Schedules define stateful, possibly effectful, recurring schedules of events, and compose in a variety of ways. Combinators allow us to take schedules and combine them together to get other schedules.
To demonstrate the functionality of different schedules, we will use the following helper function
that logs each repetition along with the corresponding delay in milliseconds, formatted as:
A Schedule<Out, In, R> defines a recurring schedule, which consumes
values of type In, and which returns values of type Out.
Schedules are defined as a possibly infinite set of intervals spread out over
time. Each interval defines a window in which recurrence is possible.
When schedules are used to repeat or retry effects, the starting boundary of
each interval produced by a schedule is used as the moment when the effect
will be executed again.
Schedules compose in the following primary ways:
Union: performs the union of the intervals of two schedules
Intersection: performs the intersection of the intervals of two schedules
Sequence: concatenates the intervals of one schedule onto another
In addition, schedule inputs and outputs can be transformed, filtered (to
terminate a schedule early in response to some input or output), and so
forth.
A variety of other operators exist for transforming and combining schedules,
and the companion object for Schedule contains all common types of
schedules, both for performing retrying, as well as performing repetition.
Converts a Chunk into an Array. If the provided Chunk is non-empty
(NonEmptyChunk), the function will return a NonEmptyArray, ensuring the
non-empty property is preserved.
Executes an effect synchronously, running it immediately and returning the
result.
Details
This function evaluates the provided effect synchronously, returning its
result directly. It is ideal for effects that do not fail or include
asynchronous operations. If the effect does fail or involves async tasks, it
will throw an error. Execution stops at the point of failure or asynchronous
operation, making it unsuitable for effects that require asynchronous
handling.
Important: Attempting to run effects that involve asynchronous operations
or failures will result in exceptions being thrown, so use this function with
care for purely synchronous and error-free effects.
When to Use
Use this function when:
You are sure that the effect will not fail or involve asynchronous
operations.
You need a direct, synchronous result from the effect.
You are working within a context where asynchronous effects are not
allowed.
Avoid using this function for effects that can fail or require asynchronous
handling. For such cases, consider using
runPromise
or
runSyncExit
.
@see ― runSyncExit for a version that returns an Exit type instead of
throwing an error.
@example
// Title: Synchronous Logging
import { Effect } from"effect"
constprogram= Effect.sync(() => {
console.log("Hello, World!")
return1
})
constresult= Effect.runSync(program)
// Output: Hello, World!
console.log(result)
// Output: 1
@example
// Title: Incorrect Usage with Failing or Async Effects
import { Effect } from "effect"
try {
// Attempt to run an effect that fails
Effect.runSync(Effect.fail("my error"))
} catch (e) {
console.error(e)
}
// Output:
// (FiberFailure) Error: my error
try {
// Attempt to run an effect that involves async work
Effect.runSync(Effect.promise(() => Promise.resolve(1)))
} catch (e) {
console.error(e)
}
// Output:
// (FiberFailure) AsyncFiberException: Fiber #0 cannot be resolved synchronously. This is caused by using runSync on an effect that performs async work
Performs the specified action for each element in an array.
@param ― callbackfn A function that accepts up to three arguments. forEach calls the callbackfn function one time for each element in the array.
@param ― thisArg An object to which the this keyword can refer in the callbackfn function. If thisArg is omitted, undefined is used as the this value.
forEach((
duration: Duration.Duration
duration,
i: number
i) => {
18
var console:Console
The console module provides a simple debugging console that is similar to the
JavaScript console mechanism provided by web browsers.
The module exports two specific components:
A Console class with methods such as console.log(), console.error() and console.warn() that can be used to write to any Node.js stream.
A global console instance configured to write to process.stdout and
process.stderr. The global console can be used without importing the node:console module.
Warning: The global console object's methods are neither consistently
synchronous like the browser APIs they resemble, nor are they consistently
asynchronous like all other Node.js streams. See the note on process I/O for
more information.
Example using the global console:
console.log('hello world');
// Prints: hello world, to stdout
console.log('hello %s', 'world');
// Prints: hello world, to stdout
console.error(newError('Whoops, something bad happened'));
// Prints error message and stack trace to stderr:
// Error: Whoops, something bad happened
// at [eval]:5:15
// at Script.runInThisContext (node:vm:132:18)
// at Object.runInThisContext (node:vm:309:38)
// at node:internal/process/execution:77:19
// at [eval]-wrapper:6:22
// at evalScript (node:internal/process/execution:76:60)
// at node:internal/main/eval_string:23:3
constname='Will Robinson';
console.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to stderr
Example using the Console class:
constout=getStreamSomehow();
consterr=getStreamSomehow();
constmyConsole=new console.Console(out, err);
myConsole.log('hello world');
// Prints: hello world, to out
myConsole.log('hello %s', 'world');
// Prints: hello world, to out
myConsole.error(newError('Whoops, something bad happened'));
// Prints: [Error: Whoops, something bad happened], to err
Prints to stdout with newline. Multiple arguments can be passed, with the
first used as the primary message and all additional used as substitution
values similar to printf(3)
(the arguments are all passed to util.format()).
A Schedule<Out, In, R> defines a recurring schedule, which consumes
values of type In, and which returns values of type Out.
