Queue

@webda/core • Readme | API

Class: `abstract` Queue<T, K>

AbstractQueue implements the worker system

A Consumer allows you to define how to process message from the queue, implementing the retries policy

Extends

PubSubService<T, K>

Type parameters

• T = any

• K extends QueueParameters = QueueParameters

Constructors

new Queue(webda, name, params)

new Queue<T, K>(webda, name, params): Queue<T, K>

Service

Parameters

• webda: Core<CoreEvents>

The main instance of Webda

• name: string

The name of the service

• params: DeepPartial<K>= {}

The parameters block define in the configuration file

Returns

Queue<T, K>

Inherited from

PubSubService.constructor

Source

packages/core/src/services/service.ts:334

Properties

_createException

_createException: string

Inherited from

PubSubService._createException

Source

packages/core/src/services/service.ts:315

_initException

_initException: any = undefined

Inherited from

PubSubService._initException

Source

packages/core/src/services/service.ts:317

_initTime

_initTime: number

Inherited from

PubSubService._initTime

Source

packages/core/src/services/service.ts:316

_name

protected _name: string

Service name

Inherited from

PubSubService._name

Source

packages/core/src/services/service.ts:308

_timeout

protected _timeout: Timeout

Current timeout handler

Source

packages/core/src/queues/queueservice.ts:69

_webda

protected _webda: Core<CoreEvents>

Webda Core object

Inherited from

PubSubService._webda

Source

packages/core/src/services/service.ts:304

delayer

protected delayer: WaitDelayer

Delayer

Source

packages/core/src/queues/queueservice.ts:81

eventPrototype

eventPrototype: () => T

Returns

T

Source

packages/core/src/queues/queueservice.ts:82

failedIterations

protected failedIterations: number

Current pause instance

Source

packages/core/src/queues/queueservice.ts:77

logger

protected logger: Logger

Logger with class context

Inherited from

PubSubService.logger

Source

packages/core/src/services/service.ts:321

metrics

protected metrics: Object

Type declaration

errors

errors: Counter<string>

messages_pending

messages_pending: Gauge<string>

messages_received

messages_received: Counter<string>

messages_sent

messages_sent: Counter<string>

processing_duration

processing_duration: Histogram<string>

Inherited from

PubSubService.metrics

Source

packages/core/src/queues/pubsubservice.ts:12

parameters

protected parameters: K

Hold the parameters for your service

It will be bring from the webda.config.json

Inherited from

PubSubService.parameters

Source

packages/core/src/services/service.ts:314

captureRejectionSymbol

static readonly captureRejectionSymbol: typeof captureRejectionSymbol

Inherited from

PubSubService.captureRejectionSymbol

Source

packages/core/node_modules/@types/node/events.d.ts:328

captureRejections

static captureRejections: boolean

Sets or gets the default captureRejection value for all emitters.

Inherited from

PubSubService.captureRejections

Source

packages/core/node_modules/@types/node/events.d.ts:333

defaultMaxListeners

static defaultMaxListeners: number

Inherited from

PubSubService.defaultMaxListeners

Source

packages/core/node_modules/@types/node/events.d.ts:334

errorMonitor

static readonly errorMonitor: typeof errorMonitor

This symbol shall be used to install a listener for only monitoring 'error' events. Listeners installed using this symbol are called before the regular 'error' listeners are called.

Installing a listener using this symbol does not change the behavior once an 'error' event is emitted, therefore the process will still crash if no regular 'error' listener is installed.

Inherited from

PubSubService.errorMonitor

Source

packages/core/node_modules/@types/node/events.d.ts:327

Methods

__clean()

__clean(): Promise<void>

Clean the service data, can only be used in test mode

Returns

Promise<void>

Inherited from

PubSubService.__clean

Abstract

Source

packages/core/src/services/service.ts:642

addListener()

addListener(eventName, listener): this

Alias for emitter.on(eventName, listener).

