

 

This could be modified very slightly to meet your above requirements. Assuming pool1 is http_pool, and pool2 is http_pool2:

 

 

when HTTP_REQUEST {
  if { [active_members http_pool] >= 1 } {
    pool http_pool
  } else {
    pool http_pool2
  }
}

 

 

HTH,

 

Colin

hi,

 

Cheers for the reply. Just what I needed. Just one other question... you said to do this in the normal config... how? I can see default and fallback persistance methods but only one (default) pool?

 

Cheers

 

Kev/.

Hi Kev -

 

 

You can set a fallback URL for the virtual server, but it would be to a specific host and URI, rather than a reference to another pool.

 

 

Instead of a rule or fallback host, you could use priority grouping in your pool to use the preferred servers if available, otherwise use the fallback servers. To do that, define all of the servers in the default pool, assigning a higher priority to the preferred servers, and a lower priority to the fallback servers, setting "Priority Group Activation" to "Less than 1 available members"

 

 

HTH

 

/deb