Schedules are defined as a possibly infinite set of intervals spread out over
time. Each interval defines a window in which recurrence is possible.
When schedules are used to repeat or retry effects, the starting boundary of
each interval produced by a schedule is used as the moment when the effect
will be executed again.
Schedules compose in the following primary ways:
Union: performs the union of the intervals of two schedules
Intersection: performs the intersection of the intervals of two schedules
Sequence: concatenates the intervals of one schedule onto another
In addition, schedule inputs and outputs can be transformed, filtered (to
terminate a schedule early in response to some input or output), and so
forth.
A variety of other operators exist for transforming and combining schedules,
and the companion object for Schedule contains all common types of
schedules, both for performing retrying, as well as performing repetition.
Converts a Chunk into an Array. If the provided Chunk is non-empty
(NonEmptyChunk), the function will return a NonEmptyArray, ensuring the
non-empty property is preserved.
Executes an effect synchronously, running it immediately and returning the
result.
Details
This function evaluates the provided effect synchronously, returning its
result directly. It is ideal for effects that do not fail or include
asynchronous operations. If the effect does fail or involves async tasks, it
will throw an error. Execution stops at the point of failure or asynchronous
operation, making it unsuitable for effects that require asynchronous
handling.
Important: Attempting to run effects that involve asynchronous operations
or failures will result in exceptions being thrown, so use this function with
care for purely synchronous and error-free effects.
When to Use
Use this function when:
You are sure that the effect will not fail or involve asynchronous
operations.
You need a direct, synchronous result from the effect.
You are working within a context where asynchronous effects are not
allowed.
Avoid using this function for effects that can fail or require asynchronous
handling. For such cases, consider using
runPromise
or
runSyncExit
.
@see ― runSyncExit for a version that returns an Exit type instead of
throwing an error.
@example
// Title: Synchronous Logging
import { Effect } from"effect"
constprogram= Effect.sync(() => {
console.log("Hello, World!")
return1
})
constresult= Effect.runSync(program)
// Output: Hello, World!
console.log(result)
// Output: 1
@example
// Title: Incorrect Usage with Failing or Async Effects
import { Effect } from "effect"
try {
// Attempt to run an effect that fails
Effect.runSync(Effect.fail("my error"))
} catch (e) {
console.error(e)
}
// Output:
// (FiberFailure) Error: my error
try {
// Attempt to run an effect that involves async work
Effect.runSync(Effect.promise(() => Promise.resolve(1)))
} catch (e) {
console.error(e)
}
// Output:
// (FiberFailure) AsyncFiberException: Fiber #0 cannot be resolved synchronously. This is caused by using runSync on an effect that performs async work
Performs the specified action for each element in an array.
@param ― callbackfn A function that accepts up to three arguments. forEach calls the callbackfn function one time for each element in the array.
@param ― thisArg An object to which the this keyword can refer in the callbackfn function. If thisArg is omitted, undefined is used as the this value.
forEach((
duration: Duration.Duration
duration,
i: number
i) => {
18
var console:Console
The console module provides a simple debugging console that is similar to the
JavaScript console mechanism provided by web browsers.
The module exports two specific components:
A Console class with methods such as console.log(), console.error() and console.warn() that can be used to write to any Node.js stream.
A global console instance configured to write to process.stdout and
process.stderr. The global console can be used without importing the node:console module.
Warning: The global console object's methods are neither consistently
synchronous like the browser APIs they resemble, nor are they consistently
asynchronous like all other Node.js streams. See the note on process I/O for
more information.
Example using the global console:
console.log('hello world');
// Prints: hello world, to stdout
console.log('hello %s', 'world');
// Prints: hello world, to stdout
console.error(newError('Whoops, something bad happened'));
// Prints error message and stack trace to stderr:
// Error: Whoops, something bad happened
// at [eval]:5:15
// at Script.runInThisContext (node:vm:132:18)
// at Object.runInThisContext (node:vm:309:38)
// at node:internal/process/execution:77:19
// at [eval]-wrapper:6:22
// at evalScript (node:internal/process/execution:76:60)
// at node:internal/main/eval_string:23:3
constname='Will Robinson';
console.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to stderr
Example using the Console class:
constout=getStreamSomehow();
consterr=getStreamSomehow();
constmyConsole=new console.Console(out, err);
myConsole.log('hello world');
// Prints: hello world, to out
myConsole.log('hello %s', 'world');
// Prints: hello world, to out
myConsole.error(newError('Whoops, something bad happened'));
// Prints: [Error: Whoops, something bad happened], to err
Prints to stdout with newline. Multiple arguments can be passed, with the
first used as the primary message and all additional used as substitution
values similar to printf(3)
(the arguments are all passed to util.format()).
A schedule that always recurs, but will wait a certain amount between
repetitions, given by base * factor.pow(n), where n is the number of
repetitions so far. Returns the current duration between recurrences.
The Schedule.union operator selects the shortest delay at each step, so when combining an exponential schedule with a spaced interval, the initial recurrences will follow the exponential backoff, then settle into the spaced interval once the delays exceed that value.
Intersection
Combines two schedules and recurs only if both schedules want to continue, using the longer delay.
