egg-logger/README.md

egg logger

# egg-logger

[![NPM version][npm-image]][npm-url]
[![CI](https://github.com/eggjs/egg-logger/actions/workflows/nodejs.yml/badge.svg)](https://github.com/eggjs/egg-logger/actions/workflows/nodejs.yml)
[![Test coverage][codecov-image]][codecov-url]
[![Known Vulnerabilities][snyk-image]][snyk-url]
[![npm download][download-image]][download-url]
[![Node.js Version](https://img.shields.io/node/v/egg-logger.svg?style=flat)](https://nodejs.org/en/download/)

[npm-image]: https://img.shields.io/npm/v/egg-logger.svg?style=flat-square
[npm-url]: https://npmjs.org/package/egg-logger
[codecov-image]: https://codecov.io/github/eggjs/egg-logger/coverage.svg?branch=master
[codecov-url]: https://codecov.io/github/eggjs/egg-logger?branch=master
[snyk-image]: https://snyk.io/test/npm/egg-logger/badge.svg?style=flat-square
[snyk-url]: https://snyk.io/test/npm/egg-logger
[download-image]: https://img.shields.io/npm/dm/egg-logger.svg?style=flat-square
[download-url]: https://npmjs.org/package/egg-logger

Egg logger.

![diagram](diagram.png)

Including two base class, `Logger` and `Transport`:

- Transport: Save log to file, stdout/stderr and network.
- Logger: A logger can contains multi transports.

---

## Install

```bash
$ npm i egg-logger
```

## Usage

Create a `Logger` and add a file `Transport`.

```js
const Logger = require('egg-logger').Logger;
const FileTransport = require('egg-logger').FileTransport;
const ConsoleTransport = require('egg-logger').ConsoleTransport;

const logger = new Logger();
logger.set('file', new FileTransport({
  file: '/path/to/file',
  level: 'INFO',
}));
logger.set('console', new ConsoleTransport({
  level: 'DEBUG',
}));
logger.debug('debug foo'); // only output to stdout
logger.info('info foo');
logger.warn('warn foo');
logger.error(new Error('error foo'));
```

### Enable / Disable Transport

```js
logger.disable('file');
logger.info('info'); // output nothing
logger.enable('file');
logger.info('info'); // output 'info' string
```

### Duplicate

Duplicate error log to other logger.

Accept an `options.excludes` to special whether excludes some tranports.

```js
logger.duplicate('error', errorLogger, { excludes: [ 'console' ]});
logger.error(new Error('print to errorLogger')); // will additional call `errorLogger.error`
```

### Redirect

Redirect special level log to other logger.

```js
oneLogger.redirect('debug', debugLogger); // all debug level logs of `oneLogger` will delegate to debugLogger
```

### Reload

```js
logger.reload(); // will close the exists write stream and create a new one.
```

### Custom Transport

You can make your own `Transport` for logging，e.g.: send log to your logging server.

```js
const urllib = require('urllib');
const Transport = require('egg-logger').Transport;

class UrllibTransport extends Transport {

  log(level, args, meta) {
    const msg = super.log(level, args, meta);
    return urllib.request('url?msg=' + msg);
  }
}

const logger = new Logger();
logger.set('remote', new UrllibTransport({
  level: 'DEBUG',
}));
logger.info('info');
```

## Console logger level

set environment NODE_CONSOLE_LOGGRE_LEVEL = 'INFO' | 'WARN' | 'ERROR'

## License

[MIT](LICENSE)

## Contributors

[![Contributors](https://contrib.rocks/image?repo=eggjs/egg-logger)](https://github.com/eggjs/egg-logger/graphs/contributors)

Made with [contributors-img](https://contrib.rocks).