Parameters

• eventName: string | symbol

• listener: (...args) => void

Returns

this

Inherited from

PubSubService.addListener

Since

v0.1.26

Source

packages/core/node_modules/@types/node/events.d.ts:354

addRoute()

protected addRoute(url, methods, executer, openapi, override): void

Add a route dynamicaly

Parameters

• url: string

of the route can contains dynamic part like {uuid}

• methods: HttpMethodType[]

• executer: Function

Method to execute for this route

• openapi: OpenAPIWebdaDefinition= {}

• override: boolean= false

Returns

void

Inherited from

PubSubService.addRoute

Source

packages/core/src/services/service.ts:482

authorizeClientEvent()

authorizeClientEvent(_event, _context): boolean

Authorize a public event subscription

Parameters

• _event: string

• _context: OperationContext<any, any>

Returns

boolean

Inherited from

PubSubService.authorizeClientEvent

Source

packages/core/src/services/service.ts:438

computeParameters()

computeParameters(): void

Used to compute or derivate input parameter to attribute

Returns

void

Inherited from

PubSubService.computeParameters

Source

packages/core/src/services/service.ts:352

consume()

consume(callback, eventPrototype?): CancelablePromise<void>

Work a queue calling the callback with every Event received If the callback is called without exception the deleteMessage is called

Parameters

• callback: (event) => Promise<void>

• eventPrototype?: () => T

consumerReceiveMessage()

protected consumerReceiveMessage(): Promise<Object>

Receive and process message from the queue

Returns

Promise<Object>

items

items: number

speed

speed: number

Source

packages/core/src/queues/queueservice.ts:109

deleteMessage()

abstract deleteMessage(id): Promise<void>

Delete one message based on its receipt

Parameters

• id: string

Returns

Promise<void>

Source

packages/core/src/queues/queueservice.ts:93

emit()

emit<Key>(event, data): boolean

Override to allow capturing long listeners

Type parameters

• Key extends string | number

Parameters

• event: symbol | Key

• data: Events[Key]

Returns

boolean

Inherited from

PubSubService.emit

Source

packages/core/src/services/service.ts:596

emitSync()

emitSync<Key>(event, data): Promise<any[]>

Emit the event with data and wait for Promise to finish if listener returned a Promise

Type parameters

• Key extends string | number

Parameters

• event: Key

• data: Events[Key]

Returns

Promise<any[]>

Inherited from

PubSubService.emitSync

Source

packages/core/src/services/service.ts:588

eventNames()

eventNames(): (string | symbol)[]

Returns an array listing the events for which the emitter has registered listeners. The values in the array are strings or Symbols.

const EventEmitter = require('events');
const myEE = new EventEmitter();
myEE.on('foo', () => {});
myEE.on('bar', () => {});

const sym = Symbol('symbol');
myEE.on(sym, () => {});

console.log(myEE.eventNames());
// Prints: [ 'foo', 'bar', Symbol(symbol) ]

Returns

(string | symbol)[]

Inherited from

PubSubService.eventNames

Since

v6.0.0

Source

packages/core/node_modules/@types/node/events.d.ts:669

getClientEvents()

getClientEvents(): string[]

Return the events that an external system can subscribe to

Returns

string[]

Inherited from

PubSubService.getClientEvents

Source

packages/core/src/services/service.ts:429

getMaxConsumers()

getMaxConsumers(): number

Return the max consumers for the queue

It is overridable so if a queue can retrieve several message at once it can just use the worker // and several messages at once

SQS for example will return this.parameters.maxConsumers / 10

Returns

number

Source

packages/core/src/queues/queueservice.ts:162

getMaxListeners()

getMaxListeners(): number

Returns the current max listener value for the EventEmitter which is either set by emitter.setMaxListeners(n) or defaults to defaultMaxListeners.

Returns

number

Inherited from

PubSubService.getMaxListeners

Since

v1.0.0

Source

packages/core/node_modules/@types/node/events.d.ts:526

getMetric()

getMetric<T>(type, configuration): T

Add service name label

Type parameters

• T = Counter<string> | Histogram<string> | Gauge<string>

Parameters

• type: Constructor<T, [MetricConfiguration<T>]>

• configuration: MetricConfiguration<T>

Returns

T

Inherited from

PubSubService.getMetric

Source

packages/core/src/services/service.ts:414

getName()

getName(): string

Get service name

Returns

string

Inherited from

PubSubService.getName

Source

packages/core/src/services/service.ts:633

getOpenApiReplacements()

getOpenApiReplacements(): any

Return variables for replacement in openapi

Returns

any

Inherited from

PubSubService.getOpenApiReplacements

Source

packages/core/src/services/service.ts:507

getOperationId()

