<Key, A, E, R>(self: ScopedCache<Key, A, E, R>): Effect.Effect<Array<Key>>Retrieves all active keys from the cache, automatically filtering out expired entries.
When to use
Use to inspect currently cached unexpired keys without running cache lookups.
Gotchas
Expired entries are removed and their scopes are closed while filtering.
Source effect/ScopedCache.ts:73917 lines
export const const keys: <Key, A, E, R>(
self: ScopedCache<Key, A, E, R>
) => Effect.Effect<Array<Key>>
Retrieves all active keys from the cache, automatically filtering out expired entries.
When to use
Use to inspect currently cached unexpired keys without running cache lookups.
Gotchas
Expired entries are removed and their scopes are closed while filtering.
keys = <function (type parameter) Key in <Key, A, E, R>(self: ScopedCache<Key, A, E, R>): Effect.Effect<Array<Key>>Key, function (type parameter) A in <Key, A, E, R>(self: ScopedCache<Key, A, E, R>): Effect.Effect<Array<Key>>A, function (type parameter) E in <Key, A, E, R>(self: ScopedCache<Key, A, E, R>): Effect.Effect<Array<Key>>E, function (type parameter) R in <Key, A, E, R>(self: ScopedCache<Key, A, E, R>): Effect.Effect<Array<Key>>R>(self: ScopedCache<Key, A, E, R>(parameter) self: {
state: State<Key, A, E>;
capacity: number;
lookup: (key: Key) => Effect.Effect<A, E, R | Scope.Scope>;
timeToLive: (exit: Exit.Exit<A, E>, key: Key) => Duration.Duration;
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
}
interface ScopedCache<in out Key, in out A, in out E = never, out R = never>A scoped cache whose values are acquired by a lookup effect and stored in
per-entry scopes.
When to use
Use to cache values that acquire scoped resources and must release those
resources when entries expire, are evicted, or are invalidated.
Details
Concurrent requests for the same key share the same in-flight lookup.
Entries can expire based on the lookup exit, are evicted when capacity is
exceeded, and release their entry scopes when invalidated, evicted, expired,
or when the cache's owning scope closes.
ScopedCache<function (type parameter) Key in <Key, A, E, R>(self: ScopedCache<Key, A, E, R>): Effect.Effect<Array<Key>>Key, function (type parameter) A in <Key, A, E, R>(self: ScopedCache<Key, A, E, R>): Effect.Effect<Array<Key>>A, function (type parameter) E in <Key, A, E, R>(self: ScopedCache<Key, A, E, R>): Effect.Effect<Array<Key>>E, function (type parameter) R in <Key, A, E, R>(self: ScopedCache<Key, A, E, R>): Effect.Effect<Array<Key>>R>): import EffectEffect.interface Effect<out A, out E = never, out R = never>The Effect interface defines a value that lazily describes a workflow or
job. The workflow requires some context R, and may fail with an error of
type E, or succeed with a value of type A.
When to use
Use when you need to represent a lazy, composable workflow that can require
services, fail with a typed error, or succeed with a typed value.
Details
Effect values model resourceful interaction with the outside world,
including synchronous, asynchronous, concurrent, and parallel interaction.
They use a fiber-based concurrency model, with built-in support for
scheduling, fine-grained interruption, structured concurrency, and high
scalability.
To run an Effect value, you need a Runtime, which is a type that is
capable of executing Effect values.
