effect-io-ai

Package: effect
Module: Effect

Effect.repeatOrElse

Repeats an effect with a schedule, handling failures using a custom handler.

Details

This function allows you to execute an effect repeatedly based on a specified schedule. If the effect fails at any point, a custom failure handler is invoked. The handler is provided with both the failure value and the output of the schedule at the time of failure. This enables advanced error recovery or alternative fallback logic while maintaining flexibility in how repetitions are handled.

For example, using a schedule with recurs(2) will allow for two additional repetitions after the initial execution, provided the effect succeeds. If a failure occurs during any iteration, the failure handler is invoked to handle the situation.

Example

import { Effect, Schedule } from "effect"

let count = 0

// Define an async effect that simulates an action with possible failures
const action = Effect.async<string, string>((resume) => {
  if (count > 1) {
    console.log("failure")
    resume(Effect.fail("Uh oh!"))
  } else {
    count++
    console.log("success")
    resume(Effect.succeed("yay!"))
  }
})

const policy = Schedule.addDelay(
  Schedule.recurs(2), // Repeat for a maximum of 2 times
  () => "100 millis" // Add a delay of 100 milliseconds between repetitions
)

const program = Effect.repeatOrElse(action, policy, () =>
  Effect.sync(() => {
    console.log("orElse")
    return count - 1
  })
)

Effect.runPromise(program).then((n) => console.log(`repetitions: ${n}`))

Signature

declare const repeatOrElse: { <R2, A, B, E, E2, R3>(schedule: Schedule.Schedule<B, A, R2>, orElse: (error: E, option: Option.Option<B>) => Effect<B, E2, R3>): <R>(self: Effect<A, E, R>) => Effect<B, E2, R2 | R3 | R>; <A, E, R, R2, B, E2, R3>(self: Effect<A, E, R>, schedule: Schedule.Schedule<B, A, R2>, orElse: (error: E, option: Option.Option<B>) => Effect<B, E2, R3>): Effect<B, E2, R | R2 | R3>; }

Source

Since v2.0.0