logging-express-mw

A middleware logger for express framework that uses and accepts a customized winston configuration if given one.

Installation

Install logging-express-mw.

npm install logging-express-mw --save

Logging - Basic Example

Express Integeration

In your server code, such as app.js:

const app = require('express')();
const logging = require('logging-express-mw');

// mw to write elegant apis
app.use(logging.middleware());

Usage

The logging middleware can be called in any API functions or other middleware(s) with access to the req object.

For example, we can create a getUser endpoint such as:

function getUser(req, res) {
  req.logger.silly('log level - silly');
  req.logger.debug('log level - debug');
  req.logger.verbose('log level - verbose');
  req.logger.info('log level - info');
  req.logger.warn('log level - warn');
  req.logger.error('log level - error');

  ...
}

Based on default configuration, we will see the following output:

{"message":"log level - info","level":"info"}
{"message":"log level - warn","level":"warn"}
{"message":"log level - error","level":"error"}

Logging - Advanced Configuration

The logging middleware uses winston. Before you initialize this module, you can pass a configuration object to customize logging level, format, and types of log transports.

| Name | Default | Description | | ------------- | ---------------------- | --------------- | | level | 'info' | Log only if info.level less than or equal to this level | priorities | | format | winston.formats.json | Formatting for info messages (see: [Formats]) | | transports | [] (No transports) | Set of logging targets for info messages | | exitOnError | true | If false, handled exceptions will not cause process.exit |

For more information refer to winston documentation at https://github.com/winstonjs/winston/blob/master/README.md

Express Integration

In the example below, we utilize the winston module to create our configuration object for logging-express-mw.

app.js:

const { format, transports } = require('winston');
const { combine, timestamp, label, printf } = format;

const myFormat = printf(info => {
  return `${info.timestamp} [${info.label}] ${info.level}: ${info.message}`;
});

const loggerConfig = {
  level: 'warn',
  format: combine(
    label({ label: 'right meow!' }),
    timestamp(),
    myFormat
  ),
  transport: [
    new transports.Console(),
    new transports.File({ filename: 'combined.log' }),
  ],
}

app.use(logger.middleware(loggerConfig));

Usage

The logging middleware can be called in any API functions or other middleware(s) with access to the req object.

For example, we can create a getUser endpoint such as:

function getUser(req, res) {
  req.logger.silly('log level - silly');
  req.logger.debug('log level - debug');
  req.logger.verbose('log level - verbose');
  req.logger.info('log level - info');
  req.logger.warn('log level - warn');
  req.logger.error('log level - error');

  ...
}

Based on the custom configuration above, we will see the following output:

2017-10-28T22:46:09.853Z [right meow!] silly: log level - silly
2017-10-28T22:46:09.853Z [right meow!] debug: log level - debug
2017-10-28T22:46:09.853Z [right meow!] verbose: log level - verbose
2017-10-28T22:46:09.853Z [right meow!] info: log level - info
2017-10-28T22:46:09.853Z [right meow!] warn: log level - warn
2017-10-28T22:46:09.853Z [right meow!] error: log level - error