Nodejs throws an error twice and hangs

With the development of Node.js, it has become a very popular back-end framework, which is widely used in server-side development and web application development. However, sometimes you may encounter the problem of "nodejs throws an error twice and hangs".

Node.js is an event-driven framework that allows developers to write code under a non-blocking I/O model. This model shows high performance and scalability, so in most cases you can see Node.js applications used as the backend of high-performance web services.

Due to the internal design of Node.js, if an uncaught exception is thrown during program execution, the program will stop running. This means you must write code to catch and handle exceptions, otherwise your Node.js application may crash due to it.

For most Node.js applications, catching exceptions is a fairly simple task. You just need to set up a try-catch block in your code or listen for the "error" event.

However, in some cases, Node.js may use modules with different control behaviors, such as the Domain module. At this time, when the program throws an uncaught exception, the program will not stop running immediately. Instead, the program will wait until the next tick in the event loop to stop.

In this case, if the exception in the application is caught and re-thrown, you can observe the problem of "nodejs throws an error twice and hangs". That is, if the same exception is thrown more than twice in a row, the application will stop running.

This detail is not clearly stated in the official documentation of Node.js, so we need to conduct a more careful and in-depth analysis of the code to understand it.

So, how to solve the problem of "nodejs throws an error twice and hangs"?

The best approach is to always avoid throwing uncaught exceptions. For Node.js applications, you should always implement the following good practices:

1. Enforce exception handling

Add try-catch blocks when writing code to handle possible Code that throws an exception. This will make your code more robust and more fault-tolerant.

2. Handling exceptions at the process level

You can also use another strategy which involves using a process.on('uncaughtException') listener at the process level Catch all unhandled exceptions. In addition to catching exceptions, this method also provides some other advantages, such as logging error information and stack traces when uncatchable exceptions occur.

3. Avoid using the obsolete Domain module

The Domain module is an obsolete module in Node.js that has been deprecated. Instead, you can use the Async Hooks API to catch and handle exceptions in asynchronous calls.

Summary

When writing Node.js applications, you always need to handle exceptions carefully and work hard to avoid unhandled exceptions. If you see the "nodejs throws error twice and hangs" problem, you must carefully analyze your code and find out where the problem lies.

Whether you use a try-catch block, or register a process.on('uncaughtException') listener, you should add exception handling logic to your application and ensure that your code can be efficient and fault-tolerant. Also, always use the latest Node.js version and avoid using outdated modules, this will ensure that your code is always in tip-top shape.

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