What this plugin offers is a different scheduling algorithm, which we refer to as "even loading strategy".

Under this strategy, the scheduler prefers idle nodes absolutely over nodes that are doing something. Thus in the above example, BAR #1 will always run on Y, because X is currently building FOO #1. Even though it still has 3 idle executors, it will not be considered so long as there are other qualifying slaves that are completely idle.

However, idle executors are still idle, so if more builds are queued up, they will eventually occupy the other 3 executors of X, thereby using this slave to its fullest capacity. In other words, with this algorithm, the total capacity of the system does not change—only the order in which the available capacity is filled.

The strength of this algorithm is that you are more likely to get a fully idle node. Quite simply, executing a build on a fully idle system is faster than executing the same thing on a partially loaded system, all else being equal.

However, the catch is that all else may not be equal. If the node does not have a workspace already initialized for this job, you’ll pay the price of fully checking out a new copy, which can cancel other performance gains. In a nutshell, even loading is most useful for jobs which are slow to build, but for which the very first build on a node is not notably slower than any other.

The Even Scheduler plugin was introduced in Nectar 11.10.