Example (Limiting Exponential Backoff with a Fixed Number of Retries)
A Schedule<Out, In, R> defines a recurring schedule, which consumes
values of type In, and which returns values of type Out.
Schedules are defined as a possibly infinite set of intervals spread out over
time. Each interval defines a window in which recurrence is possible.
When schedules are used to repeat or retry effects, the starting boundary of
each interval produced by a schedule is used as the moment when the effect
will be executed again.
Schedules compose in the following primary ways:
Union: performs the union of the intervals of two schedules
Intersection: performs the intersection of the intervals of two schedules
Sequence: concatenates the intervals of one schedule onto another
In addition, schedule inputs and outputs can be transformed, filtered (to
terminate a schedule early in response to some input or output), and so
forth.
A variety of other operators exist for transforming and combining schedules,
and the companion object for Schedule contains all common types of
schedules, both for performing retrying, as well as performing repetition.
Converts a Chunk into an Array. If the provided Chunk is non-empty
(NonEmptyChunk), the function will return a NonEmptyArray, ensuring the
non-empty property is preserved.
Executes an effect synchronously, running it immediately and returning the
result.
Details
This function evaluates the provided effect synchronously, returning its
result directly. It is ideal for effects that do not fail or include
asynchronous operations. If the effect does fail or involves async tasks, it
will throw an error. Execution stops at the point of failure or asynchronous
operation, making it unsuitable for effects that require asynchronous
handling.
Important: Attempting to run effects that involve asynchronous operations
or failures will result in exceptions being thrown, so use this function with
care for purely synchronous and error-free effects.
When to Use
Use this function when:
You are sure that the effect will not fail or involve asynchronous
operations.
You need a direct, synchronous result from the effect.
You are working within a context where asynchronous effects are not
allowed.
Avoid using this function for effects that can fail or require asynchronous
handling. For such cases, consider using
runPromise
or
runSyncExit
.
@see ― runSyncExit for a version that returns an Exit type instead of
throwing an error.
@example
// Title: Synchronous Logging
import { Effect } from"effect"
constprogram= Effect.sync(() => {
console.log("Hello, World!")
return1
})
constresult= Effect.runSync(program)
// Output: Hello, World!
console.log(result)
// Output: 1
@example
// Title: Incorrect Usage with Failing or Async Effects
import { Effect } from "effect"
try {
// Attempt to run an effect that fails
Effect.runSync(Effect.fail("my error"))
} catch (e) {
console.error(e)
}
// Output:
// (FiberFailure) Error: my error
try {
// Attempt to run an effect that involves async work
Effect.runSync(Effect.promise(() => Promise.resolve(1)))
} catch (e) {
console.error(e)
}
// Output:
// (FiberFailure) AsyncFiberException: Fiber #0 cannot be resolved synchronously. This is caused by using runSync on an effect that performs async work
Performs the specified action for each element in an array.
@param ― callbackfn A function that accepts up to three arguments. forEach calls the callbackfn function one time for each element in the array.
@param ― thisArg An object to which the this keyword can refer in the callbackfn function. If thisArg is omitted, undefined is used as the this value.
forEach((
duration: Duration.Duration
duration,
i: number
i) => {
18
var console:Console
The console module provides a simple debugging console that is similar to the
JavaScript console mechanism provided by web browsers.
The module exports two specific components:
A Console class with methods such as console.log(), console.error() and console.warn() that can be used to write to any Node.js stream.
A global console instance configured to write to process.stdout and
process.stderr. The global console can be used without importing the node:console module.
Warning: The global console object's methods are neither consistently
synchronous like the browser APIs they resemble, nor are they consistently
asynchronous like all other Node.js streams. See the note on process I/O for
more information.
Example using the global console:
console.log('hello world');
// Prints: hello world, to stdout
console.log('hello %s', 'world');
// Prints: hello world, to stdout
console.error(newError('Whoops, something bad happened'));
// Prints error message and stack trace to stderr:
// Error: Whoops, something bad happened
// at [eval]:5:15
// at Script.runInThisContext (node:vm:132:18)
// at Object.runInThisContext (node:vm:309:38)
// at node:internal/process/execution:77:19
// at [eval]-wrapper:6:22
// at evalScript (node:internal/process/execution:76:60)
// at node:internal/main/eval_string:23:3
constname='Will Robinson';
console.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to stderr
Example using the Console class:
constout=getStreamSomehow();
consterr=getStreamSomehow();
constmyConsole=new console.Console(out, err);
myConsole.log('hello world');
// Prints: hello world, to out
myConsole.log('hello %s', 'world');
// Prints: hello world, to out
myConsole.error(newError('Whoops, something bad happened'));
// Prints: [Error: Whoops, something bad happened], to err
Prints to stdout with newline. Multiple arguments can be passed, with the
first used as the primary message and all additional used as substitution
values similar to printf(3)
(the arguments are all passed to util.format()).
A schedule that always recurs, but will wait a certain amount between
repetitions, given by base * factor.pow(n), where n is the number of
repetitions so far. Returns the current duration between recurrences.
The Schedule.intersect operator enforces both schedules’ constraints. In this example, the schedule follows an exponential backoff but stops after 5 recurrences due to the Schedule.recurs(5) limit.
Sequencing
Combines two schedules by running the first one fully, then switching to the second.
