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variable / @typed/fx/Fx

flatMapConcurrentlyEffect

Maps each element of an Fx to an Effect, running them concurrently with a limit.

Package version
2.0.0-beta.7
Category
Concurrent work
Since
1.0.0

Follow one execution

Two permits admit a and b; c waits until b releases a permit. Results follow completion order. This scenario uses concurrent source deliveries: a pending source callback can wait for admission while another callback is already active.

Fx timelineflatMapConcurrentlyEffect(load, 2)flatMapConcurrentlyEffect
OperatorflatMapConcurrentlyEffect(load, 2)
Read this diagram

Follow each lane from left to right. Events stacked vertically share a tick; the green cursor marks the current time across every lane.

  • A value
    The text inside the pill is the emitted value.
  • Work starts
    The raised chevron starts an inner run (^ in the source).
  • The run returns
    The vertical bar ends this lane’s run.
  • A cause is delivered
    The exclamation mark belongs to this lane.
  • Work is interrupted
    The cross marks cancellation of this run.
  • Current time
    The line and diamond move together across all lanes.
  • Happening now
    A highlighted event is at the current tick.
  • Still ahead
    Muted, dashed values have not happened yet.
  • Time continues
    The lane’s arrow is not a return marker. An empty stretch can be quiet work that is still running.

Illustrated ticks start at 0. At 1×, one illustrated tick takes one second; captions specify real durations when timing matters. A cause or interruption belongs to its lane, and other work may continue. Scroll horizontally to inspect the rest of a long timeline.

Invalid limits fail with Cause.IllegalArgumentError; source and callback failures remain typed and callback services are added to requirements. The required Scope owns waiting and active Effects. Completion drains them; interruption cancels them and runs their finalizers.

Source implementation · Learn the surrounding model

Compare all Fx timelines →

Import

import { flatMapConcurrentlyEffect } from "@typed/fx/Fx";

Signatures

export declare const flatMapConcurrentlyEffect: {
    <A, B, E2, R2>(f: (a: A) => Effect.Effect<B, E2, R2>, concurrency: number): <E, R>(self: Fx<A, E, R>) => Fx<B, E | E2 | Cause.IllegalArgumentError, R | R2 | Scope.Scope>;
    <A, E, R, B, E2, R2>(self: Fx<A, E, R>, f: (a: A) => Effect.Effect<B, E2, R2>, concurrency: number): Fx<B, E | E2 | Cause.IllegalArgumentError, R | R2 | Scope.Scope>;
};

Why

This Effect-producing bounded merge avoids manual Fx.fromEffect conversion while making the callback’s concurrency budget part of the operation.

Concurrency, ordering, and cardinality

Every source value eventually starts one callback Effect, with no more than concurrency active at once. Each success emits exactly one value. Waiting work is retained, and results arrive by completion rather than source order.

Ownership and lifetime

Invalid limits fail with Cause.IllegalArgumentError; source and callback failures remain typed and callback services are added to requirements. The required Scope owns waiting and active Effects. Completion drains them; interruption cancels them and runs their finalizers.

Examples

import { Fx } from "@typed/fx"
import { Effect } from "effect"

const loaded = Fx.flatMapConcurrentlyEffect(
  Fx.fromIterable([
    { id: "one", wait: "20 millis" as const },
    { id: "two", wait: "20 millis" as const },
    { id: "three", wait: "1 millis" as const }
  ]),
  ({ id, wait }) => Effect.as(Effect.sleep(wait), id),
  2
)

Effect.runPromise(Effect.scoped(Fx.collectAll(loaded))).then(console.log)
// "three" remains queued until a permit is released

Other public imports

These import paths expose the same declaration. Each page retains its own public name and signature.

Source