effect-io-ai

Package: effect
Module: Effect

Effect.raceAll

Races multiple effects and returns the first successful result.

Details

This function runs multiple effects concurrently and returns the result of the first one to succeed. If one effect succeeds, the others will be interrupted.

If none of the effects succeed, the function will fail with the last error encountered.

When to Use

This is useful when you want to race multiple effects, but only care about the first one to succeed. It is commonly used in cases like timeouts, retries, or when you want to optimize for the faster response without worrying about the other effects.

Example (All Tasks Succeed)

import { Effect, Console } from "effect"

const task1 = Effect.succeed("task1").pipe(
  Effect.delay("100 millis"),
  Effect.tap(Console.log("task1 done")),
  Effect.onInterrupt(() => Console.log("task1 interrupted"))
)
const task2 = Effect.succeed("task2").pipe(
  Effect.delay("200 millis"),
  Effect.tap(Console.log("task2 done")),
  Effect.onInterrupt(() => Console.log("task2 interrupted"))
)

const task3 = Effect.succeed("task3").pipe(
  Effect.delay("150 millis"),
  Effect.tap(Console.log("task3 done")),
  Effect.onInterrupt(() => Console.log("task3 interrupted"))
)

const program = Effect.raceAll([task1, task2, task3])

Effect.runFork(program)
// Output:
// task1 done
// task2 interrupted
// task3 interrupted

Example (One Task Fails, Two Tasks Succeed)

import { Effect, Console } from "effect"

const task1 = Effect.fail("task1").pipe(
  Effect.delay("100 millis"),
  Effect.tap(Console.log("task1 done")),
  Effect.onInterrupt(() => Console.log("task1 interrupted"))
)
const task2 = Effect.succeed("task2").pipe(
  Effect.delay("200 millis"),
  Effect.tap(Console.log("task2 done")),
  Effect.onInterrupt(() => Console.log("task2 interrupted"))
)

const task3 = Effect.succeed("task3").pipe(
  Effect.delay("150 millis"),
  Effect.tap(Console.log("task3 done")),
  Effect.onInterrupt(() => Console.log("task3 interrupted"))
)

const program = Effect.raceAll([task1, task2, task3])

Effect.runFork(program)
// Output:
// task3 done
// task2 interrupted

Example (All Tasks Fail)

import { Effect, Console } from "effect"

const task1 = Effect.fail("task1").pipe(
  Effect.delay("100 millis"),
  Effect.tap(Console.log("task1 done")),
  Effect.onInterrupt(() => Console.log("task1 interrupted"))
)
const task2 = Effect.fail("task2").pipe(
  Effect.delay("200 millis"),
  Effect.tap(Console.log("task2 done")),
  Effect.onInterrupt(() => Console.log("task2 interrupted"))
)

const task3 = Effect.fail("task3").pipe(
  Effect.delay("150 millis"),
  Effect.tap(Console.log("task3 done")),
  Effect.onInterrupt(() => Console.log("task3 interrupted"))
)

const program = Effect.raceAll([task1, task2, task3])

Effect.runPromiseExit(program).then(console.log)
// Output:
// {
//   _id: 'Exit',
//   _tag: 'Failure',
//   cause: { _id: 'Cause', _tag: 'Fail', failure: 'task2' }
// }

See

race for a version that handles only two effects.

Signature

declare const raceAll: <Eff extends Effect<any, any, any>>(all: Iterable<Eff>) => Effect<Effect.Success<Eff>, Effect.Error<Eff>, Effect.Context<Eff>>

Source

Since v2.0.0