2017-11-03 10:08:58
good
Weight=1 for the load balancer
The load balancer in Blackhole uses a weight factor to select the best target. The default weight is 100.
The formula is simply
!number_of_connections/weight
. If you set the weight to 0, the target will be disabled. This is useful for maintenance. It is also useful
in case of failure. The monitoring system, while detecting a failure of one component, may simply reconfigure
the cluster away from it, but setting its weight to 0.

But there is another situation. You want to keep affinity. You want to keep local traffic local.
With Blackhole, having a load balancer between every service in the chain is easy. You do not
want to see your traffic jumping randomly between all servers of the cluster. For example, your
Apache SSL server should talk to the Apache application server on the same machine.

One trick to achieve this affinity is to set the weight of a distant server to 1 in Blackhole. The formula for weight=1 becomes simply
!number_of_connection/weight+1000
. The idea is that the distant server won't be used by the load balancer since its load factor is way higher than
the other servers on the local server. It will be used only when all local servers are down (weight = 0).