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id AsyncQueuer
title AsyncQueuer

Class: AsyncQueuer<TValue>

Defined in: async-queuer.ts:315

A flexible asynchronous queue for processing tasks with configurable concurrency, priority, and expiration.

Async vs Sync Versions: The async version provides advanced features over the sync Queuer:

  • Returns promises that can be awaited for task results
  • Built-in retry support via AsyncRetryer integration for each queued task
  • Abort support to cancel in-flight task executions
  • Comprehensive error handling with onError callbacks and throwOnError control
  • Detailed execution tracking (success/error/settle counts)
  • Concurrent execution support (process multiple items simultaneously)

The sync Queuer is lighter weight and simpler when you don't need async features, return values, or execution control.

What is Queuing? Queuing is a technique for managing and processing items sequentially or with controlled concurrency. Tasks are processed up to the configured concurrency limit. When a task completes, the next pending task is processed if the concurrency limit allows.

Key Features:

  • Priority queue support via the getPriority option
  • Configurable concurrency limit
  • Callbacks for task success, error, completion, and queue state changes
  • FIFO (First In First Out) or LIFO (Last In First Out) queue behavior
  • Pause and resume processing
  • Item expiration to remove stale items from the queue

Error Handling:

  • If an onError handler is provided, it will be called with the error and queuer instance
  • If throwOnError is true (default when no onError handler is provided), the error will be thrown
  • If throwOnError is false (default when onError handler is provided), the error will be swallowed
  • Both onError and throwOnError can be used together; the handler will be called before any error is thrown
  • The error state can be checked using the AsyncQueuer instance

State Management:

  • Uses TanStack Store for reactive state management
  • Use initialState to provide initial state values when creating the async queuer
  • Use onSuccess callback to react to successful task execution and implement custom logic
  • Use onError callback to react to task execution errors and implement custom error handling
  • Use onSettled callback to react to task execution completion (success or error) and implement custom logic
  • Use onItemsChange callback to react to items being added or removed from the queue
  • Use onExpire callback to react to items expiring and implement custom logic
  • Use onReject callback to react to items being rejected when the queue is full
  • The state includes error count, expiration count, rejection count, running status, and success/settle counts
  • State can be accessed via asyncQueuer.store.state when using the class directly
  • When using framework adapters (React/Solid), state is accessed from asyncQueuer.state

Example usage:

const asyncQueuer = new AsyncQueuer<string>(async (item) => {
  // process item
  return item.toUpperCase();
}, {
  concurrency: 2,
  onSuccess: (result) => {
    console.log(result);
  }
});

asyncQueuer.addItem('hello');
asyncQueuer.start();

Type Parameters

TValue

TValue

Constructors

Constructor

new AsyncQueuer<TValue>(fn, initialOptions): AsyncQueuer<TValue>;

Defined in: async-queuer.ts:327

Parameters

fn

(item) => Promise<any>

initialOptions

AsyncQueuerOptions<TValue> = {}

Returns

AsyncQueuer<TValue>

Properties

asyncRetryers

asyncRetryers: Map<number, AsyncRetryer<(item) => Promise<any>>>;

Defined in: async-queuer.ts:321

fn()

fn: (item) => Promise<any>;

Defined in: async-queuer.ts:328

Parameters

item

TValue

Returns

Promise<any>

key

key: string | undefined;

Defined in: async-queuer.ts:319

options

options: AsyncQueuerOptions<TValue>;

Defined in: async-queuer.ts:320

store

readonly store: Store<Readonly<AsyncQueuerState<TValue>>>;

Defined in: async-queuer.ts:316

Methods

abort()

abort(): void;

Defined in: async-queuer.ts:840

Aborts all ongoing executions with the internal abort controllers. Does NOT clear out the items.

Returns

void

addItem()

addItem(
   item, 
   position, 
   runOnItemsChange): boolean;

Defined in: async-queuer.ts:478

Adds an item to the queue. If the queue is full, the item is rejected and onReject is called. Items can be inserted based on priority or at the front/back depending on configuration.

Parameters

item

TValue

position

QueuePosition = ...

runOnItemsChange

boolean = true

Returns

boolean

Example

queuer.addItem({ value: 'task', priority: 10 });
queuer.addItem('task2', 'front');

clear()

clear(): void;

Defined in: async-queuer.ts:805

Removes all pending items from the queue. Does NOT affect active tasks.

Returns

void

execute()

execute(position?): Promise<any>;

Defined in: async-queuer.ts:613

Removes and returns the next item from the queue and executes the task function with it.

Parameters

position?

QueuePosition

Returns

Promise<any>

Example

queuer.execute();
// LIFO
queuer.execute('back');

flush()

flush(numberOfItems, position?): Promise<void>;

Defined in: async-queuer.ts:661

Processes a specified number of items to execute immediately with no wait time If no numberOfItems is provided, all items will be processed

Parameters

numberOfItems

number = ...

position?

QueuePosition

Returns

Promise<void>

flushAsBatch()

flushAsBatch(batchFunction): Promise<void>;

Defined in: async-queuer.ts:675

Processes all items in the queue as a batch using the provided function as an argument The queue is cleared after processing

Parameters

batchFunction

(items) => Promise<any>

Returns

Promise<void>

getAbortSignal()

getAbortSignal(executeCount?): AbortSignal | null;

Defined in: async-queuer.ts:830

Returns the AbortSignal for a specific execution. If no executeCount is provided, returns the signal for the most recent execution. Returns null if no execution is found or not currently executing.

Parameters

executeCount?

number

Optional specific execution to get signal for

Returns

AbortSignal | null

Example

const queuer = new AsyncQueuer(
  async (item: string) => {
    const signal = queuer.getAbortSignal()
    if (signal) {
      const response = await fetch(`/api/process/${item}`, { signal })
      return response.json()
    }
  },
  { concurrency: 2 }
)

getNextItem()

getNextItem(position): TValue | undefined;

Defined in: async-queuer.ts:561

Removes and returns the next item from the queue without executing the task function. Use for manual queue management. Normally, use execute() to process items.

Parameters

position

QueuePosition = ...

Returns

TValue | undefined

Example

// FIFO
queuer.getNextItem();
// LIFO
queuer.getNextItem('back');

peekActiveItems()

peekActiveItems(): TValue[];

Defined in: async-queuer.ts:767

Returns the items currently being processed (active tasks).

Returns

TValue[]

peekAllItems()

peekAllItems(): TValue[];

Defined in: async-queuer.ts:760

Returns a copy of all items in the queue, including active and pending items.

Returns

TValue[]

peekNextItem()

peekNextItem(position): TValue | undefined;

Defined in: async-queuer.ts:750

Returns the next item in the queue without removing it.

Parameters

position

QueuePosition = 'front'

Returns

TValue | undefined

Example

queuer.peekNextItem(); // front
queuer.peekNextItem('back'); // back

peekPendingItems()

peekPendingItems(): TValue[];

Defined in: async-queuer.ts:774

Returns the items waiting to be processed (pending tasks).

Returns

TValue[]

reset()

reset(): void;

Defined in: async-queuer.ts:851

Resets the queuer state to its default values

Returns

void

setOptions()

setOptions(newOptions): void;

Defined in: async-queuer.ts:372

Updates the queuer options. New options are merged with existing options.

Parameters

newOptions

Partial<AsyncQueuerOptions<TValue>>

Returns

void

start()

start(): void;

Defined in: async-queuer.ts:781

Starts processing items in the queue. If already running, does nothing.

Returns

void

stop()

stop(): void;

Defined in: async-queuer.ts:791

Stops processing items in the queue. Does not clear the queue.

Returns

void