Context.Reference<
ReadonlyArray<[label: string, timestamp: number]>
>Context reference for managing log spans that track the duration and hierarchy of operations. Each span represents a labeled time period for performance analysis and debugging.
When to use
Use to carry the active log span stack that should be included with log entries in the current context.
Example (Tracking log spans)
import { Console, Effect, References } from "effect"
const logSpanExample = Effect.gen(function*() {
// Get current spans (empty by default)
const current = yield* References.CurrentLogSpans
console.log(current.length) // 0
// Add a log span manually
const databaseConnectionStartedAt = 0
yield* Effect.provideService(
Effect.gen(function*() {
// Simulate some work
yield* Effect.sleep("100 millis")
yield* Console.log("Database operation in progress")
const spans = yield* References.CurrentLogSpans
console.log("Active spans:", spans.map(([label]) => label)) // ["database-connection"]
}),
References.CurrentLogSpans,
[["database-connection", databaseConnectionStartedAt]]
)
// Add another span
const dataProcessingStartedAt = 100
yield* Effect.provideService(
Effect.gen(function*() {
const spans = yield* References.CurrentLogSpans
console.log("Active spans:", spans.map(([label]) => label)) // ["database-connection", "data-processing"]
yield* Console.log("Multiple operations in progress")
}),
References.CurrentLogSpans,
[
["database-connection", databaseConnectionStartedAt],
["data-processing", dataProcessingStartedAt]
]
)
// Clear spans when operations complete
yield* Effect.provideService(
Effect.gen(function*() {
const spans = yield* References.CurrentLogSpans
console.log("Active spans:", spans.length) // 0
}),
References.CurrentLogSpans,
[]
)
})export const const CurrentLogSpans: Context.Reference<
ReadonlyArray<
[label: string, timestamp: number]
>
>
const CurrentLogSpans: {
key: string;
Service: {
length: number;
toString: () => string;
toLocaleString: { (): string; (locales: string | string[], options?: Intl.NumberFormatOptions & Intl.DateTimeFormatOptions): string };
concat: { (...items: Array<ConcatArray<[label: string, timestamp: number]>>): Array<[label: string, timestamp: number]>; (...items: Array<[label: string, timestamp: number] | ConcatArray<[label: string, timestamp: number]>>): Array<[label: string,…;
join: (separator?: string) => string;
slice: (start?: number, end?: number) => Array<[label: string, timestamp: number]>;
indexOf: (searchElement: [label: string, timestamp: number], fromIndex?: number) => number;
lastIndexOf: (searchElement: [label: string, timestamp: number], fromIndex?: number) => number;
every: { (predicate: (value: [label: string, timestamp: number], index: number, array: ReadonlyArray<[label: string, timestamp: number]>) => value is S, thisArg?: any): this is readonly S[]; (predicate: (value: [label: string, timestamp: number],…;
some: (predicate: (value: [label: string, timestamp: number], index: number, array: ReadonlyArray<[label: string, timestamp: number]>) => unknown, thisArg?: any) => boolean;
forEach: (callbackfn: (value: [label: string, timestamp: number], index: number, array: ReadonlyArray<[label: string, timestamp: number]>) => void, thisArg?: any) => void;
map: (callbackfn: (value: [label: string, timestamp: number], index: number, array: ReadonlyArray<[label: string, timestamp: number]>) => U, thisArg?: any) => Array<U>;
filter: { (predicate: (value: [label: string, timestamp: number], index: number, array: ReadonlyArray<[label: string, timestamp: number]>) => value is S, thisArg?: any): Array<S>; (predicate: (value: [label: string, timestamp: number], index: numb…;
reduce: { (callbackfn: (previousValue: [label: string, timestamp: number], currentValue: [label: string, timestamp: number], currentIndex: number, array: ReadonlyArray<[label: string, timestamp: number]>) => [label: string, timestamp: number]): [l…;
reduceRight: { (callbackfn: (previousValue: [label: string, timestamp: number], currentValue: [label: string, timestamp: number], currentIndex: number, array: ReadonlyArray<[label: string, timestamp: number]>) => [label: string, timestamp: number]): [l…;
find: { (predicate: (value: [label: string, timestamp: number], index: number, obj: ReadonlyArray<[label: string, timestamp: number]>) => value is S, thisArg?: any): S | undefined; (predicate: (value: [label: string, timestamp: number], index: n…;
findIndex: (predicate: (value: [label: string, timestamp: number], index: number, obj: ReadonlyArray<[label: string, timestamp: number]>) => unknown, thisArg?: any) => number;
entries: () => ArrayIterator<[number, [label: string, timestamp: number]]>;
keys: () => ArrayIterator<number>;
values: () => ArrayIterator<[label: string, timestamp: number]>;