getOperationId(id): string

If undefined is returned it cancel the operation registration

Parameters

• id: string

Returns

string

Inherited from

PubSubService.getOperationId

Source

packages/core/src/services/service.ts:471

getParameters()

getParameters(): K

Get the service parameters

Returns

K

Inherited from

PubSubService.getParameters

Source

packages/core/src/services/service.ts:359

getService()

getService<K>(service): K

Return a webda service

Type parameters

• K extends Service<ServiceParameters, Events>

Parameters

• service: string

name to retrieve

Returns

K

Inherited from

PubSubService.getService

Source

packages/core/src/services/service.ts:626

getUrl()

getUrl(url, _methods): string

Return the full path url based on parameters

Parameters

• url: string

relative url to service

• _methods: HttpMethodType[]

in case we need filtering (like Store)

Returns

string

absolute url or undefined if need to skip the Route

Inherited from

PubSubService.getUrl

Source

packages/core/src/services/service.ts:449

getWebda()

getWebda(): Core<CoreEvents>

Return WebdaCore

Returns

Core<CoreEvents>

Inherited from

PubSubService.getWebda

Source

packages/core/src/services/service.ts:366

init()

init(): Promise<Queue<T, K>>

Will be called after all the Services are created

Returns

Promise<Queue<T, K>>

Inherited from

PubSubService.init

Abstract

Source

packages/core/src/services/service.ts:570

initMetrics()

initMetrics(): void

Returns

void

Inherited from

PubSubService.initMetrics

Source

packages/core/src/queues/pubsubservice.ts:22

initOperations()

initOperations(): void

Init the operations

Returns

void

Inherited from

PubSubService.initOperations

Source

packages/core/src/services/service.ts:528

initRoutes()

initRoutes(): void

Init the routes

Returns

void

Inherited from

PubSubService.initRoutes

Source

packages/core/src/services/service.ts:514

listenerCount()

listenerCount(eventName): number

Returns the number of listeners listening to the event named eventName.

Parameters

• eventName: string | symbol

The name of the event being listened for

Returns

number

Inherited from

PubSubService.listenerCount

Since

v3.2.0

Source

packages/core/node_modules/@types/node/events.d.ts:616

listeners()

listeners(eventName): Function[]

Returns a copy of the array of listeners for the event named eventName.

server.on('connection', (stream) => {
  console.log('someone connected!');
});
console.log(util.inspect(server.listeners('connection')));
// Prints: [ [Function] ]

Parameters

• eventName: string | symbol

Returns

Function[]

Inherited from

PubSubService.listeners

Since

v0.1.26

Source

packages/core/node_modules/@types/node/events.d.ts:539

loadParameters()

loadParameters(params): ServiceParameters

Load the parameters for a service

Parameters

• params: DeepPartial<K>

Returns

ServiceParameters

Inherited from

PubSubService.loadParameters

Source

packages/core/src/services/service.ts:345

log()

log(level, ...args): void

Parameters

• level: WorkerLogLevel

to log

• ...args: any[]

Returns

void

Inherited from

PubSubService.log

Source

packages/core/src/services/service.ts:662

off()

off(eventName, listener): this

Alias for emitter.removeListener().

Parameters

• eventName: string | symbol

• listener: (...args) => void

Returns

this

Inherited from

PubSubService.off

Since

v10.0.0

Source

packages/core/node_modules/@types/node/events.d.ts:499

on()

on<Key>(event, listener): this

Type the listener part

Type parameters

• Key extends string | number

Parameters

• event: symbol | Key

• listener: (evt) => void

Returns

this

Inherited from

PubSubService.on

Source

packages/core/src/services/service.ts:607

onAsync()

onAsync<Key>(event, listener, queue): void

Listen to an event as on(...) would do except that it will be asynchronous

Type parameters

• Key extends string | number

Parameters

• event: Key

• listener: (evt) => void

• queue: string= undefined

Name of queue to use, can be undefined, queue name are used to define differents priorities

Returns

void

Inherited from

PubSubService.onAsync

Source

packages/core/src/services/service.ts:618

once()

once(eventName, listener): this

Adds a one-timelistener function for the event named eventName. The next time eventName is triggered, this listener is removed and then invoked.

server.once('connection', (stream) => {
  console.log('Ah, we have our first user!');
});

Returns a reference to the EventEmitter, so that calls can be chained.

