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effect

Pool overview

Added in v2.0.0

Table of contents

combinators

invalidate

Invalidates the specified item. This will cause the pool to eventually reallocate the item, although this reallocation may occur lazily rather than eagerly.

Signature

export declare const invalidate: {
  <A>(value: A): <E>(self: Pool<A, E>) => Effect.Effect<void, never, Scope.Scope>
  <A, E>(self: Pool<A, E>, value: A): Effect.Effect<void, never, Scope.Scope>
}

Added in v2.0.0

constructors

make

Makes a new pool of the specified fixed size. The pool is returned in a Scope, which governs the lifetime of the pool. When the pool is shutdown because the Scope is closed, the individual items allocated by the pool will be released in some unspecified order.

By setting the concurrency parameter, you can control the level of concurrent access per pool item. By default, the number of permits is set to 1.

targetUtilization determines when to create new pool items. It is a value between 0 and 1, where 1 means only create new pool items when all the existing items are fully utilized.

A targetUtilization of 0.5 will create new pool items when the existing items are 50% utilized.

Signature

export declare const make: <A, E, R>(options: {
  readonly acquire: Effect.Effect<A, E, R>
  readonly size: number
  readonly concurrency?: number | undefined
  readonly targetUtilization?: number | undefined
}) => Effect.Effect<Pool<A, E>, never, Scope.Scope | R>

Added in v2.0.0

makeWithTTL

Makes a new pool with the specified minimum and maximum sizes and time to live before a pool whose excess items are not being used will be shrunk down to the minimum size. The pool is returned in a Scope, which governs the lifetime of the pool. When the pool is shutdown because the Scope is used, the individual items allocated by the pool will be released in some unspecified order.

By setting the concurrency parameter, you can control the level of concurrent access per pool item. By default, the number of permits is set to 1.

targetUtilization determines when to create new pool items. It is a value between 0 and 1, where 1 means only create new pool items when all the existing items are fully utilized.

A targetUtilization of 0.5 will create new pool items when the existing items are 50% utilized.

The timeToLiveStrategy determines how items are invalidated. If set to “creation”, then items are invalidated based on their creation time. If set to “usage”, then items are invalidated based on pool usage.

By default, the timeToLiveStrategy is set to “usage”.

import { createConnection } from "mysql2"
import { Duration, Effect, Pool } from "effect"

const acquireDBConnection = Effect.acquireRelease(
  Effect.sync(() => createConnection("mysql://...")),
  (connection) => Effect.sync(() => connection.end(() => {}))
)

const connectionPool = Effect.flatMap(
  Pool.makeWithTTL({
    acquire: acquireDBConnection,
    min: 10,
    max: 20,
    timeToLive: Duration.seconds(60)
  }),
  (pool) => pool.get
)

Signature

export declare const makeWithTTL: <A, E, R>(options: {
  readonly acquire: Effect.Effect<A, E, R>
  readonly min: number
  readonly max: number
  readonly concurrency?: number | undefined
  readonly targetUtilization?: number | undefined
  readonly timeToLive: Duration.DurationInput
  readonly timeToLiveStrategy?: "creation" | "usage" | undefined
}) => Effect.Effect<Pool<A, E>, never, Scope.Scope | R>

Added in v2.0.0

getters

get

Retrieves an item from the pool in a scoped effect. Note that if acquisition fails, then the returned effect will fail for that same reason. Retrying a failed acquisition attempt will repeat the acquisition attempt.

Signature

export declare const get: <A, E>(self: Pool<A, E>) => Effect.Effect<A, E, Scope.Scope>

Added in v2.0.0

models

Pool (interface)

A Pool<A, E> is a pool of items of type A, each of which may be associated with the acquisition and release of resources. An attempt to get an item A from a pool may fail with an error of type E.

Signature

export interface Pool<in out A, out E = never> extends Pool.Variance<A, E>, Effect.Effect<A, E, Scope.Scope>, Pipeable {
  /**
   * Retrieves an item from the pool in a scoped effect. Note that if
   * acquisition fails, then the returned effect will fail for that same reason.
   * Retrying a failed acquisition attempt will repeat the acquisition attempt.
   */
  readonly get: Effect.Effect<A, E, Scope.Scope>

  /**
   * Invalidates the specified item. This will cause the pool to eventually
   * reallocate the item, although this reallocation may occur lazily rather
   * than eagerly.
   */
  invalidate(item: A): Effect.Effect<void>

  readonly [Unify.typeSymbol]?: unknown
  readonly [Unify.unifySymbol]?: PoolUnify<this>
  readonly [Unify.ignoreSymbol]?: PoolUnifyIgnore
}

Added in v2.0.0

PoolUnify (interface)

Signature

export interface PoolUnify<A extends { [Unify.typeSymbol]?: any }> extends Effect.EffectUnify<A> {
  Pool?: () => Extract<A[Unify.typeSymbol], Pool<any, any>> extends Pool<infer A0, infer _E0> | infer _
    ? A0 extends any
      ? Extract<A[Unify.typeSymbol], Pool<A0, any>> extends Pool<A0, infer E1>
        ? Pool<A0, E1>
        : never
      : never
    : never
}

Added in v3.9.0

PoolUnifyIgnore (interface)

Signature

export interface PoolUnifyIgnore extends Effect.EffectUnifyIgnore {
  Effect?: true
}

Added in v3.9.0

refinements

isPool

Returns true if the specified value is a Pool, false otherwise.

Signature

export declare const isPool: (u: unknown) => u is Pool<unknown, unknown>

Added in v2.0.0

symbols

PoolTypeId

Signature

export declare const PoolTypeId: typeof PoolTypeId

Added in v2.0.0

PoolTypeId (type alias)

Signature

export type PoolTypeId = typeof PoolTypeId

Added in v2.0.0

utils

Pool (namespace)

Added in v2.0.0

Variance (interface)

Signature

export interface Variance<in out A, out E> {
  readonly [PoolTypeId]: {
    readonly _A: Types.Invariant<A>
    readonly _E: Types.Covariant<E>
  }
}

Added in v2.0.0