# callBeforeAppShutdownHook

**Kind:** Function

**Source:** [`packages/core/hooks/before-app-shutdown.hook.ts`](https://github.com/nestjs/nest/blob/master/packages/core/hooks/before-app-shutdown.hook.ts#L49)

**Part of:** [Core](subsystem-packages-core)

Calls the `beforeApplicationShutdown` function on the module and its children
(providers / controllers).

`callBeforeAppShutdownHook` invokes the `beforeApplicationShutdown` lifecycle hook for a module’s providers, controllers, and module class. It coordinates shutdown hook execution for static dependency trees and forwards the optional operating-system shutdown signal to each eligible instance.

## Signature

```ts
async function callBeforeAppShutdownHook(module: Module, signal: string): Promise<void>
```

## Parameters

| Name | Type |
|---|---|
| `module` | `Module` |
| `signal` | `string` |

**Returns:** `Promise<void>`

## Diagram

```mermaid
graph LR
  A[Application shutdown signal] --> B[callBeforeAppShutdownHook]
  B --> C[Module providers]
  B --> D[Module controllers]
  B --> E[Module class instance]
  C --> F[beforeApplicationShutdown(signal)]
  D --> F
  E --> F
```

## Usage

```ts
import { callBeforeAppShutdownHook } from '@nestjs/core/hooks/before-app-shutdown.hook';
import { ModulesContainer } from '@nestjs/core';

async function runShutdownHooks(
  modulesContainer: ModulesContainer,
  signal = 'SIGTERM',
) {
  for (const moduleRef of modulesContainer.values()) {
    await callBeforeAppShutdownHook(moduleRef, signal);
  }
}
```

## AI Coding Instructions

- Preserve the lifecycle execution order: providers and controllers should run before the module class hook.
- Always forward the optional shutdown signal, such as `SIGTERM` or `SIGINT`, to `beforeApplicationShutdown`.
- Await hook execution so asynchronous cleanup tasks, such as closing database connections, finish before shutdown continues.
- Only invoke hooks for eligible static dependency trees; transient or request-scoped instances require the existing instance-selection logic.
- Treat this as framework lifecycle infrastructure—prefer enabling application shutdown hooks rather than calling it directly in application code.

## Relationships

- IMPORTS → `BeforeApplicationShutdown`
- IMPORTS → `isFunction`
- IMPORTS → `isNil`