smartexit/readme.md

# @push.rocks/smartexit

A library for managing graceful shutdowns of Node.js processes by handling cleanup operations, including terminating child processes.

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## Install

To install `@push.rocks/smartexit`, use pnpm:

```bash
pnpm install @push.rocks/smartexit
```

## Usage

`@push.rocks/smartexit` helps you gracefully shut down Node.js applications by running cleanup operations before the process exits. It handles signal interception (`SIGINT`, `SIGTERM`), uncaught exception management, and child process termination.

### Basic Setup

```typescript
import { SmartExit } from '@push.rocks/smartexit';

// Create an instance - this automatically hooks into process signals
const smartExit = new SmartExit();
```

### Registering Cleanup Functions

Define custom async cleanup functions that execute before the process exits:

```typescript
smartExit.addCleanupFunction(async () => {
  console.log('Closing database connections...');
  await database.close();
});

smartExit.addCleanupFunction(async () => {
  console.log('Flushing logs...');
  await logger.flush();
});
```

### Managing Child Processes

Track spawned child processes so they get properly terminated on exit:

```typescript
import { spawn } from 'child_process';

const childProcess = spawn('node', ['worker.js']);
smartExit.addProcess(childProcess);

// Remove from tracking if the process ends naturally
childProcess.on('exit', () => {
  smartExit.removeProcess(childProcess);
});
```

### Kill Process Trees by PID

Terminate an entire process tree using the static `killTreeByPid` method:

```typescript
import { SmartExit, type TProcessSignal } from '@push.rocks/smartexit';

// Kill with default SIGKILL
await SmartExit.killTreeByPid(12345);

// Kill with a specific signal
await SmartExit.killTreeByPid(12345, 'SIGTERM');
```

### Triggering Cleanup Manually

While `SmartExit` automatically hooks into `SIGINT`, `SIGTERM`, and uncaught exceptions, you can manually trigger cleanup:

```typescript
await smartExit.killAll();
process.exit(0);
```

### Integrating with Express

Gracefully close an Express server on shutdown:

```typescript
import express from 'express';
import { SmartExit } from '@push.rocks/smartexit';

const app = express();
const smartExit = new SmartExit();

const server = app.listen(3000, () => {
  console.log('Server running on port 3000');
});

smartExit.addCleanupFunction(async () => {
  console.log('Closing Express server...');
  await new Promise<void>((resolve) => server.close(() => resolve()));
});
```

### Available Process Signals

The `TProcessSignal` type provides all standard POSIX signals:

```typescript
import type { TProcessSignal } from '@push.rocks/smartexit';

// Examples: 'SIGINT', 'SIGTERM', 'SIGKILL', 'SIGHUP', 'SIGUSR1', 'SIGUSR2', etc.
```

### How It Works

When you create a `SmartExit` instance, it automatically:

1. **Hooks `SIGINT`** (Ctrl+C): Runs cleanup and exits with code 0
2. **Hooks process `exit`**: Runs cleanup when `process.exit(0)` is called
3. **Catches uncaught exceptions**: Logs the error, runs cleanup, and exits with code 1

On `killAll()`, it:
- Sends `SIGINT` to all tracked child processes
- Waits 10 seconds, then sends `SIGKILL` if processes are still alive
- Executes all registered cleanup functions

## License and Legal Information

This repository contains open-source code licensed under the MIT License. A copy of the license can be found in the [LICENSE](./LICENSE) file.

**Please note:** The MIT License does not grant permission to use the trade names, trademarks, service marks, or product names of the project, except as required for reasonable and customary use in describing the origin of the work and reproducing the content of the NOTICE file.

### Trademarks

This project is owned and maintained by Task Venture Capital GmbH. The names and logos associated with Task Venture Capital GmbH and any related products or services are trademarks of Task Venture Capital GmbH or third parties, and are not included within the scope of the MIT license granted herein.

Use of these trademarks must comply with Task Venture Capital GmbH's Trademark Guidelines or the guidelines of the respective third-party owners, and any usage must be approved in writing. Third-party trademarks used herein are the property of their respective owners and used only in a descriptive manner, e.g. for an implementation of an API or similar.

### Company Information

Task Venture Capital GmbH
Registered at District Court Bremen HRB 35230 HB, Germany

For any legal inquiries or further information, please contact us via email at hello@task.vc.

By using this repository, you acknowledge that you have read this section, agree to comply with its terms, and understand that the licensing of the code does not imply endorsement by Task Venture Capital GmbH of any derivative works.