By default, event listeners are invoked in the order they are added. Theemitter.prependOnceListener() method can be used as an alternative to add the event listener to the beginning of the listeners array.

const myEE = new EventEmitter();
myEE.once('foo', () => console.log('a'));
myEE.prependOnceListener('foo', () => console.log('b'));
myEE.emit('foo');
// Prints:
//   b
//   a

Parameters

• eventName: string | symbol

The name of the event.

• listener: (...args) => void

The callback function

Returns

this

Inherited from

PubSubService.once

Since

v0.3.0

Source

packages/core/node_modules/@types/node/events.d.ts:414

prependListener()

prependListener(eventName, listener): this

Adds the listener function to the beginning of the listeners array for the event named eventName. No checks are made to see if the listener has already been added. Multiple calls passing the same combination of eventNameand listener will result in the listener being added, and called, multiple times.

server.prependListener('connection', (stream) => {
  console.log('someone connected!');
});

Returns a reference to the EventEmitter, so that calls can be chained.

Parameters

• eventName: string | symbol

The name of the event.

• listener: (...args) => void

The callback function

Returns

this

Inherited from

PubSubService.prependListener

Since

v6.0.0

Source

packages/core/node_modules/@types/node/events.d.ts:634

prependOnceListener()

prependOnceListener(eventName, listener): this

Adds a one-timelistener function for the event named eventName to the beginning of the listeners array. The next time eventName is triggered, this listener is removed, and then invoked.

server.prependOnceListener('connection', (stream) => {
  console.log('Ah, we have our first user!');
});

Returns a reference to the EventEmitter, so that calls can be chained.

Parameters

• eventName: string | symbol

The name of the event.

• listener: (...args) => void

The callback function

Returns

this

Inherited from

PubSubService.prependOnceListener

Since

v6.0.0

Source

packages/core/node_modules/@types/node/events.d.ts:650

rawListeners()

rawListeners(eventName): Function[]

Returns a copy of the array of listeners for the event named eventName, including any wrappers (such as those created by .once()).

const emitter = new EventEmitter();
emitter.once('log', () => console.log('log once'));

// Returns a new Array with a function `onceWrapper` which has a property
// `listener` which contains the original listener bound above
const listeners = emitter.rawListeners('log');
const logFnWrapper = listeners[0];

// Logs "log once" to the console and does not unbind the `once` event
logFnWrapper.listener();

// Logs "log once" to the console and removes the listener
logFnWrapper();

emitter.on('log', () => console.log('log persistently'));
// Will return a new Array with a single function bound by `.on()` above
const newListeners = emitter.rawListeners('log');

// Logs "log persistently" twice
newListeners[0]();
emitter.emit('log');

Parameters

• eventName: string | symbol

Returns

Function[]

Inherited from

PubSubService.rawListeners

Since

v9.4.0

Source

packages/core/node_modules/@types/node/events.d.ts:569

receiveMessage()

abstract receiveMessage<L>(proto?): Promise<MessageReceipt<L>[]>

Receive one or several messages

Type parameters

• L

Parameters

• proto?: () => L

Returns

Promise<MessageReceipt<L>[]>

Source

packages/core/src/queues/queueservice.ts:87

reinit()

reinit(config): Promise<Queue<T, K>>

Parameters

• config: DeepPartial<K>

new parameters for the service

Returns

Promise<Queue<T, K>>

Inherited from

PubSubService.reinit

Source

packages/core/src/services/service.ts:579

removeAllListeners()

removeAllListeners(event?): this

Removes all listeners, or those of the specified eventName.

It is bad practice to remove listeners added elsewhere in the code, particularly when the EventEmitter instance was created by some other component or module (e.g. sockets or file streams).

Returns a reference to the EventEmitter, so that calls can be chained.

Parameters

• event?: string | symbol

Returns

this

Inherited from

PubSubService.removeAllListeners

Since

v0.1.26

Source

packages/core/node_modules/@types/node/events.d.ts:510

removeListener()

removeListener(eventName, listener): this

Removes the specified listener from the listener array for the event namedeventName.

const callback = (stream) => {
  console.log('someone connected!');
};
server.on('connection', callback);
// ...
server.removeListener('connection', callback);

removeListener() will remove, at most, one instance of a listener from the listener array. If any single listener has been added multiple times to the listener array for the specified eventName, then removeListener() must be called multiple times to remove each instance.

