Logger.ts overview
Since v2.0.0
Exports Grouped by Category
console
withConsoleError
Signature
declare const withConsoleError: <M, O>(self: Logger<M, O>) => Logger<M, void>
Since v2.0.0
withConsoleLog
Signature
declare const withConsoleLog: <M, O>(self: Logger<M, O>) => Logger<M, void>
Since v2.0.0
withLeveledConsole
Takes a Logger<M, O> and returns a logger that calls the respective Console method based on the log level.
Example
import { Logger, Effect } from "effect"
const loggerLayer = Logger.replace(Logger.defaultLogger, Logger.withLeveledConsole(Logger.stringLogger))
Effect.gen(function* () {
yield* Effect.logError("an error")
yield* Effect.logInfo("an info")
}).pipe(Effect.provide(loggerLayer))
Signature
declare const withLeveledConsole: <M, O>(self: Logger<M, O>) => Logger<M, void>
Since v3.8.0
constructors
defaultLogger
Signature
declare const defaultLogger: Logger<unknown, void>
Since v2.0.0
json
The json logger formats log entries as JSON objects, making them easy to integrate with logging systems that consume JSON data.
Example
import { Effect, Logger } from "effect"
const program = Effect.log("message1", "message2").pipe(
Effect.annotateLogs({ key1: "value1", key2: "value2" }),
Effect.withLogSpan("myspan")
)
Effect.runFork(program.pipe(Effect.provide(Logger.json)))
// {"message":["message1","message2"],"logLevel":"INFO","timestamp":"...","annotations":{"key2":"value2","key1":"value1"},"spans":{"myspan":0},"fiberId":"#0"}
Signature
declare const json: Layer.Layer<never, never, never>
Since v2.0.0
jsonLogger
The jsonLogger logger formats log entries as JSON objects, making them easy to integrate with logging systems that consume JSON data.
Example
import { Effect, Logger } from "effect"
const program = Effect.log("message1", "message2").pipe(
Effect.annotateLogs({ key1: "value1", key2: "value2" }),
Effect.withLogSpan("myspan")
)
Effect.runFork(program.pipe(Effect.provide(Logger.json)))
// {"message":["message1","message2"],"logLevel":"INFO","timestamp":"...","annotations":{"key2":"value2","key1":"value1"},"spans":{"myspan":0},"fiberId":"#0"}
Signature
declare const jsonLogger: Logger<unknown, string>
Since v2.0.0
logFmt
This logger outputs logs in a human-readable format that is easy to read during development or in a production console.
Example
import { Effect, Logger } from "effect"
const program = Effect.log("message1", "message2").pipe(
Effect.annotateLogs({ key1: "value1", key2: "value2" }),
Effect.withLogSpan("myspan")
)
Effect.runFork(program.pipe(Effect.provide(Logger.logFmt)))
// timestamp=... level=INFO fiber=#0 message=message1 message=message2 myspan=0ms key2=value2 key1=value1
Signature
declare const logFmt: Layer.Layer<never, never, never>
Since v2.0.0
logfmtLogger
This logger outputs logs in a human-readable format that is easy to read during development or in a production console.
Example
import { Effect, Logger } from "effect"
const program = Effect.log("message1", "message2").pipe(
Effect.annotateLogs({ key1: "value1", key2: "value2" }),
Effect.withLogSpan("myspan")
)
Effect.runFork(program.pipe(Effect.provide(Logger.logFmt)))
// timestamp=... level=INFO fiber=#0 message=message1 message=message2 myspan=0ms key2=value2 key1=value1
Signature
declare const logfmtLogger: Logger<unknown, string>
Since v2.0.0
make
Creates a custom logger that formats log messages according to the provided function.
Example
import { Effect, Logger, LogLevel } from "effect"
const logger = Logger.make(({ logLevel, message }) => {
globalThis.console.log(`[${logLevel.label}] ${message}`)
})
const task1 = Effect.logDebug("task1 done")
const task2 = Effect.logDebug("task2 done")
const program = Effect.gen(function* () {
yield* Effect.log("start")
yield* task1
yield* task2
yield* Effect.log("done")
}).pipe(Logger.withMinimumLogLevel(LogLevel.Debug), Effect.provide(Logger.replace(Logger.defaultLogger, logger)))
Effect.runFork(program)
// [INFO] start
// [DEBUG] task1 done
// [DEBUG] task2 done
// [INFO] done
Signature
declare const make: <Message, Output>(log: (options: Logger.Options<Message>) => Output) => Logger<Message, Output>
Since v2.0.0
none
A logger that does nothing in response to logging events.