Example (Switching from Fixed Retries to Periodic Execution)
A Schedule<Out, In, R> defines a recurring schedule, which consumes
values of type In, and which returns values of type Out.
Schedules are defined as a possibly infinite set of intervals spread out over
time. Each interval defines a window in which recurrence is possible.
When schedules are used to repeat or retry effects, the starting boundary of
each interval produced by a schedule is used as the moment when the effect
will be executed again.
Schedules compose in the following primary ways:
Union: performs the union of the intervals of two schedules
Intersection: performs the intersection of the intervals of two schedules
Sequence: concatenates the intervals of one schedule onto another
In addition, schedule inputs and outputs can be transformed, filtered (to
terminate a schedule early in response to some input or output), and so
forth.
A variety of other operators exist for transforming and combining schedules,
and the companion object for Schedule contains all common types of
schedules, both for performing retrying, as well as performing repetition.
Converts a Chunk into an Array. If the provided Chunk is non-empty
(NonEmptyChunk), the function will return a NonEmptyArray, ensuring the
non-empty property is preserved.
Executes an effect synchronously, running it immediately and returning the
result.
Details
This function evaluates the provided effect synchronously, returning its
result directly. It is ideal for effects that do not fail or include
asynchronous operations. If the effect does fail or involves async tasks, it
will throw an error. Execution stops at the point of failure or asynchronous
operation, making it unsuitable for effects that require asynchronous
handling.
Important: Attempting to run effects that involve asynchronous operations
or failures will result in exceptions being thrown, so use this function with
care for purely synchronous and error-free effects.
When to Use
Use this function when:
You are sure that the effect will not fail or involve asynchronous
operations.
You need a direct, synchronous result from the effect.
You are working within a context where asynchronous effects are not
allowed.
Avoid using this function for effects that can fail or require asynchronous
handling. For such cases, consider using
runPromise
or
runSyncExit
.
@see ― runSyncExit for a version that returns an Exit type instead of
throwing an error.
@example
// Title: Synchronous Logging
import { Effect } from"effect"
constprogram= Effect.sync(() => {
console.log("Hello, World!")
return1
})
constresult= Effect.runSync(program)
// Output: Hello, World!
console.log(result)
// Output: 1
@example
// Title: Incorrect Usage with Failing or Async Effects
import { Effect } from "effect"
try {
// Attempt to run an effect that fails
Effect.runSync(Effect.fail("my error"))
} catch (e) {
console.error(e)
}
// Output:
// (FiberFailure) Error: my error
try {
// Attempt to run an effect that involves async work
Effect.runSync(Effect.promise(() => Promise.resolve(1)))
} catch (e) {
console.error(e)
}
// Output:
// (FiberFailure) AsyncFiberException: Fiber #0 cannot be resolved synchronously. This is caused by using runSync on an effect that performs async work
Performs the specified action for each element in an array.
@param ― callbackfn A function that accepts up to three arguments. forEach calls the callbackfn function one time for each element in the array.
@param ― thisArg An object to which the this keyword can refer in the callbackfn function. If thisArg is omitted, undefined is used as the this value.
forEach((
duration: Duration.Duration
duration,
i: number
i) => {
18
var console:Console
The console module provides a simple debugging console that is similar to the
JavaScript console mechanism provided by web browsers.
The module exports two specific components:
A Console class with methods such as console.log(), console.error() and console.warn() that can be used to write to any Node.js stream.
A global console instance configured to write to process.stdout and
process.stderr. The global console can be used without importing the node:console module.
Warning: The global console object's methods are neither consistently
synchronous like the browser APIs they resemble, nor are they consistently
asynchronous like all other Node.js streams. See the note on process I/O for
more information.
Example using the global console:
console.log('hello world');
// Prints: hello world, to stdout
console.log('hello %s', 'world');
// Prints: hello world, to stdout
console.error(newError('Whoops, something bad happened'));
// Prints error message and stack trace to stderr:
// Error: Whoops, something bad happened
// at [eval]:5:15
// at Script.runInThisContext (node:vm:132:18)
// at Object.runInThisContext (node:vm:309:38)
// at node:internal/process/execution:77:19
// at [eval]-wrapper:6:22
// at evalScript (node:internal/process/execution:76:60)
// at node:internal/main/eval_string:23:3
constname='Will Robinson';
console.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to stderr
Example using the Console class:
constout=getStreamSomehow();
consterr=getStreamSomehow();
constmyConsole=new console.Console(out, err);
myConsole.log('hello world');
// Prints: hello world, to out
myConsole.log('hello %s', 'world');
// Prints: hello world, to out
myConsole.error(newError('Whoops, something bad happened'));
// Prints: [Error: Whoops, something bad happened], to err
Prints to stdout with newline. Multiple arguments can be passed, with the
first used as the primary message and all additional used as substitution
values similar to printf(3)
(the arguments are all passed to util.format()).
The first schedule runs until completion, after which the second schedule takes over. In this example, the effect initially executes 5 times with no delay, then continues every 1 second.
Adding Randomness to Retry Delays
The Schedule.jittered combinator modifies a schedule by applying a random delay within a specified range.
