Скачать или смотреть Solution for Diverting Logs/Errors to Custom Code Execution in PM2

Learn how to effectively handle uncaught exceptions in PM2 by redirecting logs and executing custom code before crashing your Node.js process.
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This video is based on the question https://stackoverflow.com/q/69978797/ asked by the user 'OIRNOIR' ( https://stackoverflow.com/u/14537087/ ) and on the answer https://stackoverflow.com/a/70121522/ provided by the user 'OIRNOIR' ( https://stackoverflow.com/u/14537087/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Handling Uncaught Exceptions in PM2: A Comprehensive Guide

In the world of Node.js applications, managing errors is crucial for maintaining the stability and performance of your applications. When using PM2, a popular process manager for Node.js, you might encounter a situation where you want to log errors in a more sophisticated way before crashing your application. Specifically, you may want to execute custom code when an uncaught exception occurs instead of allowing the process to exit immediately. This guide explores how to achieve that with PM2.

The Challenge

Imagine you're developing a Node.js application, and you want to catch unhandled exceptions globally. Traditional methods, such as using process.on("uncaughtException", ...), work fine when running plain Node.js applications. However, with PM2, this approach doesn't function as expected. Essentially, here’s what you might be looking to accomplish:

Log the Error: Execute custom logging or error handling code.

Exit the Process: Then, safely exit the application to prevent further issues.

The Solution

After a week of experimentation, I discovered a method that successfully integrates with PM2. Below are the steps you need to follow to handle uncaught exceptions and log them properly before letting the application crash.

Step 1: Require PM2

First, make sure you include PM2 in your application by requiring it at the beginning of your file:

[[See Video to Reveal this Text or Code Snippet]]

Step 2: Launch PM2 Bus

The PM2 bus allows you to listen to various event hooks that PM2 provides. By launching the bus, you can listen directly for process exceptions. Your code should look like this:

[[See Video to Reveal this Text or Code Snippet]]

Step 3: Implement Custom Logging

Next, implement the logTheErrorSomehow() function to handle the logging of your errors. This could involve saving the error message to a file or sending it to an external logging service. Here’s a simple placeholder implementation:

[[See Video to Reveal this Text or Code Snippet]]

Step 4: Test Your Implementation

Once your code is structured this way, you can test it by triggering an uncaught exception in your application. Watch for the logs and ensure that your custom logging function executes correctly before the process exits. You should see the expected error log in your output.

Conclusion

This solution will allow you to divert logs and errors to your custom code execution within a PM2-managed Node.js application, effectively managing uncaught exceptions while providing insights into failures. By utilizing PM2's bus capabilities, you can transition from a direct process crash to a more graceful error handling approach.

By following the steps outlined in this guide, you can enhance the robustness of your application and have better control over how errors are managed. Happy coding!