It is not uncommon for a machine that is running heterogeneous tasks
to have different tasks take vastly different amounts of resources.
Some may use a lot of ram but no cpu, etc.
Resource limit is a generic way to limit the amount of resources the
system can use assuming they can be statically defined for the task.

In our case resources are represented by an integer and as long as
subtracting that number from the system's resources returns a result
above or equal to zero we assume that those resources are available.

A resource map can contain many entries of keyword->integer.

At manager creation time a similar map is provided indicating the initial state.

Provider for amazon sqs

Generic things that can be executed on the queue.  Uses keyword dispatch