File: //var/www/api-storage/node_modules/piscina/docs/docs/api-reference/api-overview.md
---
id: API Overview
sidebar_position: 1
---
| API | Description |
| ---------------------------------------------------------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| **Class: `Piscina`** | This class extends [`EventEmitter`](https://nodejs.org/api/events.html#events_class_eventemitter) from Node.js. |
| **Constructor: `new Piscina([options])`** | Creates a new instance of the `Piscina` class. [List of available options](./class.md) |
| **Method: `run(task[, options])`** | Schedules a task to be run on a Worker thread. |
| **Method: `runTask(task[, transferList][, filename][, abortSignal])`** | **Deprecated** -- Use `run(task, options)` instead. |
| **Method: `destroy()`** | Stops all Workers and rejects all `Promises` for pending tasks. |
| **Method: `close([options])`** | Stops all Workers gracefully. |
| **Event: `'error'`** | Emitted when uncaught exceptions occur inside Worker threads or unexpected messages are sent from Worker threads. |
| **Event: `'drain'`** | Emitted whenever the `queueSize` reaches `0`. |
| **Event: `'needsDrain'`** | Triggered once the total capacity of the pool is exceeded by the number of tasks enqueued that are pending execution. |
| **Event: `'message'`** | Emitted whenever a message is received from a worker thread. |
| **Property: `completed` (readonly)** | The current number of completed tasks. |
| **Property: `duration` (readonly)** | The length of time (in milliseconds) since this `Piscina` instance was created. |
| **Property: `options` (readonly)** | A copy of the options that are currently being used by this instance. |
| **Property: `runTime` (readonly)** | A histogram summary object summarizing the collected run times of completed tasks. |
| **Property: `threads` (readonly)** | An Array of the `Worker` instances used by this pool. |
| **Property: `queueSize` (readonly)** | The current number of tasks waiting to be assigned to a Worker thread. |
| **Property: `needsDrain` (readonly)** | Boolean value that specifies whether the capacity of the pool has been exceeded by the number of tasks submitted. |
| **Property: `utilization` (readonly)** | A point-in-time ratio comparing the approximate total mean run time of completed tasks to the total runtime capacity of the pool. |
| **Property: `waitTime` (readonly)** | A histogram summary object summarizing the collected times tasks spent waiting in the queue. |
| **Static Property: `isWorkerThread` (readonly)** | Is `true` if this code runs inside a `Piscina` threadpool as a Worker. |
| **Static Property: `version` (readonly)** | Provides the current version of this library as a semver string. |
| **Static Method: `move(value)`** | By default, any value returned by a worker function will be cloned when returned back to the Piscina pool, even if that object is capable of being transferred. The `Piscina.move()` method can be used to wrap and mark transferable values such that they will be transferred rather than cloned. |
| **Interface: `Transferable`** | Objects may implement the `Transferable` interface to create their own custom transferable objects. |