Forum Discussion

Nimbostratus

Apr 10, 2007

LB::reselect not working as expected

I'm got an LB_SELECTED that is checking if the choice made by the LB is acceptable, and doing an LB::reselect if not. I setup an artificial condition in my lab in which no choice is acceptable. Based on the code below, what i'd expect to see is the connection be ultimately rejected after having looped through all the servers in the pool and determined that none of them were acceptable candidates. What i'm actually seeing is the LB::reselect happening twice, and on the second time, it's putting the connection on the server chosen by the LB, not looping to the next one according to the LB algo. (which is round-robin btw). There are 3 servers in the pool. Here is my LB_SELECTED rule:

when LB_SELECTED {

If we don't have the capacity to host this client on

the selected server, then reselect. If we've gone

through all the servers in the list, then reject.

if { [LB::server ratio] < $client_weight } {

if { $retry_count >= [active_members [LB::server pool]] } {

log local0. "Found no server of [active_members [LB::server pool]] in pool [LB::server pool] with enough capacity to handle $sender of weight $client_weight. Rejecting connection."

reject

return

} incr retry_count

log local0. "LB chose member ([LB::server addr]) with too little capacity ([LB::server ratio]) for sender $sender. Need at least $client_weight. Reselect try number $retry_count."

LB::reselect

}

Thanks in advance.

Dave

13 Replies

David_Bradley_2
Nimbostratus
Apr 12, 2007
Citizen,

Thanks for your help. I thought of doing that. I'd have to:

1) maintain a class with the same information that's already in the pool definition. If there were some way to find out the pool members from within the irule, then I would be nicer. But I could do this.

2) In order to "load" the class data with the current ratios, i'd have to make a pass through LB_SELECTED for each server in the pool. I guess the only way to reliably do this is via a "pool member " from the CLIENT_DATA event. i.e. pseudocode

CLIENT_DATA

foreach member in class

if member(capacity) uninitialized

pool

elsif member(capacity) > incoming client's weight

pool

endif

endfor

LB_SELECTED

if uninitialized capacity value for this member

member(capacity) = [LB::server ratio]

if member(capacity) < incoming client's weight

LB::reselect

endif

endif

Is this the best (or only) way you can think of to pull this off?

Dave

JRahm

Admin

Apr 12, 2007

I was thinking this could be done within the LB_SELECTED event:


when LB_SELECTED {
  set current_pool [LB::server pool]
  LB::detach
  foreach i in $::pool_members {
    pool $current_pool member $i
    set current_ratio [LB::server ratio]
     BUILD ARRAY LOGIC HERE 
    LB::detach
  }
   EXTRACT APPROPRIATE SELECTION FROM ARRAY HERE 
  pool $current_pool member $best_selection
}

Sorry, my TCL is fairly limited. Also, this is just a guess as to what's possible. I'm not sure the pool setting matters much until the event is finished, so it could all be for not.