Once an event is emitted, all listeners attached to it at the time of emitting are called in order. This implies that anyremoveListener() or removeAllListeners() calls after emitting and before the last listener finishes execution will not remove them fromemit() in progress. Subsequent events behave as expected.

const myEmitter = new MyEmitter();

const callbackA = () => {
  console.log('A');
  myEmitter.removeListener('event', callbackB);
};

const callbackB = () => {
  console.log('B');
};

myEmitter.on('event', callbackA);

myEmitter.on('event', callbackB);

// callbackA removes listener callbackB but it will still be called.
// Internal listener array at time of emit [callbackA, callbackB]
myEmitter.emit('event');
// Prints:
//   A
//   B

// callbackB is now removed.
// Internal listener array [callbackA]
myEmitter.emit('event');
// Prints:
//   A

Because listeners are managed using an internal array, calling this will change the position indices of any listener registered after the listener being removed. This will not impact the order in which listeners are called, but it means that any copies of the listener array as returned by the emitter.listeners() method will need to be recreated.

When a single function has been added as a handler multiple times for a single event (as in the example below), removeListener() will remove the most recently added instance. In the example the once('ping')listener is removed:

const ee = new EventEmitter();

function pong() {
  console.log('pong');
}

ee.on('ping', pong);
ee.once('ping', pong);
ee.removeListener('ping', pong);

ee.emit('ping');
ee.emit('ping');

Returns a reference to the EventEmitter, so that calls can be chained.

Parameters

• eventName: string | symbol

• listener: (...args) => void

Returns

this

Inherited from

PubSubService.removeListener

Since

v0.1.26

Source

packages/core/node_modules/@types/node/events.d.ts:494

resolve()

resolve(): this

Create the delayer

Returns

this

Overrides

PubSubService.resolve

Source

packages/core/src/queues/queueservice.ts:98

sendMessage()

abstract sendMessage(event): Promise<void>

Send an event to the queue

Parameters

• event: T

Returns

Promise<void>

Inherited from

PubSubService.sendMessage

Source

packages/core/src/queues/pubsubservice.ts:49

setMaxListeners()

setMaxListeners(n): this

By default EventEmitters will print a warning if more than 10 listeners are added for a particular event. This is a useful default that helps finding memory leaks. The emitter.setMaxListeners() method allows the limit to be modified for this specific EventEmitter instance. The value can be set toInfinity (or 0) to indicate an unlimited number of listeners.

Returns a reference to the EventEmitter, so that calls can be chained.

Parameters

• n: number

Returns

this

Inherited from

PubSubService.setMaxListeners

Since

v0.3.5

Source

packages/core/node_modules/@types/node/events.d.ts:520

size()

abstract size(): Promise<number>

Size of the consumer if any

Returns

Promise<number>

Inherited from

PubSubService.size

Source

packages/core/src/queues/pubsubservice.ts:68

stop()

stop(): Promise<void>

Shutdown the current service if action need to be taken

Returns

Promise<void>

Inherited from

PubSubService.stop

Source

packages/core/src/services/service.ts:373

toJSON()

toJSON(): string

Prevent service to be serialized

Returns

string

Inherited from

PubSubService.toJSON

Source

packages/core/src/services/service.ts:560

toPublicJSON()

toPublicJSON(object): string

Convert an object to JSON using the Webda json filter

Service

Parameters

• object: unknown

The object to export

Returns

string

The export of the strip object ( removed all attribute with _ )

Inherited from

PubSubService.toPublicJSON

Source

packages/core/src/services/service.ts:552

toString()

toString(): string

Return service representation

Returns

string

Inherited from

PubSubService.toString

Source

packages/core/src/services/service.ts:380

unserialize()

unserialize<L>(data, proto?): L

Unserialize into class

Type parameters

• L

Parameters

• data: string

• proto?: () => L

Returns

L

Inherited from

PubSubService.unserialize

Source

packages/core/src/queues/pubsubservice.ts:57

getEventListeners()

static getEventListeners(emitter, name): Function[]

Returns a copy of the array of listeners for the event named eventName.

For EventEmitters this behaves exactly the same as calling .listeners on the emitter.

