Add a config for enforcing a minimum job reserve interval (default: 0 for now)

[smudge]

This is related to #41 and #42 insofar as a kind of DB-bound "spinloop" is still possible if a worker picks up jobs that take so little time that the worker immediately turns around and asks for more. As of now, there has been no way to tune the amount of time a worker should wait in between successful iterations of its run loop.

This introduces a configuration (min_reserve_interval) specifying a minimum number of seconds (default: 0 as this is not a major release) that a worker should wait in between successful job reserve queries. An existing config (sleep_delay) is still used to define the number of seconds (default: 5) that a worker should wait in between unsuccessful job reserve attempts (i.e. the queue is empty).

The job execution time is subtracted from min_reserve_interval when the worker sleeps, and if jobs take more than min_reserve_interval to complete than the worker will not sleep before the next reserve query.

/no-platform

[effron]

domainLGTM!

[jmileham]

Should a default behavior change like this be reserved for a major version? Like introduce the param at 0 seconds in 0.6 and then pop it to 1s at 1.0?

[jmileham]

domain lgtm too! Will leave platform to somebody closer/more current, if we want that. But I also think Nathan's currency satisfies that requirement for me for no-platform.