What is the use of nodejs pm2?

With the rapid development of the Internet, more and more websites and applications need to be run on servers. At this time, we may need a tool that can manage our application and have functions such as monitoring, running, and reloading. The Node.js process manager pm2 is such a tool. This article will introduce the role of Node.js's process manager pm2 and its advantages.

1. The role of pm2
In a production environment, we often need a stable and highly reliable application running solution. In most cases, we need to deploy multiple instances for load balancing. In this process, a tool that can monitor the process and automatically restart is needed. When a process crashes or a problem occurs, pm2 can automatically monitor the program in the background and restart it, allowing the program to maintain long-term stable operation.

pm2 also plays a very important role in deploying Node.js applications. We can hand over the project to pm2 for management, which can automatically install dependencies, start applications, monitor running conditions, automatically restart, etc., making our projects more stable and reliable.

2. Advantages of pm2

1. Multi-process management
   When using Node.js to write applications, we usually use a single-threaded model, so that only one process is needed. Can do all the work. However, as the number of visits increases, the single-process model may face performance bottlenecks and insufficient resources. At this time, we can use pm2 to start multiple processes and distribute the request pressure through load balancing. Compared with single-process mode, multi-process can improve the efficiency and stability of application running.
2. Daemon process
   In Linux or Unix systems, if we want to run a program in the background, we can use nohup or the & symbol to separate it from the shell. However, when the user locks the console or closes the terminal, the program automatically closes. The process started by pm2 will run as a daemon process. It can continue to run in the background and is not affected by user operations.
3. Automatic reloading of applications
   When we modify the source code or configuration file, we need to restart the application for it to take effect. However, in a production environment, frequent manual application restarts may affect user experience and business processing. pm2 can automatically monitor file changes. Once the file changes, it will automatically restart the application to keep our application up to date.
4. Log Management
   In a production environment, we need to record the application log in a file so that it can be tracked and viewed when an exception occurs. pm2 can manage and record logs, and it also provides a set of APIs to help us manage logs.
5. Version Control
   When using pm2 to start an application, we can specify the version of the application, so that the application can be managed and switched based on the version number. When there is a problem with the application, we can quickly switch to the previous version or roll back the operation.

3. How to use pm2

The installation of pm2 is very simple, you only need to install it through the npm command. Enter the following command to install:

npm install pm2 -g

After the installation is complete, use the pm2 start command to start the application, example:

pm2 start app.js

If you start multiple processes, you can specify the number of processes by specifying the -i parameter. . For example:

pm2 start app.js -i 4

pm2 also provides some commonly used commands, such as:

• pm2 restart application name: restart the application
• pm2 reload application name: Reload the application
• pm2 stop Application name: Stop the application
• pm2 list: List all application information started by pm2
• pm2 log: Display all applications Log information

Summary:

pm2 is a very easy-to-use Node.js process manager that can make our Node.js applications run more stable and reliably. Through the multi-process management and automatic reload functions, the operating efficiency and stability of the application can be improved; through the daemon process and log management functions, our applications can always run in the background and logs can be tracked and viewed. When developing and deploying applications using Node.js, we strongly recommend using pm2 for management and deployment.

The above is the detailed content of What is the use of nodejs pm2?. For more information, please follow other related articles on the PHP Chinese website!