kumo.make_egress_pool
Defines an egress pool, which is a collection of weighted egress sources associated with the source of outbound traffic from the MTA.
A given scheduled queue can be associated with a pool and it will then use Weighted Round Robin (WRR) to distribute sends from that scheduled queue across the IPs contained within its associated pool. When a scheduled queue is idle for approximately 10 minutes, it will idle out and the round robin state will be reset for the next send.
Info
The Weighted Round Robin implementation in kumomta is considered to be probabilistic, achieving the configured distribution only when the rate of sending is sufficiently high (at least 1 message to a given site every few minutes), and is scoped per-scheduled-queue. There is no whole-machine nor whole-cluster coordination in the round robin implementation as those techniques introduce bottlenecks that limit scalability and are unnecessary at the kinds of volumes where it is important to implement distribution across sending IPs.
This function is intended to be used inside your get_egress_pool event handler.
PARAMS is a lua table which may have the following keys: