FixedWindow.pudu

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1/** @Limiter.FixedWindow.Module — at most N permits per fixed window */2module PuduLangResilience.Limiter.FixedWindow34import PuduLangResilience.Clock as Clock5import PuduLangResilience.Domain.Algorithms as Algorithms6import PuduLangResilience.Limiter.Engine as Engine7import PuduLangResilience.Limiter as Limiter89/** @Limiter.FixedWindow.Options — permits per window and the queue behind them */10export type Options = {11  permitLimit: Int,12  window: Int,13  autoReplenishment: Bool,14  queueLimit: Int,15  queueOrder: Limiter.QueueOrder,16  clock: Clock.Clock17}1819/// A hundred permits a second, moving by itself, with no queue.20export fn defaults() -> Options {21  Options{permitLimit: 100, window: 1000, autoReplenishment: true, queueLimit: 0, queueOrder: Limiter.OldestFirst, clock: Clock.system()}22}2324/// Every reason the options cannot be followed.25export fn validate(options: &Options) -> Array[Str] {26  var problems: Array[Str] = []27  if options.permitLimit < 1 { problems = problems.push("permitLimit must be at least 1") }28  if options.window < 1 { problems = problems.push("window must be at least 1 ms") }29  if options.queueLimit < 0 { problems = problems.push("queueLimit must not be negative") }30  problems31}3233/// A fixed window limiter whose first window starts now, or every reason it cannot be made.34export fn create(options: &Options) -> Result[Limiter.Limiter, Array[Str]] {35  let problems = validate(options)36  if !problems.isEmpty() { return Err(problems) }37  let queueing = Engine.Queueing{permitLimit: options.permitLimit, queueLimit: options.queueLimit, order: options.queueOrder}38  let start = Algorithms.Window{used: 0, start: Clock.now(&options.clock)}39  Ok(Engine.limiter(start, Algorithms.fixedWindow(options.permitLimit, options.window, options.autoReplenishment), &queueing, options.clock))40}41