When a resource is out of service due to overload or contention, retrying and backing off doesn’t help us. If all failed API calls are backed off to the same point of time, they cause another overload or contention. Jitter adds some amount of randomness to the delay of the schedule. This helps us to avoid ending up accidentally synchronizing and taking the service down by accident.
Research suggests that Schedule.jittered(0.0, 1.0) is an effective way to introduce randomness in retries.
A Schedule<Out, In, R> defines a recurring schedule, which consumes
values of type In, and which returns values of type Out.
Schedules are defined as a possibly infinite set of intervals spread out over
time. Each interval defines a window in which recurrence is possible.
When schedules are used to repeat or retry effects, the starting boundary of
each interval produced by a schedule is used as the moment when the effect
will be executed again.
Schedules compose in the following primary ways:
Union: performs the union of the intervals of two schedules
Intersection: performs the intersection of the intervals of two schedules
Sequence: concatenates the intervals of one schedule onto another
In addition, schedule inputs and outputs can be transformed, filtered (to
terminate a schedule early in response to some input or output), and so
forth.
A variety of other operators exist for transforming and combining schedules,
and the companion object for Schedule contains all common types of
schedules, both for performing retrying, as well as performing repetition.
Converts a Chunk into an Array. If the provided Chunk is non-empty
(NonEmptyChunk), the function will return a NonEmptyArray, ensuring the
non-empty property is preserved.
Executes an effect synchronously, running it immediately and returning the
result.
Details
This function evaluates the provided effect synchronously, returning its
result directly. It is ideal for effects that do not fail or include
asynchronous operations. If the effect does fail or involves async tasks, it
will throw an error. Execution stops at the point of failure or asynchronous
operation, making it unsuitable for effects that require asynchronous
handling.
Important: Attempting to run effects that involve asynchronous operations
or failures will result in exceptions being thrown, so use this function with
care for purely synchronous and error-free effects.
When to Use
Use this function when:
You are sure that the effect will not fail or involve asynchronous
operations.
You need a direct, synchronous result from the effect.
You are working within a context where asynchronous effects are not
allowed.
Avoid using this function for effects that can fail or require asynchronous
handling. For such cases, consider using
runPromise
or
runSyncExit
.
@see ― runSyncExit for a version that returns an Exit type instead of
throwing an error.
@example
// Title: Synchronous Logging
import { Effect } from"effect"
constprogram= Effect.sync(() => {
console.log("Hello, World!")
return1
})
constresult= Effect.runSync(program)
// Output: Hello, World!
console.log(result)
// Output: 1
@example
// Title: Incorrect Usage with Failing or Async Effects
import { Effect } from "effect"
try {
// Attempt to run an effect that fails
Effect.runSync(Effect.fail("my error"))
} catch (e) {
console.error(e)
}
// Output:
// (FiberFailure) Error: my error
try {
// Attempt to run an effect that involves async work
Effect.runSync(Effect.promise(() => Promise.resolve(1)))
} catch (e) {
console.error(e)
}
// Output:
// (FiberFailure) AsyncFiberException: Fiber #0 cannot be resolved synchronously. This is caused by using runSync on an effect that performs async work
Performs the specified action for each element in an array.
@param ― callbackfn A function that accepts up to three arguments. forEach calls the callbackfn function one time for each element in the array.
@param ― thisArg An object to which the this keyword can refer in the callbackfn function. If thisArg is omitted, undefined is used as the this value.
forEach((
duration: Duration.Duration
duration,
i: number
i) => {
18
var console:Console
The console module provides a simple debugging console that is similar to the
JavaScript console mechanism provided by web browsers.
The module exports two specific components:
A Console class with methods such as console.log(), console.error() and console.warn() that can be used to write to any Node.js stream.
A global console instance configured to write to process.stdout and
process.stderr. The global console can be used without importing the node:console module.
Warning: The global console object's methods are neither consistently
synchronous like the browser APIs they resemble, nor are they consistently
asynchronous like all other Node.js streams. See the note on process I/O for
more information.
Example using the global console:
console.log('hello world');
// Prints: hello world, to stdout
console.log('hello %s', 'world');
// Prints: hello world, to stdout
console.error(newError('Whoops, something bad happened'));
// Prints error message and stack trace to stderr:
// Error: Whoops, something bad happened
// at [eval]:5:15
// at Script.runInThisContext (node:vm:132:18)
// at Object.runInThisContext (node:vm:309:38)
// at node:internal/process/execution:77:19
// at [eval]-wrapper:6:22
// at evalScript (node:internal/process/execution:76:60)
// at node:internal/main/eval_string:23:3
constname='Will Robinson';
console.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to stderr
Example using the Console class:
constout=getStreamSomehow();
consterr=getStreamSomehow();
constmyConsole=new console.Console(out, err);
myConsole.log('hello world');
// Prints: hello world, to out
myConsole.log('hello %s', 'world');
// Prints: hello world, to out
myConsole.error(newError('Whoops, something bad happened'));
// Prints: [Error: Whoops, something bad happened], to err
Prints to stdout with newline. Multiple arguments can be passed, with the
first used as the primary message and all additional used as substitution
values similar to printf(3)
(the arguments are all passed to util.format()).
A schedule that always recurs, but will wait a certain amount between
repetitions, given by base * factor.pow(n), where n is the number of
repetitions so far. Returns the current duration between recurrences.