Effect<interface Array<T>Array<function (type parameter) Key in <Key, A, E, R>(self: ScopedCache<Key, A, E, R>): Effect.Effect<Array<Key>>Key>> =>
import corecore.const withFiber: <
A,
E = never,
R = never
>(
evaluate: (
fiber: FiberImpl<unknown, unknown>
) => Effect.Effect<A, E, R>
) => Effect.Effect<A, E, R>
fiber: effect.FiberImpl<unknown, unknown>(parameter) fiber: {
id: number;
interruptible: boolean;
currentOpCount: number;
currentLoopCount: number;
_stack: Array<Primitive>;
_observers: Array<(exit: Exit.Exit<A, E>) => void>;
_exit: Exit.Exit<A, E> | undefined;
_currentExit: Exit.Exit<A, E> | undefined;
_children: Set<FiberImpl<any, any>> | undefined;
_interruptedCause: Cause.Cause<never> | undefined;
_yielded: Exit.Exit<any, any> | (() => void) | undefined;
context: Context.Context<never>;
currentScheduler: Scheduler.Scheduler;
currentTracerContext: Tracer.Tracer["context"];
currentSpan: Tracer.AnySpan | undefined;
currentLogLevel: LogLevel.LogLevel;
minimumLogLevel: LogLevel.LogLevel;
currentStackFrame: StackFrame | undefined;
runtimeMetrics: Metric.FiberRuntimeMetricsService | undefined;
maxOpsBeforeYield: number;
currentPreventYield: boolean;
_dispatcher: Scheduler.SchedulerDispatcher | undefined;
currentDispatcher: SchedulerDispatcher;
getRef: <X>(ref: Context.Reference<X>) => X;
addObserver: (cb: (exit: Exit.Exit<unknown, unknown>) => void) => () => void;
interruptUnsafe: (fiberId?: number | undefined, annotations?: Context.Context<never> | undefined) => void;
pollUnsafe: () => Exit.Exit<unknown, unknown> | undefined;
evaluate: (effect: core.Primitive) => void;
runLoop: (effect: core.Primitive) => typeof core.Yield | Exit.Exit<unknown, unknown>;
getCont: <S extends core.contA | core.contE>(symbol: S) => (core.Primitive & Record<S, (value: any, fiber: effect.FiberImpl) => core.Primitive>) | undefined;
yieldWith: (value: Exit.Exit<any, any> | (() => void)) => core.Yield;
children: () => Set<Fiber.Fiber<any, any>>;
pipe: () => unknown;
setContext: (context: Context.Context<never>) => void;
currentSpanLocal: Span | undefined;
}
self: ScopedCache<Key, A, E, R>(parameter) self: {
state: State<Key, A, E>;
capacity: number;
lookup: (key: Key) => Effect.Effect<A, E, R | Scope.Scope>;
timeToLive: (exit: Exit.Exit<A, E>, key: Key) => Duration.Duration;
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
}
ScopedCache<Key, A, E, R>.state: State<Key, A, E>state._tag: "Open" | "Closed"_tag === "Closed") return import effecteffect.const succeed: <A>(
value: A
) => Effect.Effect<A>
const state: {
readonly _tag: "Open"
readonly map: MutableHashMap.MutableHashMap<
Key,
Entry<A, E>
>
}
self: ScopedCache<Key, A, E, R>(parameter) self: {
state: State<Key, A, E>;
capacity: number;
lookup: (key: Key) => Effect.Effect<A, E, R | Scope.Scope>;
timeToLive: (exit: Exit.Exit<A, E>, key: Key) => Duration.Duration;
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
}
ScopedCache<Key, A, E, R>.state: State<Key, A, E>state
const const now: numbernow = fiber: effect.FiberImpl<unknown, unknown>(parameter) fiber: {
id: number;
interruptible: boolean;
currentOpCount: number;
currentLoopCount: number;
_stack: Array<Primitive>;
_observers: Array<(exit: Exit.Exit<A, E>) => void>;
_exit: Exit.Exit<A, E> | undefined;
_currentExit: Exit.Exit<A, E> | undefined;
_children: Set<FiberImpl<any, any>> | undefined;
_interruptedCause: Cause.Cause<never> | undefined;
_yielded: Exit.Exit<any, any> | (() => void) | undefined;
context: Context.Context<never>;
currentScheduler: Scheduler.Scheduler;
currentTracerContext: Tracer.Tracer["context"];
currentSpan: Tracer.AnySpan | undefined;
currentLogLevel: LogLevel.LogLevel;
minimumLogLevel: LogLevel.LogLevel;
currentStackFrame: StackFrame | undefined;
runtimeMetrics: Metric.FiberRuntimeMetricsService | undefined;
