Falling back to a disabled pool member, if all others are down?

Hi Erlend,

how about creating a "shadow pool" with same members and same monitors. Members in shadow pool will always remain in "enabled" state but may be marked by monitor as "down". An iRule will forward traffic to the shadow pool if all members of the default pool are "offline" or "disabled".

when LB_FAILED {
    pool pool_shadow
}

Or alternatively:

when CLIENT_ACCEPTED {
    if { [active_members pool_default] < 1 } {
        pool pool_shadow
    }
}

Thanks, Stephan

Not sure. If you Force Offline, instead of Disable then this ignores persistent connections. If this is not a problem then the pool member should be free of active connections a lot sooner so the time that it is unavailable would be reduced.

Perhaps not explicitly answering your question but my 2cents.

N

I'd suggest that if an app is so critical that you need to maintain HA even during maintenance, it's time for a 3rd node. Would you really ever want to send live traffic to a node undergoing maintenance?

What about enabling priority groups instead of disabling a node when preparing for a maintenance window? Give the live node a higher priority than the node going into maintenance, and change "priority group activation" to less than one member (or however many members are not going into maintenance)

What about enabling priority groups instead of disabling a node when preparing for a maintenance window? Give the live node a higher priority than the node going into maintenance, and change "priority group activation" to less than one member (or however many members are not going into maintenance)

Hi,

here is an generic iRule approach. Source address persistence is used. Other persistence methods not tested yet:

when LB_FAILED {
    foreach pool_member [members -list [LB::server pool]] {
        if { [LB::status pool [LB::server pool] member [getfield $pool_member " " 1] [getfield $pool_member " " 2]] ne "down" } {
            LB::reselect pool [LB::server pool] member [getfield $pool_member " " 1] [getfield $pool_member " " 2]
        }
    }
}

when PERSIST_DOWN {
    foreach pool_member [members -list [LB::server pool]] {
        if { [LB::status pool [LB::server pool] member [getfield $pool_member " " 1] [getfield $pool_member " " 2]] ne "down" } {
            LB::reselect pool [LB::server pool] member [getfield $pool_member " " 1] [getfield $pool_member " " 2]
        }
    }
}

when LB_SELECTED {
    persist add source_addr [IP::client_addr]
}

Thanks, Stephan