The Schedule.jittered combinator introduces randomness to delays within a range. For example, applying jitter to an exponential backoff ensures that each retry occurs at a slightly different time, reducing the risk of overwhelming the system.
Controlling Repetitions with Filters
You can use Schedule.whileInput or Schedule.whileOutput to limit how long a schedule continues based on conditions applied to its input or output.
A Schedule<Out, In, R> defines a recurring schedule, which consumes
values of type In, and which returns values of type Out.
Schedules are defined as a possibly infinite set of intervals spread out over
time. Each interval defines a window in which recurrence is possible.
When schedules are used to repeat or retry effects, the starting boundary of
each interval produced by a schedule is used as the moment when the effect
will be executed again.
Schedules compose in the following primary ways:
Union: performs the union of the intervals of two schedules
Intersection: performs the intersection of the intervals of two schedules
Sequence: concatenates the intervals of one schedule onto another
In addition, schedule inputs and outputs can be transformed, filtered (to
terminate a schedule early in response to some input or output), and so
forth.
A variety of other operators exist for transforming and combining schedules,
and the companion object for Schedule contains all common types of
schedules, both for performing retrying, as well as performing repetition.
Converts a Chunk into an Array. If the provided Chunk is non-empty
(NonEmptyChunk), the function will return a NonEmptyArray, ensuring the
non-empty property is preserved.
Executes an effect synchronously, running it immediately and returning the
result.
Details
This function evaluates the provided effect synchronously, returning its
result directly. It is ideal for effects that do not fail or include
asynchronous operations. If the effect does fail or involves async tasks, it
will throw an error. Execution stops at the point of failure or asynchronous
operation, making it unsuitable for effects that require asynchronous
handling.
Important: Attempting to run effects that involve asynchronous operations
or failures will result in exceptions being thrown, so use this function with
care for purely synchronous and error-free effects.
When to Use
Use this function when:
You are sure that the effect will not fail or involve asynchronous
operations.
You need a direct, synchronous result from the effect.
You are working within a context where asynchronous effects are not
allowed.
Avoid using this function for effects that can fail or require asynchronous
handling. For such cases, consider using
runPromise
or
runSyncExit
.
@see ― runSyncExit for a version that returns an Exit type instead of
throwing an error.
@example
// Title: Synchronous Logging
import { Effect } from"effect"
constprogram= Effect.sync(() => {
console.log("Hello, World!")
return1
})
constresult= Effect.runSync(program)
// Output: Hello, World!
console.log(result)
// Output: 1
@example
// Title: Incorrect Usage with Failing or Async Effects
import { Effect } from "effect"
try {
// Attempt to run an effect that fails
Effect.runSync(Effect.fail("my error"))
} catch (e) {
console.error(e)
}
// Output:
// (FiberFailure) Error: my error
try {
// Attempt to run an effect that involves async work
Effect.runSync(Effect.promise(() => Promise.resolve(1)))
} catch (e) {
console.error(e)
}
// Output:
// (FiberFailure) AsyncFiberException: Fiber #0 cannot be resolved synchronously. This is caused by using runSync on an effect that performs async work
Performs the specified action for each element in an array.
@param ― callbackfn A function that accepts up to three arguments. forEach calls the callbackfn function one time for each element in the array.
@param ― thisArg An object to which the this keyword can refer in the callbackfn function. If thisArg is omitted, undefined is used as the this value.
forEach((
duration: Duration.Duration
duration,
i: number
i) => {
18
var console:Console
The console module provides a simple debugging console that is similar to the
JavaScript console mechanism provided by web browsers.
The module exports two specific components:
A Console class with methods such as console.log(), console.error() and console.warn() that can be used to write to any Node.js stream.
A global console instance configured to write to process.stdout and
process.stderr. The global console can be used without importing the node:console module.
Warning: The global console object's methods are neither consistently
synchronous like the browser APIs they resemble, nor are they consistently
asynchronous like all other Node.js streams. See the note on process I/O for
more information.
Example using the global console:
console.log('hello world');
// Prints: hello world, to stdout
console.log('hello %s', 'world');
// Prints: hello world, to stdout
console.error(newError('Whoops, something bad happened'));
// Prints error message and stack trace to stderr:
// Error: Whoops, something bad happened
// at [eval]:5:15
// at Script.runInThisContext (node:vm:132:18)
// at Object.runInThisContext (node:vm:309:38)
// at node:internal/process/execution:77:19
// at [eval]-wrapper:6:22
// at evalScript (node:internal/process/execution:76:60)
// at node:internal/main/eval_string:23:3
constname='Will Robinson';
console.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to stderr
Example using the Console class:
constout=getStreamSomehow();
consterr=getStreamSomehow();
constmyConsole=new console.Console(out, err);
myConsole.log('hello world');
// Prints: hello world, to out
myConsole.log('hello %s', 'world');
// Prints: hello world, to out
myConsole.error(newError('Whoops, something bad happened'));
// Prints: [Error: Whoops, something bad happened], to err
Prints to stdout with newline. Multiple arguments can be passed, with the
first used as the primary message and all additional used as substitution
values similar to printf(3)
(the arguments are all passed to util.format()).