maxOpsBeforeYield: number;
currentPreventYield: boolean;
_dispatcher: Scheduler.SchedulerDispatcher | undefined;
currentDispatcher: SchedulerDispatcher;
getRef: <X>(ref: Context.Reference<X>) => X;
addObserver: (cb: (exit: Exit.Exit<unknown, unknown>) => void) => () => void;
interruptUnsafe: (fiberId?: number | undefined, annotations?: Context.Context<never> | undefined) => void;
pollUnsafe: () => Exit.Exit<unknown, unknown> | undefined;
evaluate: (effect: core.Primitive) => void;
runLoop: (effect: core.Primitive) => typeof core.Yield | Exit.Exit<unknown, unknown>;
getCont: <S extends core.contA | core.contE>(symbol: S) => (core.Primitive & Record<S, (value: any, fiber: effect.FiberImpl) => core.Primitive>) | undefined;
yieldWith: (value: Exit.Exit<any, any> | (() => void)) => core.Yield;
children: () => Set<Fiber.Fiber<any, any>>;
pipe: () => unknown;
setContext: (context: Context.Context<never>) => void;
currentSpanLocal: Span | undefined;
}
FiberImpl<X>(ref: Context.Reference<X>): XgetRef(import effecteffect.const ClockRef: Context.Reference<Clock>const ClockRef: {
key: string;
Service: {
currentTimeMillisUnsafe: () => number;
currentTimeMillis: Effect<number>;
currentTimeNanosUnsafe: () => bigint;
currentTimeNanos: Effect<bigint>;
sleep: (duration: Duration.Duration) => Effect<void>;
};
defaultValue: () => Shape;
of: (this: void, self: Clock) => Clock;
context: (self: Clock) => Context.Context<never>;
use: (f: (service: Clock) => Effect.Effect<A, E, R>) => Effect.Effect<A, E, R>;
useSync: (f: (service: Clock) => A) => Effect.Effect<A, never, never>;
Identifier: Identifier;
stack: string | undefined;
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
toString: () => string;
toJSON: () => unknown;
}
Clock.currentTimeMillisUnsafe(): numberReturns the current time in milliseconds unsafely.
When to use
Use to read millisecond time synchronously when you already have a Clock
service and can accept non-effectful access.
currentTimeMillisUnsafe()
const const fibers: Array<
Fiber.Fiber<unknown, unknown>
>
import ArrArr.const empty: <Fiber.Fiber<unknown, unknown>>() => Fiber.Fiber<unknown, unknown>[]Creates an empty array.
When to use
Use to create a typed empty array without allocating placeholder elements.
Example (Creating an empty array)
import { Array } from "effect"
const result = Array.empty<number>()
console.log(result) // []
empty<import FiberFiber.interface Fiber<out A, out E = never>A runtime fiber is a lightweight thread that executes Effects. Fibers are
the unit of concurrency in Effect. They provide a way to run multiple
Effects concurrently while maintaining structured concurrency and
cancellation safety.
When to use
Use to observe, join, interrupt, or coordinate work that has already been
forked.
Details
A fiber exposes both safe Effect-based operations, such as
await
,
join
, and
interrupt
, and low-level runtime fields used by
the scheduler and runtime internals.
Gotchas
Prefer the exported functions in this module over calling interruptUnsafe
or pollUnsafe directly. The unsafe methods are immediate runtime hooks and
do not provide the same Effect-based sequencing guarantees.
Example (Awaiting a forked fiber)
import { Effect, Fiber } from "effect"
const program = Effect.gen(function*() {
// Fork an effect to run in a new fiber
const fiber = yield* Effect.forkChild(Effect.succeed(42))
// Wait for the fiber to complete and get its result
const result = yield* Fiber.await(fiber)
console.log(result) // Exit.succeed(42)
return result
})
The Fiber namespace contains utility types and functions for working with fibers.
It provides type-level utilities for fiber operations and variance encoding.
When to use
Use to reference type-level helpers associated with Fiber.
