nodejs error restart

With the widespread application of nodejs, program errors and crashes also occur from time to time, which brings a lot of trouble to development and operation and maintenance personnel. Under such circumstances, how to achieve rapid error restart and ensure the stable operation of the program has become one of the issues that developers need to pay attention to.

This article will introduce some common reasons for nodejs errors and how to use pm2 to achieve error restart.

1. The main reasons for NodeJS errors
   There are many reasons for NodeJS errors, the most common of which include the following:

(1) Network connection failure or timeout question. When making network requests, data may not be obtained due to network problems, server failures, high load, etc., causing the program to crash.

(2) Memory leak. When a program is running, if the memory is not managed correctly, a memory leak will occur, causing the program to take up more and more memory, eventually causing the system to crash.

(3) Code writing error. There may be logic errors, grammatical errors and other problems in the writing of the code. These problems may cause the program to fail to run normally and thus crash.

2. PM2 Introduction
   PM2 is a Nodejs process manager in a production environment. It can help developers deploy Nodejs applications with smooth restart, load balancing and 0-second downtime. PM2 has built-in logging, process guarding, cluster mode and other functions, which can help us better manage the Nodejs process.
3. PM2’s error restart function
   PM2’s error restart function can automatically monitor the crash situation of Nodejs applications and automatically restart when the program crashes to ensure the stable operation of the application.

To use the error restart function of PM2, you first need to install PM2:

npm install pm2 -g

After the installation is complete, you can start the application through the following command:

pm2 start app.js

At this time, If the application crashes, PM2 will automatically try to restart the application. If the restart fails, an error message will be output on the console to remind developers to troubleshoot.

4. Operation monitoring function of PM2
   In addition to the automatic restart function, PM2 also provides operation monitoring function. While the application is running, PM2 can monitor the application's running status, CPU, memory and network usage, etc., and output the monitoring results to the console. Through the operation monitoring function, developers can keep abreast of the operation of the application, discover potential problems, and make corresponding optimizations.

To enable PM2's operation monitoring function, you can use the following command:

pm2 monit

At this time, you can use the arrow keys to select the process you want to view and view various operation monitoring data.

5. PM2’s memory leak monitoring function
   In addition to the running monitoring function, PM2 also provides a memory leak monitoring function. By turning on the memory leak monitoring function, you can detect whether the application has memory leak problems and automatically restart the application when a problem is discovered.

To enable PM2's memory leak monitoring function, you can use the following command:

pm2 start app.js --max-memory-restart 50M

At this time, PM2 will monitor the application memory usage. If the memory occupied by the application exceeds 50M, it will The application will automatically restart.

6. Summary
   Through PM2’s error restart function, operation monitoring function and memory leak monitoring function, we can better manage Nodejs applications and ensure the stable operation of the program. When a program crashes or memory leaks, PM2 can automatically detect and restart the application, reducing application downtime and improving program availability.

In the future, with the widespread application of Nodejs, we believe that PM2 will become more and more important and become an important tool for Nodejs process management.

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