@loopback/docs

--- lang: en title: 'API docs: pooling.poolingservice' keywords: LoopBack 4.0, LoopBack 4, Node.js, TypeScript, OpenAPI sidebar: lb4_sidebar editurl: https://github.com/loopbackio/loopback-next/tree/master/extensions/pooling permalink: /doc/en/lb4/apidocs.pooling.poolingservice.html ---  [Home](./index.md) > [@loopback/pooling](./pooling.md) > [PoolingService](./pooling.poolingservice.md) ## PoolingService class A singleton service to maintain a pool of resources. This pool service can be bound to different keys to represent multiple pools. Each binding is a singleton so that the state stays the same for injections into multiple instances for other artifacts. **Signature:** ```typescript export declare class PoolingService<T> implements LifeCycleObserver ``` **Implements:** [LifeCycleObserver](./core.lifecycleobserver.md) ## Remarks Some resources can be expensive to create/start. For example, a datasource has overhead to connect to the database. There will be performance penalty to use `TRANSIENT` scope and creates a new instance per request. But it is not feasible to be a singleton for some use cases, for example, each request may have different security contexts. The pool service observes life cycle events to start and stop. ## Constructors <table><thead><tr><th> Constructor </th><th> Modifiers </th><th> Description </th></tr></thead> <tbody><tr><td markdown="1"> [(constructor)(context, options)](./pooling.poolingservice._constructor_.md) </td><td markdown="1"> </td><td markdown="1"> Constructs a new instance of the `PoolingService` class </td></tr> </tbody></table> ## Properties <table><thead><tr><th> Property </th><th> Modifiers </th><th> Type </th><th> Description </th></tr></thead> <tbody><tr><td markdown="1"> [context](./pooling.poolingservice.context.md) </td><td markdown="1"> `readonly` </td><td markdown="1"> [Context](./context.context.md) </td><td markdown="1"> </td></tr> <tr><td markdown="1"> [pool](./pooling.poolingservice.pool.md) </td><td markdown="1"> `readonly` </td><td markdown="1"> Pool<T> </td><td markdown="1"> The resource pool </td></tr> </tbody></table> ## Methods <table><thead><tr><th> Method </th><th> Modifiers </th><th> Description </th></tr></thead> <tbody><tr><td markdown="1"> [acquire(requestCtx)](./pooling.poolingservice.acquire.md) </td><td markdown="1"> </td><td markdown="1"> Acquire a new instance </td></tr> <tr><td markdown="1"> [destroy(resource)](./pooling.poolingservice.destroy.md) </td><td markdown="1"> </td><td markdown="1"> Destroy a resource from the pool </td></tr> <tr><td markdown="1"> [release(resource)](./pooling.poolingservice.release.md) </td><td markdown="1"> </td><td markdown="1"> Release the resource back to the pool. </td></tr> <tr><td markdown="1"> [run(task, requestCtx)](./pooling.poolingservice.run.md) </td><td markdown="1"> </td><td markdown="1"> Run the task with an acquired resource from the pool. If task is completed successfully, the resource is returned to the pool. Otherwise, the resource is destroyed. </td></tr> <tr><td markdown="1"> [start()](./pooling.poolingservice.start.md) </td><td markdown="1"> </td><td markdown="1"> Start the pool </td></tr> <tr><td markdown="1"> [stop()](./pooling.poolingservice.stop.md) </td><td markdown="1"> </td><td markdown="1"> Stop the pool </td></tr> </tbody></table>