Details
The namespace currently exposes type-level support used by the Fiber
interface. Runtime operations are exported as module-level functions.
Example (Working with fiber types)
import { Effect, Fiber } from "effect"
const program = Effect.gen(function*() {
// Create a fiber
const fiber = yield* Effect.forkChild(Effect.succeed(42))
// Use namespace types for variance
const typedFiber: Fiber.Fiber<number, never> = fiber
// Access fiber properties
console.log(`Fiber ID: ${fiber.id}`)
// Join the fiber
const result = yield* Fiber.join(fiber)
return result // 42
})
Fiber<unknown, unknown>>()
const const keys: Key[]keys: interface Array<T>Array<function (type parameter) Key in <Key, A, E, R>(self: ScopedCache<Key, A, E, R>): Effect.Effect<Array<Key>>Key> = []
for (const [const key: Keykey, const entry: Entry<A, E>const entry: {
expiresAt: number | undefined;
deferred: Deferred.Deferred<A, E>;
scope: Scope.Closeable;
}
const state: {
readonly _tag: "Open"
readonly map: MutableHashMap.MutableHashMap<
Key,
Entry<A, E>
>
}
map: MutableHashMap.MutableHashMap<
K,
Entry<A, E>
>
(property) map: {
backing: Map<K, V>;
buckets: Map<number, NonEmptyArray<K>>;
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
toString: () => string;
toJSON: () => unknown;
}
const entry: Entry<A, E>const entry: {
expiresAt: number | undefined;
deferred: Deferred.Deferred<A, E>;
scope: Scope.Closeable;
}
Entry<A, E>.expiresAt: number | undefinedexpiresAt === var undefinedundefined || const entry: Entry<A, E>const entry: {
expiresAt: number | undefined;
deferred: Deferred.Deferred<A, E>;
scope: Scope.Closeable;
}
Entry<A, E>.expiresAt: numberexpiresAt > const now: numbernow) {
const keys: Key[]keys.Array<Key>.push(...items: Key[]): numberAppends new elements to the end of an array, and returns the new length of the array.
push(const key: Keykey)
} else {
import MutableHashMapMutableHashMap.const remove: {
<K>(key: K): <V>(
self: MutableHashMap<K, V>
) => MutableHashMap<K, V>
<K, V>(
self: MutableHashMap<K, V>,
key: K
): MutableHashMap<K, V>
}
const state: {
readonly _tag: "Open"
readonly map: MutableHashMap.MutableHashMap<
Key,
Entry<A, E>
>
}
map: MutableHashMap.MutableHashMap<
K,
Entry<A, E>
>
(property) map: {
backing: Map<K, V>;
buckets: Map<number, NonEmptyArray<K>>;
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
toString: () => string;
toJSON: () => unknown;
}
const key: Keykey)
const fibers: Array<
Fiber.Fiber<unknown, unknown>
>
Array<Fiber<unknown, unknown>>.push(...items: Fiber.Fiber<unknown, unknown>[]): numberAppends new elements to the end of an array, and returns the new length of the array.