includes: (searchElement: [label: string, timestamp: number], fromIndex?: number) => boolean;
flatMap: (callback: (this: This, value: [label: string, timestamp: number], index: number, array: Array<[label: string, timestamp: number]>) => U | ReadonlyArray<U>, thisArg?: This | undefined) => Array<U>;
flat: (this: A, depth?: D | undefined) => Array<FlatArray<A, D>>;
at: (index: number) => [label: string, timestamp: number] | undefined;
findLast: { (predicate: (value: [label: string, timestamp: number], index: number, array: ReadonlyArray<[label: string, timestamp: number]>) => value is S, thisArg?: any): S | undefined; (predicate: (value: [label: string, timestamp: number], index:…;
findLastIndex: (predicate: (value: [label: string, timestamp: number], index: number, array: ReadonlyArray<[label: string, timestamp: number]>) => unknown, thisArg?: any) => number;
toReversed: () => Array<[label: string, timestamp: number]>;
toSorted: (compareFn?: ((a: [label: string, timestamp: number], b: [label: string, timestamp: number]) => number) | undefined) => Array<[label: string, timestamp: number]>;
toSpliced: { (start: number, deleteCount: number, ...items: Array<[label: string, timestamp: number]>): Array<[label: string, timestamp: number]>; (start: number, deleteCount?: number): Array<[label: string, timestamp: number]> };
with: (index: number, value: [label: string, timestamp: number]) => Array<[label: string, timestamp: number]>;
};
defaultValue: () => Shape;
of: (this: void, self: ReadonlyArray<[label: string, timestamp: number]>) => ReadonlyArray<[label: string, timestamp: number]>;
context: (self: ReadonlyArray<[label: string, timestamp: number]>) => Context.Context<never>;
use: (f: (service: ReadonlyArray<[label: string, timestamp: number]>) => Effect<A, E, R>) => Effect<A, E, R>;
useSync: (f: (service: ReadonlyArray<[label: string, timestamp: number]>) => A) => 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;
}
Context reference for managing log spans that track the duration and hierarchy of operations.
Each span represents a labeled time period for performance analysis and debugging.
When to use
Use to carry the active log span stack that should be included with log
entries in the current context.
Example (Tracking log spans)
import { Console, Effect, References } from "effect"
const logSpanExample = Effect.gen(function*() {
// Get current spans (empty by default)
const current = yield* References.CurrentLogSpans
console.log(current.length) // 0
// Add a log span manually
const databaseConnectionStartedAt = 0
yield* Effect.provideService(
Effect.gen(function*() {
// Simulate some work
yield* Effect.sleep("100 millis")
yield* Console.log("Database operation in progress")
const spans = yield* References.CurrentLogSpans
console.log("Active spans:", spans.map(([label]) => label)) // ["database-connection"]
}),
References.CurrentLogSpans,
[["database-connection", databaseConnectionStartedAt]]
)
// Add another span
const dataProcessingStartedAt = 100
yield* Effect.provideService(
Effect.gen(function*() {
const spans = yield* References.CurrentLogSpans
console.log("Active spans:", spans.map(([label]) => label)) // ["database-connection", "data-processing"]
yield* Console.log("Multiple operations in progress")
}),
References.CurrentLogSpans,
[
["database-connection", databaseConnectionStartedAt],
["data-processing", dataProcessingStartedAt]
]
)
// Clear spans when operations complete
yield* Effect.provideService(
Effect.gen(function*() {
const spans = yield* References.CurrentLogSpans
console.log("Active spans:", spans.length) // 0
}),
References.CurrentLogSpans,
[]
)
})
CurrentLogSpans: import ContextContext.interface Reference<in out Shape>Service key with a lazily computed default value.
Details
When a Reference is requested from a Context that does not contain an
override, Context getters that resolve references return the cached default
value instead of failing.
Example (Defining a reference with a default value)
import { Context } from "effect"
// Define a reference with a default value
const LoggerRef: Context.Reference<{ log: (msg: string) => void }> =
Context.Reference("Logger", {
defaultValue: () => ({ log: (msg: string) => console.log(msg) })
})
// The reference can be used without explicit provision
const context = Context.empty()
const logger = Context.get(context, LoggerRef) // Uses default value
Creates a context key with a default value.
When to use
Use when you need to define a context key with a lazily computed default
value.
Details
Context.Reference allows you to create a key that can hold a value. You
can provide a default value for the service, which will automatically be used
when the context is accessed, or override it with a custom implementation
when needed. The default value is computed lazily and cached on the
reference.
