Introduction to gelf-pro

gelf-pro is a comprehensive Node.js library that simplifies sending logs to a Graylog server using the Graylog Extended Log Format (GELF). By using gelf-pro, developers can easily structure their logs, enhance application monitoring, and improve system debugging processes.

Installation

Before diving into the API, it’s essential to install gelf-pro in your project:

  npm install gelf-pro

Configuration

First, configure gelf-pro to set your Graylog server details:

  
    const gelf = require('gelf-pro');

    gelf.setConfig({
      fields: { facility: 'Node.js app' },
      adapterName: 'tcp',
      adapterOptions: {
        host: '127.0.0.1',
        port: 12201
      }
    });
  

Basic Logging

Now you can log messages with different log levels:

  
    gelf.info('This is an informational message.');
    gelf.warn('This is a warning message.');
    gelf.error('This is an error message.');
  

Custom Fields

You can add custom fields to your log messages:

  
    gelf.info('Custom log message', { userId: 123, sessionId: 'abc123' });
  

Error Handling

Log structured errors for better debugging:

  
    try {
      throw new Error('Something went wrong!');
    } catch (error) {
      gelf.error('An error occurred', {
        errorMessage: error.message,
        stack: error.stack
      });
    }
  

Using in an Express Application

Integrate gelf-pro in an Express.js application:

  
    const express = require('express');
    const gelf = require('gelf-pro');
    
    gelf.setConfig({
      fields: { facility: 'Express.js app' },
      adapterOptions: {
        host: '127.0.0.1',
        port: 12201
      }
    });

    const app = express();

    app.use((req, res, next) => {
      gelf.info('Incoming request', { method: req.method, url: req.url });
      next();
    });

    app.get('/', (req, res) => {
      res.send('Hello World!');
    });

    app.post('/error', (req, res) => {
      try {
        throw new Error('Test error');
      } catch (error) {
        gelf.error('Caught error in POST /error', {
          errorMessage: error.message,
          stack: error.stack
        });
        res.status(500).send('Internal Server Error');
      }
    });

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

Conclusion

In this article, we’ve explored the capabilities of gelf-pro in logging various types of messages and integrating with an Express.js application. Utilizing structured logs with gelf-pro enhances monitoring and debugging, making it an excellent tool for modern application development.

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