push(import effecteffect.const forkUnsafe: <FA, FE, A, E, R>(
parent: Fiber.Fiber<FA, FE>,
effect: Effect.Effect<A, E, R>,
immediate?: boolean,
daemon?: boolean,
uninterruptible?: boolean | "inherit"
) => effect.FiberImpl<A, E>
fiber: effect.FiberImpl<unknown, unknown>(parameter) fiber: {
id: number;
interruptible: boolean;
currentOpCount: number;
currentLoopCount: number;
_stack: Array<Primitive>;
_observers: Array<(exit: Exit.Exit<A, E>) => void>;
_exit: Exit.Exit<A, E> | undefined;
_currentExit: Exit.Exit<A, E> | undefined;
_children: Set<FiberImpl<any, any>> | undefined;
_interruptedCause: Cause.Cause<never> | undefined;
_yielded: Exit.Exit<any, any> | (() => void) | undefined;
context: Context.Context<never>;
currentScheduler: Scheduler.Scheduler;
currentTracerContext: Tracer.Tracer["context"];
currentSpan: Tracer.AnySpan | undefined;
currentLogLevel: LogLevel.LogLevel;
minimumLogLevel: LogLevel.LogLevel;
currentStackFrame: StackFrame | undefined;
runtimeMetrics: Metric.FiberRuntimeMetricsService | undefined;
maxOpsBeforeYield: number;
currentPreventYield: boolean;
_dispatcher: Scheduler.SchedulerDispatcher | undefined;
currentDispatcher: SchedulerDispatcher;
getRef: <X>(ref: Context.Reference<X>) => X;
addObserver: (cb: (exit: Exit.Exit<unknown, unknown>) => void) => () => void;
interruptUnsafe: (fiberId?: number | undefined, annotations?: Context.Context<never> | undefined) => void;
pollUnsafe: () => Exit.Exit<unknown, unknown> | undefined;
evaluate: (effect: core.Primitive) => void;
runLoop: (effect: core.Primitive) => typeof core.Yield | Exit.Exit<unknown, unknown>;
getCont: <S extends core.contA | core.contE>(symbol: S) => (core.Primitive & Record<S, (value: any, fiber: effect.FiberImpl) => core.Primitive>) | undefined;
yieldWith: (value: Exit.Exit<any, any> | (() => void)) => core.Yield;
children: () => Set<Fiber.Fiber<any, any>>;
pipe: () => unknown;
setContext: (context: Context.Context<never>) => void;
currentSpanLocal: Span | undefined;
}
import ScopeScope.const close: <A, E>(
self: Scope,
exit: Exit<A, E>
) => Effect<void>
Closes a scope and runs its registered finalizers.
When to use
Use to close a scope manually with a specific exit value.
Details
Finalizers run in the scope's configured order and receive the supplied
Exit.
Example (Running scope finalizers)
import { Console, Effect, Exit, Scope } from "effect"
const resourceManagement = Effect.gen(function*() {
const scope = yield* Scope.make("sequential")
// Add multiple finalizers
yield* Scope.addFinalizer(scope, Console.log("Close database connection"))
yield* Scope.addFinalizer(scope, Console.log("Close file handle"))
yield* Scope.addFinalizer(scope, Console.log("Release memory"))
// Do some work...
yield* Console.log("Performing operations...")
// Close scope - finalizers run in reverse order of registration
yield* Scope.close(scope, Exit.succeed("Success!"))
// Output: "Release memory", "Close file handle", "Close database connection"
})
close(const entry: Entry<A, E>const entry: {
expiresAt: number | undefined;
deferred: Deferred.Deferred<A, E>;
scope: Scope.Closeable;
}
Entry<A, E>.scope: Scope.Closeable(property) Entry<A, E>.scope: {
strategy: "sequential" | "parallel";
state: State.Open | State.Closed | State.Empty;
}
import effecteffect.const exitVoid: Exit.Exit<void>exitVoid), true, true))
}
}
return const fibers: Array<
Fiber.Fiber<unknown, unknown>
>
Array<T>.length: numberGets or sets the length of the array. This is a number one higher than the highest index in the array.
length === 0 ? import effecteffect.const succeed: <A>(
value: A
) => Effect.Effect<A>
const keys: Key[]keys) : import effecteffect.const as: {
<A, B>(value: B): <E, R>(
self: Effect.Effect<A, E, R>
) => Effect.Effect<B, E, R>
<A, E, R, B>(
self: Effect.Effect<A, E, R>,
value: B
): Effect.Effect<B, E, R>
}
import effecteffect.const fiberAwaitAll: <
Fiber extends Fiber.Fiber<any, any>
>(
self: Iterable<Fiber>
) => Effect.Effect<
Array<
Exit.Exit<
Fiber extends Fiber.Fiber<
infer _A,
infer _E
>
? _A
: never,
Fiber extends Fiber.Fiber<
infer _A,
infer _E
>
? _E
: never
>
>
>
const fibers: Array<
Fiber.Fiber<unknown, unknown>
>
const keys: Key[]keys)
})