Example (Creating references with default values)
import { Context } from "effect"
// Create a reference with a default value
const LoggerRef = Context.Reference("Logger", {
defaultValue: () => ({ log: (msg: string) => console.log(msg) })
})
// The reference provides the default value when accessed from an empty context
const context = Context.empty()
const logger = Context.get(context, LoggerRef)
// You can also override the default value
const customContext = Context.make(LoggerRef, {
log: (msg: string) => `Custom: ${msg}`
})
const customLogger = Context.get(customContext, LoggerRef)
Reference<interface ReadonlyArray<T>ReadonlyArray<[stringlabel: string, numbertimestamp: number]>> =
import referencesreferences.const CurrentLogSpans: Context.Reference<
ReadonlyArray<
[label: string, timestamp: number]
>
>
const CurrentLogSpans: {
key: string;
Service: {
length: number;
toString: () => string;
toLocaleString: { (): string; (locales: string | string[], options?: Intl.NumberFormatOptions & Intl.DateTimeFormatOptions): string };
concat: { (...items: Array<ConcatArray<[label: string, timestamp: number]>>): Array<[label: string, timestamp: number]>; (...items: Array<[label: string, timestamp: number] | ConcatArray<[label: string, timestamp: number]>>): Array<[label: string,…;
join: (separator?: string) => string;
slice: (start?: number, end?: number) => Array<[label: string, timestamp: number]>;
indexOf: (searchElement: [label: string, timestamp: number], fromIndex?: number) => number;
lastIndexOf: (searchElement: [label: string, timestamp: number], fromIndex?: number) => number;
every: { (predicate: (value: [label: string, timestamp: number], index: number, array: ReadonlyArray<[label: string, timestamp: number]>) => value is S, thisArg?: any): this is readonly S[]; (predicate: (value: [label: string, timestamp: number],…;
some: (predicate: (value: [label: string, timestamp: number], index: number, array: ReadonlyArray<[label: string, timestamp: number]>) => unknown, thisArg?: any) => boolean;
forEach: (callbackfn: (value: [label: string, timestamp: number], index: number, array: ReadonlyArray<[label: string, timestamp: number]>) => void, thisArg?: any) => void;
map: (callbackfn: (value: [label: string, timestamp: number], index: number, array: ReadonlyArray<[label: string, timestamp: number]>) => U, thisArg?: any) => Array<U>;
filter: { (predicate: (value: [label: string, timestamp: number], index: number, array: ReadonlyArray<[label: string, timestamp: number]>) => value is S, thisArg?: any): Array<S>; (predicate: (value: [label: string, timestamp: number], index: numb…;
reduce: { (callbackfn: (previousValue: [label: string, timestamp: number], currentValue: [label: string, timestamp: number], currentIndex: number, array: ReadonlyArray<[label: string, timestamp: number]>) => [label: string, timestamp: number]): [l…;
reduceRight: { (callbackfn: (previousValue: [label: string, timestamp: number], currentValue: [label: string, timestamp: number], currentIndex: number, array: ReadonlyArray<[label: string, timestamp: number]>) => [label: string, timestamp: number]): [l…;
find: { (predicate: (value: [label: string, timestamp: number], index: number, obj: ReadonlyArray<[label: string, timestamp: number]>) => value is S, thisArg?: any): S | undefined; (predicate: (value: [label: string, timestamp: number], index: n…;
findIndex: (predicate: (value: [label: string, timestamp: number], index: number, obj: ReadonlyArray<[label: string, timestamp: number]>) => unknown, thisArg?: any) => number;
entries: () => ArrayIterator<[number, [label: string, timestamp: number]]>;
keys: () => ArrayIterator<number>;
values: () => ArrayIterator<[label: string, timestamp: number]>;
includes: (searchElement: [label: string, timestamp: number], fromIndex?: number) => boolean;
flatMap: (callback: (this: This, value: [label: string, timestamp: number], index: number, array: Array<[label: string, timestamp: number]>) => U | ReadonlyArray<U>, thisArg?: This | undefined) => Array<U>;
flat: (this: A, depth?: D | undefined) => Array<FlatArray<A, D>>;
at: (index: number) => [label: string, timestamp: number] | undefined;
findLast: { (predicate: (value: [label: string, timestamp: number], index: number, array: ReadonlyArray<[label: string, timestamp: number]>) => value is S, thisArg?: any): S | undefined; (predicate: (value: [label: string, timestamp: number], index:…;
findLastIndex: (predicate: (value: [label: string, timestamp: number], index: number, array: ReadonlyArray<[label: string, timestamp: number]>) => unknown, thisArg?: any) => number;
toReversed: () => Array<[label: string, timestamp: number]>;
toSorted: (compareFn?: ((a: [label: string, timestamp: number], b: [label: string, timestamp: number]) => number) | undefined) => Array<[label: string, timestamp: number]>;
toSpliced: { (start: number, deleteCount: number, ...items: Array<[label: string, timestamp: number]>): Array<[label: string, timestamp: number]>; (start: number, deleteCount?: number): Array<[label: string, timestamp: number]> };
with: (index: number, value: [label: string, timestamp: number]) => Array<[label: string, timestamp: number]>;
};
defaultValue: () => Shape;
of: (this: void, self: ReadonlyArray<[label: string, timestamp: number]>) => ReadonlyArray<[label: string, timestamp: number]>;
context: (self: ReadonlyArray<[label: string, timestamp: number]>) => Context.Context<never>;
use: (f: (service: ReadonlyArray<[label: string, timestamp: number]>) => Effect<A, E, R>) => Effect<A, E, R>;
useSync: (f: (service: ReadonlyArray<[label: string, timestamp: number]>) => A) => 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;
}
CurrentLogSpans