Schedule.whileOutput filters repetitions based on the output of the schedule. In this example, the schedule stops once the output exceeds 2, even though Schedule.recurs(5) allows up to 5 repetitions.
Adjusting Delays Based on Output
The Schedule.modifyDelay combinator allows you to dynamically change the delay of a schedule based on the number of repetitions or other output conditions.
Example (Reducing Delay After a Certain Number of Repetitions)
A Schedule<Out, In, R> defines a recurring schedule, which consumes
values of type In, and which returns values of type Out.
Schedules are defined as a possibly infinite set of intervals spread out over
time. Each interval defines a window in which recurrence is possible.
When schedules are used to repeat or retry effects, the starting boundary of
each interval produced by a schedule is used as the moment when the effect
will be executed again.
Schedules compose in the following primary ways:
Union: performs the union of the intervals of two schedules
Intersection: performs the intersection of the intervals of two schedules
Sequence: concatenates the intervals of one schedule onto another
In addition, schedule inputs and outputs can be transformed, filtered (to
terminate a schedule early in response to some input or output), and so
forth.
A variety of other operators exist for transforming and combining schedules,
and the companion object for Schedule contains all common types of
schedules, both for performing retrying, as well as performing repetition.
Converts a Chunk into an Array. If the provided Chunk is non-empty
(NonEmptyChunk), the function will return a NonEmptyArray, ensuring the
non-empty property is preserved.
Executes an effect synchronously, running it immediately and returning the
result.
Details
This function evaluates the provided effect synchronously, returning its
result directly. It is ideal for effects that do not fail or include
asynchronous operations. If the effect does fail or involves async tasks, it
will throw an error. Execution stops at the point of failure or asynchronous
operation, making it unsuitable for effects that require asynchronous
handling.
Important: Attempting to run effects that involve asynchronous operations
or failures will result in exceptions being thrown, so use this function with
care for purely synchronous and error-free effects.
When to Use
Use this function when:
You are sure that the effect will not fail or involve asynchronous
operations.
You need a direct, synchronous result from the effect.
You are working within a context where asynchronous effects are not
allowed.
Avoid using this function for effects that can fail or require asynchronous
handling. For such cases, consider using
runPromise
or
runSyncExit
.
@see ― runSyncExit for a version that returns an Exit type instead of
throwing an error.
@example
// Title: Synchronous Logging
import { Effect } from"effect"
constprogram= Effect.sync(() => {
console.log("Hello, World!")
return1
})
constresult= Effect.runSync(program)
// Output: Hello, World!
console.log(result)
// Output: 1
@example
// Title: Incorrect Usage with Failing or Async Effects
import { Effect } from "effect"
try {
// Attempt to run an effect that fails
Effect.runSync(Effect.fail("my error"))
} catch (e) {
console.error(e)
}
// Output:
// (FiberFailure) Error: my error
try {
// Attempt to run an effect that involves async work
Effect.runSync(Effect.promise(() => Promise.resolve(1)))
} catch (e) {
console.error(e)
}
// Output:
// (FiberFailure) AsyncFiberException: Fiber #0 cannot be resolved synchronously. This is caused by using runSync on an effect that performs async work
Performs the specified action for each element in an array.
@param ― callbackfn A function that accepts up to three arguments. forEach calls the callbackfn function one time for each element in the array.
@param ― thisArg An object to which the this keyword can refer in the callbackfn function. If thisArg is omitted, undefined is used as the this value.
forEach((
duration: Duration.Duration
duration,
i: number
i) => {
18
var console:Console
The console module provides a simple debugging console that is similar to the
JavaScript console mechanism provided by web browsers.
The module exports two specific components:
A Console class with methods such as console.log(), console.error() and console.warn() that can be used to write to any Node.js stream.
A global console instance configured to write to process.stdout and
process.stderr. The global console can be used without importing the node:console module.
Warning: The global console object's methods are neither consistently
synchronous like the browser APIs they resemble, nor are they consistently
asynchronous like all other Node.js streams. See the note on process I/O for
more information.
Example using the global console:
console.log('hello world');
// Prints: hello world, to stdout
console.log('hello %s', 'world');
// Prints: hello world, to stdout
console.error(newError('Whoops, something bad happened'));
// Prints error message and stack trace to stderr:
// Error: Whoops, something bad happened
// at [eval]:5:15
// at Script.runInThisContext (node:vm:132:18)
// at Object.runInThisContext (node:vm:309:38)
// at node:internal/process/execution:77:19
// at [eval]-wrapper:6:22
// at evalScript (node:internal/process/execution:76:60)
// at node:internal/main/eval_string:23:3
constname='Will Robinson';
console.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to stderr
Example using the Console class:
constout=getStreamSomehow();
consterr=getStreamSomehow();
constmyConsole=new console.Console(out, err);
myConsole.log('hello world');
// Prints: hello world, to out
myConsole.log('hello %s', 'world');
// Prints: hello world, to out
myConsole.error(newError('Whoops, something bad happened'));
// Prints: [Error: Whoops, something bad happened], to err
Prints to stdout with newline. Multiple arguments can be passed, with the
first used as the primary message and all additional used as substitution
values similar to printf(3)
(the arguments are all passed to util.format()).