For EventTargets this is the only way to get the event listeners for the event target. This is useful for debugging and diagnostic purposes.

const { getEventListeners, EventEmitter } = require('events');

{
  const ee = new EventEmitter();
  const listener = () => console.log('Events are fun');
  ee.on('foo', listener);
  getEventListeners(ee, 'foo'); // [listener]
}
{
  const et = new EventTarget();
  const listener = () => console.log('Events are fun');
  et.addEventListener('foo', listener);
  getEventListeners(et, 'foo'); // [listener]
}

Parameters

• emitter: EventEmitter | _DOMEventTarget

• name: string | symbol

Returns

Function[]

Inherited from

PubSubService.getEventListeners

Since

v15.2.0, v14.17.0

Source

packages/core/node_modules/@types/node/events.d.ts:299

listenerCount()

static listenerCount(emitter, eventName): number

A class method that returns the number of listeners for the given eventNameregistered on the given emitter.

const { EventEmitter, listenerCount } = require('events');
const myEmitter = new EventEmitter();
myEmitter.on('event', () => {});
myEmitter.on('event', () => {});
console.log(listenerCount(myEmitter, 'event'));
// Prints: 2

Parameters

• emitter: EventEmitter

The emitter to query

• eventName: string | symbol

The event name

Returns

number

Inherited from

PubSubService.listenerCount

Since

v0.9.12

Deprecated

Since v3.2.0 - Use listenerCount instead.

Source

packages/core/node_modules/@types/node/events.d.ts:271

on()

static on(emitter, eventName, options?): AsyncIterableIterator<any, any, any>

const { on, EventEmitter } = require('events');

(async () => {
  const ee = new EventEmitter();

  // Emit later on
  process.nextTick(() => {
    ee.emit('foo', 'bar');
    ee.emit('foo', 42);
  });

  for await (const event of on(ee, 'foo')) {
    // The execution of this inner block is synchronous and it
    // processes one event at a time (even with await). Do not use
    // if concurrent execution is required.
    console.log(event); // prints ['bar'] [42]
  }
  // Unreachable here
})();

Returns an AsyncIterator that iterates eventName events. It will throw if the EventEmitter emits 'error'. It removes all listeners when exiting the loop. The value returned by each iteration is an array composed of the emitted event arguments.

An AbortSignal can be used to cancel waiting on events:

const { on, EventEmitter } = require('events');
const ac = new AbortController();

(async () => {
  const ee = new EventEmitter();

  // Emit later on
  process.nextTick(() => {
    ee.emit('foo', 'bar');
    ee.emit('foo', 42);
  });

  for await (const event of on(ee, 'foo', { signal: ac.signal })) {
    // The execution of this inner block is synchronous and it
    // processes one event at a time (even with await). Do not use
    // if concurrent execution is required.
    console.log(event); // prints ['bar'] [42]
  }
  // Unreachable here
})();

process.nextTick(() => ac.abort());

Parameters

• emitter: EventEmitter

• eventName: string

The name of the event being listened for

• options?: StaticEventEmitterOptions

Returns

AsyncIterableIterator<any, any, any>

that iterates eventName events emitted by the emitter

Inherited from

PubSubService.on

Since

v13.6.0, v12.16.0

Source

packages/core/node_modules/@types/node/events.d.ts:254

once()

once(emitter, eventName, options)

static once(emitter, eventName, options?): Promise<any[]>

Creates a Promise that is fulfilled when the EventEmitter emits the given event or that is rejected if the EventEmitter emits 'error' while waiting. The Promise will resolve with an array of all the arguments emitted to the given event.

This method is intentionally generic and works with the web platform EventTarget interface, which has no special'error' event semantics and does not listen to the 'error' event.

const { once, EventEmitter } = require('events');

async function run() {
  const ee = new EventEmitter();

  process.nextTick(() => {
    ee.emit('myevent', 42);
  });

  const [value] = await once(ee, 'myevent');
  console.log(value);

  const err = new Error('kaboom');
  process.nextTick(() => {
    ee.emit('error', err);
  });

  try {
    await once(ee, 'myevent');
  } catch (err) {
    console.log('error happened', err);
  }
}

run();

