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Create a stateful throttling object.

Source: R/crew_throttle.R
crew_throttle.Rd

Create an R6 object for throttling.

Usage

crew_throttle(
  seconds_max = 1,
  seconds_min = 0.001,
  seconds_start = seconds_min,
  base = 2
)

Arguments

seconds_max

Positive numeric scalar, maximum throttling interval

seconds_min

Positive numeric scalar, minimum throttling interval.

seconds_start

Positive numeric scalar, the initial wait time interval in seconds. The default is min because there is almost always auto-scaling to be done when the controller is created. reset() always sets the current wait interval back to seconds_start.

base

Numeric scalar greater than 1, base of the exponential backoff algorithm. increment() multiplies the waiting interval by base and decrement() divides the waiting interval by base. The default base is 2, which specifies a binary exponential backoff algorithm.

Value

An R6 object with throttle configuration settings and methods.

Details

Throttling is a technique that limits how often a function is called in a given period of time. crew_throttle() objects support the throttle argument of controller methods, which ensures auto-scaling does not induce superfluous overhead. The throttle uses deterministic exponential backoff algorithm (https://en.wikipedia.org/wiki/Exponential_backoff) which increases wait times when there is nothing to do and decreases wait times when there is something to do. The controller decreases or increases the wait time with methods accelerate() and decelerate() in the throttle object, respectively, by dividing or multiplying by base (but keeping the wait time between seconds_min and seconds_max). In practice, crew calls reset() instead of update() in order to respond quicker to surges of activity (see the update() method).

See also

Other throttle: crew_class_throttle

Examples

throttle <- crew_throttle(seconds_max = 1)
throttle$poll()
#> [1] TRUE
throttle$poll()
#> [1] FALSE