Expand description
This module defines a load-balanced pool of services that adds new services when load is high.
The pool uses poll_ready
as a signal indicating whether additional services should be spawned
to handle the current level of load. Specifically, every time poll_ready
on the inner service
returns Ready
, Pool
consider that a 0, and every time it returns Pending
, Pool
considers it a 1. Pool
then maintains an exponential moving
average over those
samples, which gives an estimate of how often the underlying service has been ready when it was
needed “recently” (see Builder::urgency
). If the service is loaded (see
Builder::loaded_above
), a new service is created and added to the underlying Balance
.
If the service is underutilized (see Builder::underutilized_below
) and there are two or
more services, then the latest added service is removed. In either case, the load estimate is
reset to its initial value (see Builder::initial
to prevent services from being rapidly
added or removed.
Structs§
- A builder that lets you configure how a
Pool
determines whether the underlying service is loaded or not. See the module-level documentation and the builder’s methods for details. - A dynamically sized, load-balanced pool of
Service
instances. - A wrapper around
MakeService
that discovers a new service when load is high, and removes a service when load is low. SeePool
.