Introduction to gelf-pro for Enhanced Logging in Node.js

Logging is an essential part of any application, especially for those running in production environments. The gelf-pro library is a powerful tool that simplifies logging in Node.js applications, allowing you to send logs to a Graylog server easily. In this guide, we cover various APIs provided by gelf-pro, complete with code snippets and an example application.

Getting Started with gelf-pro

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

  gelf.setConfig({
    fields: {facility: "my-awesome-app"},  // Optional
    filter: [],                             // Optional
    transform: [],                          // Optional
    broadcast: [],                          // Optional
    levels: {
      verbose: 7,
      debug: 6,
      info: 5,
      warn: 4,
      error: 3,
      critical: 2,
      alert: 1,
      emergency: 0
    },
      adapterName: 'tcp', // Currently supported: udp, tcp or aws (default: udp)
      adapterOptions: {
        protocol: 'tcp',  // Optional; Available for UDP
        host: '127.0.0.1', // Optional
        port: 12201        // Optional
      }
  });
  

Basic Logging with gelf-pro

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

Using Custom Fields

  
  gelf.setConfig({
    fields: {facility: "my-awesome-app", customField: "customValue"}
  });

  gelf.info("Message with custom fields");
  

Advanced Logging: Filters and Transforms

  
  const myFilter = (message) => message.short_message !== "ignore me";
  const myTransform = (message) => {
    if (message.short_message === "transform me") {
      message.full_message = "This message was transformed!";
    }
    return message;
  };

  gelf.setConfig({
    filter: [myFilter],
    transform: [myTransform]
  });

  gelf.info("transform me");
  gelf.info("ignore me");
  

Example Application: Logging HTTP Requests

Below is an example of an Express application that logs incoming HTTP requests using gelf-pro.

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

  gelf.setConfig({
    fields: {facility: "my-awesome-app"},
    adapterName: 'tcp',
    adapterOptions: {host: '127.0.0.1', port: 12201}
  });

  const app = express();

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

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

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

In this application, every incoming HTTP request is logged as an info message to the Graylog server, making it easier to monitor and debug your application.

With these powerful features, gelf-pro can greatly enhance the logging capabilities of your Node.js applications, providing better insights and easier debugging.

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