Signature
declare const none: Logger<unknown, void>
Since v2.0.0
pretty
The pretty logger utilizes the capabilities of the console API to generate visually engaging and color-enhanced log outputs. This feature is particularly useful for improving the readability of log messages during development and debugging processes.
Example
import { Effect, Logger } from "effect"
const program = Effect.log("message1", "message2").pipe(
Effect.annotateLogs({ key1: "value1", key2: "value2" }),
Effect.withLogSpan("myspan")
)
Effect.runFork(program.pipe(Effect.provide(Logger.pretty)))
// green --v v-- bold and cyan
// [07:51:54.434] INFO (#0) myspan=1ms: message1
// message2
// v-- bold
// key2: value2
// key1: value1
Signature
declare const pretty: Layer.Layer<never, never, never>
Since v3.5.0
prettyLogger
The pretty logger utilizes the capabilities of the console API to generate visually engaging and color-enhanced log outputs. This feature is particularly useful for improving the readability of log messages during development and debugging processes.
Example
import { Effect, Logger } from "effect"
const program = Effect.log("message1", "message2").pipe(
Effect.annotateLogs({ key1: "value1", key2: "value2" }),
Effect.withLogSpan("myspan")
)
Effect.runFork(program.pipe(Effect.provide(Logger.pretty)))
// green --v v-- bold and cyan
// [07:51:54.434] INFO (#0) myspan=1ms: message1
// message2
// v-- bold
// key2: value2
// key1: value1
Signature
declare const prettyLogger: (options?: {
readonly colors?: "auto" | boolean | undefined
readonly stderr?: boolean | undefined
readonly formatDate?: ((date: Date) => string) | undefined
readonly mode?: "browser" | "tty" | "auto" | undefined
}) => Logger<unknown, void>
Since v3.5.0
prettyLoggerDefault
A default version of the pretty logger.
Signature
declare const prettyLoggerDefault: Logger<unknown, void>
Since v3.8.0
simple
Signature
declare const simple: <A, B>(log: (a: A) => B) => Logger<A, B>
Since v2.0.0
stringLogger
Signature
declare const stringLogger: Logger<unknown, string>
Since v2.0.0
structured
The structured logger provides detailed log outputs, structured in a way that retains comprehensive traceability of the events, suitable for deeper analysis and troubleshooting.
Example
import { Effect, Logger } from "effect"
const program = Effect.log("message1", "message2").pipe(
Effect.annotateLogs({ key1: "value1", key2: "value2" }),
Effect.withLogSpan("myspan")
)
Effect.runFork(program.pipe(Effect.provide(Logger.structured)))
// {
// message: [ 'message1', 'message2' ],
// logLevel: 'INFO',
// timestamp: '2024-07-09T14:05:41.623Z',
// cause: undefined,
// annotations: { key2: 'value2', key1: 'value1' },
// spans: { myspan: 0 },
// fiberId: '#0'
// }
Signature
declare const structured: Layer.Layer<never, never, never>
Since v2.0.0
structuredLogger
The structured logger provides detailed log outputs, structured in a way that retains comprehensive traceability of the events, suitable for deeper analysis and troubleshooting.
Example
import { Effect, Logger } from "effect"
const program = Effect.log("message1", "message2").pipe(
Effect.annotateLogs({ key1: "value1", key2: "value2" }),
Effect.withLogSpan("myspan")
)
Effect.runFork(program.pipe(Effect.provide(Logger.structured)))
// {
// message: [ 'message1', 'message2' ],
// logLevel: 'INFO',
// timestamp: '2024-07-09T14:05:41.623Z',
// cause: undefined,
// annotations: { key2: 'value2', key1: 'value1' },
// spans: { myspan: 0 },
// fiberId: '#0'
// }
Signature
declare const structuredLogger: Logger<
unknown,
{
readonly logLevel: string
readonly fiberId: string
readonly timestamp: string
readonly message: unknown
readonly cause: string | undefined
readonly annotations: Record<string, unknown>
readonly spans: Record<string, number>
}
>
Since v2.0.0
succeed
Signature
declare const succeed: <A>(value: A) => Logger<unknown, A>
Since v2.0.0
sync
Signature
declare const sync: <A>(evaluate: LazyArg<A>) => Logger<unknown, A>
Since v2.0.0
test
Signature
declare const test: {
<Message>(input: Message): <Output>(self: Logger<Message, Output>) => Output
<Message, Output>(self: Logger<Message, Output>, input: Message): Output
}
Since v2.0.0
tracerLogger
Signature
declare const tracerLogger: Logger<unknown, void>
Since v2.0.0
context
add
Signature
declare const add: <B>(logger: Logger<unknown, B>) => Layer.Layer<never>
Since v2.0.0
addEffect
Signature
declare const addEffect: <A, E, R>(effect: Effect<Logger<unknown, A>, E, R>) => Layer.Layer<never, E, R>
Since v2.0.0
addScoped
Signature
declare const addScoped: <A, E, R>(effect: Effect<Logger<unknown, A>, E, R>) => Layer.Layer<never, E, Exclude<R, Scope>>
Since v2.0.0
minimumLogLevel
Sets the minimum log level for logging operations, allowing control over which log messages are displayed based on their severity.