The delay modification applies dynamically during execution. In this example, the first three repetitions follow the original 1-second spacing. After that, the delay drops to 100 milliseconds, making subsequent repetitions occur more frequently.
Tapping
Schedule.tapInput and Schedule.tapOutput allow you to perform additional effectful operations on a schedule’s input or output without modifying its behavior.
A Schedule<Out, In, R> defines a recurring schedule, which consumes
values of type In, and which returns values of type Out.
Schedules are defined as a possibly infinite set of intervals spread out over
time. Each interval defines a window in which recurrence is possible.
When schedules are used to repeat or retry effects, the starting boundary of
each interval produced by a schedule is used as the moment when the effect
will be executed again.
Schedules compose in the following primary ways:
Union: performs the union of the intervals of two schedules
Intersection: performs the intersection of the intervals of two schedules
Sequence: concatenates the intervals of one schedule onto another
In addition, schedule inputs and outputs can be transformed, filtered (to
terminate a schedule early in response to some input or output), and so
forth.
A variety of other operators exist for transforming and combining schedules,
and the companion object for Schedule contains all common types of
schedules, both for performing retrying, as well as performing repetition.
Converts a Chunk into an Array. If the provided Chunk is non-empty
(NonEmptyChunk), the function will return a NonEmptyArray, ensuring the
non-empty property is preserved.
Executes an effect synchronously, running it immediately and returning the
result.
Details
This function evaluates the provided effect synchronously, returning its
result directly. It is ideal for effects that do not fail or include
asynchronous operations. If the effect does fail or involves async tasks, it
will throw an error. Execution stops at the point of failure or asynchronous
operation, making it unsuitable for effects that require asynchronous
handling.
Important: Attempting to run effects that involve asynchronous operations
or failures will result in exceptions being thrown, so use this function with
care for purely synchronous and error-free effects.
When to Use
Use this function when:
You are sure that the effect will not fail or involve asynchronous
operations.
You need a direct, synchronous result from the effect.
You are working within a context where asynchronous effects are not
allowed.
Avoid using this function for effects that can fail or require asynchronous
handling. For such cases, consider using
runPromise
or
runSyncExit
.
@see ― runSyncExit for a version that returns an Exit type instead of
throwing an error.
@example
// Title: Synchronous Logging
import { Effect } from"effect"
constprogram= Effect.sync(() => {
console.log("Hello, World!")
return1
})
constresult= Effect.runSync(program)
// Output: Hello, World!
console.log(result)
// Output: 1
@example
// Title: Incorrect Usage with Failing or Async Effects
import { Effect } from "effect"
try {
// Attempt to run an effect that fails
Effect.runSync(Effect.fail("my error"))
} catch (e) {
console.error(e)
}
// Output:
// (FiberFailure) Error: my error
try {
// Attempt to run an effect that involves async work
Effect.runSync(Effect.promise(() => Promise.resolve(1)))
} catch (e) {
console.error(e)
}
// Output:
// (FiberFailure) AsyncFiberException: Fiber #0 cannot be resolved synchronously. This is caused by using runSync on an effect that performs async work
Performs the specified action for each element in an array.
@param ― callbackfn A function that accepts up to three arguments. forEach calls the callbackfn function one time for each element in the array.
@param ― thisArg An object to which the this keyword can refer in the callbackfn function. If thisArg is omitted, undefined is used as the this value.
forEach((
duration: Duration.Duration
duration,
i: number
i) => {
18
var console:Console
The console module provides a simple debugging console that is similar to the
JavaScript console mechanism provided by web browsers.
The module exports two specific components:
A Console class with methods such as console.log(), console.error() and console.warn() that can be used to write to any Node.js stream.
A global console instance configured to write to process.stdout and
process.stderr. The global console can be used without importing the node:console module.
Warning: The global console object's methods are neither consistently
synchronous like the browser APIs they resemble, nor are they consistently
asynchronous like all other Node.js streams. See the note on process I/O for
more information.
Example using the global console:
console.log('hello world');
// Prints: hello world, to stdout
console.log('hello %s', 'world');
// Prints: hello world, to stdout
console.error(newError('Whoops, something bad happened'));
// Prints error message and stack trace to stderr:
// Error: Whoops, something bad happened
// at [eval]:5:15
// at Script.runInThisContext (node:vm:132:18)
// at Object.runInThisContext (node:vm:309:38)
// at node:internal/process/execution:77:19
// at [eval]-wrapper:6:22
// at evalScript (node:internal/process/execution:76:60)
// at node:internal/main/eval_string:23:3
constname='Will Robinson';
console.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to stderr
Example using the Console class:
constout=getStreamSomehow();
consterr=getStreamSomehow();
constmyConsole=new console.Console(out, err);
myConsole.log('hello world');
// Prints: hello world, to out
myConsole.log('hello %s', 'world');
// Prints: hello world, to out
myConsole.error(newError('Whoops, something bad happened'));
// Prints: [Error: Whoops, something bad happened], to err
Prints to stdout with newline. Multiple arguments can be passed, with the
first used as the primary message and all additional used as substitution
values similar to printf(3)
(the arguments are all passed to util.format()).
Schedule.tapOutput runs an effect before each recurrence, using the schedule’s current output as input. This can be useful for logging, debugging, or triggering side effects.