The special handling of the 'error' event is only used when events.once()is used to wait for another event. If events.once() is used to wait for the 'error' event itself, then it is treated as any other kind of event without special handling:

const { EventEmitter, once } = require('events');

const ee = new EventEmitter();

once(ee, 'error')
  .then(([err]) => console.log('ok', err.message))
  .catch((err) => console.log('error', err.message));

ee.emit('error', new Error('boom'));

// Prints: ok boom

An AbortSignal can be used to cancel waiting for the event:

const { EventEmitter, once } = require('events');

const ee = new EventEmitter();
const ac = new AbortController();

async function foo(emitter, event, signal) {
  try {
    await once(emitter, event, { signal });
    console.log('event emitted!');
  } catch (error) {
    if (error.name === 'AbortError') {
      console.error('Waiting for the event was canceled!');
    } else {
      console.error('There was an error', error.message);
    }
  }
}

foo(ee, 'foo', ac.signal);
ac.abort(); // Abort waiting for the event
ee.emit('foo'); // Prints: Waiting for the event was canceled!

Parameters

• emitter: _NodeEventTarget

• eventName: string | symbol

• options?: StaticEventEmitterOptions

Returns

Promise<any[]>

Inherited from

PubSubService.once

Since

v11.13.0, v10.16.0

Source

packages/core/node_modules/@types/node/events.d.ts:194

once(emitter, eventName, options)

static once(emitter, eventName, options?): Promise<any[]>

Parameters

• emitter: _DOMEventTarget

• eventName: string

• options?: StaticEventEmitterOptions

Returns

Promise<any[]>

Inherited from

PubSubService.once

Source

packages/core/node_modules/@types/node/events.d.ts:195

setMaxListeners()

static setMaxListeners(n?, ...eventTargets?): void

const {
  setMaxListeners,
  EventEmitter
} = require('events');

const target = new EventTarget();
const emitter = new EventEmitter();

setMaxListeners(5, target, emitter);

Parameters

• n?: number

A non-negative number. The maximum number of listeners per EventTarget event.

• ...eventTargets?: (EventEmitter | _DOMEventTarget)[]

Returns

void

Inherited from

PubSubService.setMaxListeners

Since

v15.4.0

Source

packages/core/node_modules/@types/node/events.d.ts:317

Class: abstract Queue<T, K>

Extends​

Type parameters​

Constructors​

new Queue(webda, name, params)​

Parameters​

Returns​

Inherited from​

Source​

Properties​

_createException​

Inherited from​

Source​

_initException​

Inherited from​

Source​

_initTime​

Inherited from​

Source​

_name​

Inherited from​

Source​

_timeout​

Source​

_webda​

Inherited from​

Source​

delayer​

Source​

eventPrototype​

Returns​

Source​

failedIterations​

Source​

logger​

Inherited from​

Source​

metrics​

Type declaration​

errors​

messages_pending​

messages_received​

messages_sent​

processing_duration​

Inherited from​

Source​

parameters​

Inherited from​

Source​

captureRejectionSymbol​

Inherited from​

Source​

captureRejections​

Inherited from​

Source​

defaultMaxListeners​

Inherited from​

Source​

errorMonitor​

Inherited from​

Source​

Methods​

__clean()​

Returns​

Inherited from​

Abstract​

Source​

addListener()​

Parameters​

Returns​

Inherited from​

Since​

Source​

addRoute()​

Parameters​

Returns​

Inherited from​

Source​

authorizeClientEvent()​

Parameters​

Class: `abstract` Queue<T, K>

Extends

Type parameters

Constructors

new Queue(webda, name, params)

Parameters

Returns

Inherited from

Source

Properties

_createException

Inherited from

Source

_initException

Inherited from

Source

_initTime

Inherited from

Source

_name

Inherited from

Source

_timeout

Source

_webda

Inherited from

Source

delayer

Source

eventPrototype

Returns

Source

failedIterations

Source

logger

Inherited from

Source

metrics

Type declaration

errors

messages_pending

messages_received

messages_sent

processing_duration

Inherited from

Source

parameters

Inherited from

Source

captureRejectionSymbol

Inherited from

Source

captureRejections

Inherited from

Source

defaultMaxListeners

Inherited from

Source

errorMonitor

Inherited from

Source

Methods

__clean()

Returns

Inherited from

Abstract

Source

addListener()

Parameters

Returns

Inherited from

Since

Source

addRoute()

Parameters

Returns

Inherited from

Source

authorizeClientEvent()

Parameters