Example
import { Effect, Logger, LogLevel } from "effect"
const program = Effect.gen(function* () {
yield* Effect.log("Executing task...")
yield* Effect.sleep("100 millis")
console.log("task done")
})
// Logging disabled using a layer
Effect.runFork(program.pipe(Effect.provide(Logger.minimumLogLevel(LogLevel.None))))
// task done
Signature
declare const minimumLogLevel: (level: LogLevel.LogLevel) => Layer.Layer<never>
Since v2.0.0
remove
Signature
declare const remove: <A>(logger: Logger<unknown, A>) => Layer.Layer<never>
Since v2.0.0
replace
Signature
declare const replace: {
<B>(that: Logger<unknown, B>): <A>(self: Logger<unknown, A>) => Layer.Layer<never>
<A, B>(self: Logger<unknown, A>, that: Logger<unknown, B>): Layer.Layer<never>
}
Since v2.0.0
replaceEffect
Signature
declare const replaceEffect: {
<B, E, R>(that: Effect<Logger<unknown, B>, E, R>): <A>(self: Logger<unknown, A>) => Layer.Layer<never, E, R>
<A, B, E, R>(self: Logger<unknown, A>, that: Effect<Logger<unknown, B>, E, R>): Layer.Layer<never, E, R>
}
Since v2.0.0
replaceScoped
Signature
declare const replaceScoped: {
<B, E, R>(
that: Effect<Logger<unknown, B>, E, R>
): <A>(self: Logger<unknown, A>) => Layer.Layer<never, E, Exclude<R, Scope>>
<A, B, E, R>(
self: Logger<unknown, A>,
that: Effect<Logger<unknown, B>, E, R>
): Layer.Layer<never, E, Exclude<R, Scope>>
}
Since v2.0.0
withMinimumLogLevel
Sets the minimum log level for subsequent logging operations, allowing control over which log messages are displayed based on their severity.
Example
import { Effect, Logger, LogLevel } from "effect"
const program = Effect.logDebug("message1").pipe(Logger.withMinimumLogLevel(LogLevel.Debug))
Effect.runFork(program)
// timestamp=... level=DEBUG fiber=#0 message=message1
Signature
declare const withMinimumLogLevel: {
(level: LogLevel.LogLevel): <A, E, R>(self: Effect<A, E, R>) => Effect<A, E, R>
<A, E, R>(self: Effect<A, E, R>, level: LogLevel.LogLevel): Effect<A, E, R>
}
Since v2.0.0
filtering
filterLogLevel
Returns a version of this logger that only logs messages when the log level satisfies the specified predicate.
Signature
declare const filterLogLevel: {
(
f: (logLevel: LogLevel.LogLevel) => boolean
): <Message, Output>(self: Logger<Message, Output>) => Logger<Message, Option.Option<Output>>
<Message, Output>(
self: Logger<Message, Output>,
f: (logLevel: LogLevel.LogLevel) => boolean
): Logger<Message, Option.Option<Output>>
}
Since v2.0.0
guards
isLogger
Returns true if the specified value is a Logger, otherwise returns false.
Signature
declare const isLogger: (u: unknown) => u is Logger<unknown, unknown>
Since v1.0.0
mapping
batched
Creates a batched logger that groups log messages together and processes them in intervals.
