effect-io-ai

Package: effect
Module: Schedule

Schedule.fixed

Returns a Schedule that recurs on the specified fixed interval and outputs the number of repetitions of the schedule so far.

When to use

Use when recurrences should stay aligned to a regular cadence.

Gotchas

If the action run between recurrences takes longer than the interval, the next recurrence happens immediately, but missed intervals are not replayed.

|-----interval-----|-----interval-----|-----interval-----|
|---------action--------||action|-----|action|-----------|

Example (Repeating on fixed intervals)

import { Console, Effect, Schedule } from "effect"

// Fixed interval schedule - recurs on a one-second cadence
const everySecond = Schedule.fixed("1 second")

// Health check that runs at fixed intervals
const healthCheck = Effect.gen(function*() {
  yield* Console.log("Health check")
  yield* Effect.sleep("200 millis") // simulate health check work
  return "healthy"
}).pipe(
  Effect.repeat(Schedule.fixed("2 seconds").pipe(Schedule.upTo({ times: 5 })))
)

// Difference between fixed and spaced:
// - fixed: maintains constant rate regardless of action duration
// - spaced: waits for the duration AFTER each action completes

const longRunningTask = Effect.gen(function*() {
  yield* Console.log("Task started")
  yield* Effect.sleep("1.5 seconds") // Longer than interval
  yield* Console.log("Task completed")
  return "done"
})

// Fixed schedule: if task takes 1.5s but interval is 1s,
// next execution happens immediately (no pile-up)
const fixedSchedule = longRunningTask.pipe(
  Effect.repeat(Schedule.fixed("1 second").pipe(Schedule.upTo({ times: 3 })))
)

// Comparing with spaced (waits 1s AFTER each task)
const spacedSchedule = longRunningTask.pipe(
  Effect.repeat(Schedule.spaced("1 second").pipe(Schedule.upTo({ times: 3 })))
)

const program = Effect.gen(function*() {
  yield* Console.log("=== Fixed Schedule Demo ===")
  yield* fixedSchedule

  yield* Console.log("=== Spaced Schedule Demo ===")
  yield* spacedSchedule
})

See

• spaced for delaying after each action completes

Signature

declare const fixed: (interval: Duration.Input) => Schedule<number>

Source

Since v2.0.0