iRule behavior when pools are down

Hi Rick,

 

 

TMM would send a TCP reset as if the iRule wasn't there and the default pool was down. If you want to check the status of the pool before assigning it, you can use active_members. Or you could use the LB_FAILED event to handle this after a load balancing failure occurs.

 

 

http://devcentral.f5.com/wiki/iRules.active_members.ashx

 

http://devcentral.f5.com/wiki/iRules.lb_failed.ashx

 

 

You could also replace the if/elseif/else chain with a switch statement:

 

http://devcentral.f5.com/wiki/iRules.switch.ashx

 

 

Aaron

hello,

 

 

 

 

You can handle this situation intelligently when this occurs.

 

 

There could be 2 scenarios when pool is "down":

 

 

 

1. All pool members are down [ health check failed ] or disabled manually or connection limit reaches - high demand

 

2. Pool is emtpy [ yes you can have an empty pool in LTM :) ]

 

 

In my opinion, your iRule will look like this:

 

 

when HTTP_REQUEST {

 

if { [HTTP::host] starts_with "host1" } {

 

 

check if all members are down or disable then send to virtual waiting room that may send you back for retry

 

if { [active_members srvpool1] == 0 } {

 

HTTP::redirect "http://sorry.domain.com/pleasewait.html?[HTTP::host][HTTP::uri]"

 

}

 

 

check if pool is empty, means maintenance is in progress

 

if { ![members srvpool1] } {

 

 

log local0. "Pool is empty" ;

 

HTTP::redirect "http://sorry.domain.com/maint.html"

 

}

 

 

if all good then just proceed to the pool

 

pool srvpool1

 

 

} elseif { [HTTP::host] starts_with "host2" } {

 

pool srvpool2

 

} elseif { [HTTP::host] starts_with "host3" } {

 

pool srvpool3

 

} elseif { [HTTP::host] starts_with "host4" } {

 

pool srvpool4

 

} else {

 

pool default-pool

 

}

 

}

 

 

Hope it helps.

Thanks guys!