Example
import { Console, Effect, Logger } from "effect"
const LoggerLive = Logger.replaceScoped(
Logger.defaultLogger,
Logger.logfmtLogger.pipe(
Logger.batched("500 millis", (messages) => Console.log("BATCH", `[\n${messages.join("\n")}\n]`))
)
)
const program = Effect.gen(function* () {
yield* Effect.log("one")
yield* Effect.log("two")
yield* Effect.log("three")
}).pipe(Effect.provide(LoggerLive))
Effect.runFork(program)
// BATCH [
// timestamp=... level=INFO fiber=#0 message=one
// timestamp=... level=INFO fiber=#0 message=two
// timestamp=... level=INFO fiber=#0 message=three
// ]
Signature
declare const batched: {
<Output, R>(
window: DurationInput,
f: (messages: Array<Types.NoInfer<Output>>) => Effect<void, never, R>
): <Message>(self: Logger<Message, Output>) => Effect<Logger<Message, void>, never, R | Scope>
<Message, Output, R>(
self: Logger<Message, Output>,
window: DurationInput,
f: (messages: Array<Types.NoInfer<Output>>) => Effect<void, never, R>
): Effect<Logger<Message, void>, never, Scope | R>
}
Since v2.0.0
map
Signature
declare const map: {
<Output, Output2>(
f: (output: Output) => Output2
): <Message>(self: Logger<Message, Output>) => Logger<Message, Output2>
<Message, Output, Output2>(self: Logger<Message, Output>, f: (output: Output) => Output2): Logger<Message, Output2>
}
Since v2.0.0
mapInput
Signature
declare const mapInput: {
<Message, Message2>(
f: (message: Message2) => Message
): <Output>(self: Logger<Message, Output>) => Logger<Message2, Output>
<Output, Message, Message2>(
self: Logger<Message, Output>,
f: (message: Message2) => Message
): Logger<Message2, Output>
}
Since v2.0.0
mapInputOptions
Signature
declare const mapInputOptions: {
<Message, Message2>(
f: (options: Logger.Options<Message2>) => Logger.Options<Message>
): <Output>(self: Logger<Message, Output>) => Logger<Message2, Output>
<Output, Message, Message2>(
self: Logger<Message, Output>,
f: (options: Logger.Options<Message2>) => Logger.Options<Message>
): Logger<Message2, Output>
}
Since v2.0.0
models
Logger (interface)
Signature
export interface Logger<in Message, out Output> extends Logger.Variance<Message, Output>, Pipeable {
log(options: Logger.Options<Message>): Output
}
Since v2.0.0
symbols
LoggerTypeId
Signature
declare const LoggerTypeId: unique symbol
Since v2.0.0
LoggerTypeId (type alias)
Signature
type LoggerTypeId = typeof LoggerTypeId
Since v2.0.0
tracing
withSpanAnnotations
Signature
declare const withSpanAnnotations: <Message, Output>(self: Logger<Message, Output>) => Logger<Message, Output>
Since v2.0.0
utils
Logger (namespace)
Since v2.0.0
Variance (interface)
Signature
export interface Variance<in Message, out Output> {
readonly [LoggerTypeId]: {
readonly _Message: Types.Contravariant<Message>
readonly _Output: Types.Covariant<Output>
}
}
Since v2.0.0
Options (interface)
Signature
export interface Options<out Message> {
readonly fiberId: FiberId.FiberId
readonly logLevel: LogLevel.LogLevel
readonly message: Message
readonly cause: Cause.Cause<unknown>
readonly context: FiberRefs.FiberRefs
readonly spans: List.List<LogSpan.LogSpan>
readonly annotations: HashMap.HashMap<string, unknown>
readonly date: Date
}
Since v2.0.0
zipping
zip
Combines this logger with the specified logger to produce a new logger that logs to both this logger and that logger.
Signature
declare const zip: {
<Message2, Output2>(
that: Logger<Message2, Output2>
): <Message, Output>(self: Logger<Message, Output>) => Logger<Message & Message2, [Output, Output2]>
<Message, Output, Message2, Output2>(
self: Logger<Message, Output>,
that: Logger<Message2, Output2>
): Logger<Message & Message2, [Output, Output2]>
}
Since v2.0.0
zipLeft
Signature
declare const zipLeft: {
<Message2, Output2>(
that: Logger<Message2, Output2>
): <Message, Output>(self: Logger<Message, Output>) => Logger<Message & Message2, Output>
<Message, Output, Message2, Output2>(
self: Logger<Message, Output>,
that: Logger<Message2, Output2>
): Logger<Message & Message2, Output>
}
Since v2.0.0
zipRight
Signature
declare const zipRight: {
<Message2, Output2>(
that: Logger<Message2, Output2>
): <Message, Output>(self: Logger<Message, Output>) => Logger<Message & Message2, Output2>
<Message, Output, Message2, Output2>(
self: Logger<Message, Output>,
that: Logger<Message2, Output2>
): Logger<Message & Message2, Output2>
}
Since v2.0.0