How to tell if nodejs has been started

With the development and use of Node.js becoming more and more widespread, many people are using Node.js for development projects. However, in actual use, we sometimes encounter a situation where we are unable to determine whether Node.js has been started. So, how to judge that Node.js has been started?

In fact, there are many ways to determine whether Node.js has been started. Below I will share some of the more commonly used methods based on my own experience.

1. View console output

When we start Node.js, some information will be output in the console, such as "server listening on port 3000", this is Very obvious signal. If you can see this information, Node.js has been started. Of course, this method is only suitable for local test environments. If it is a production environment, we need other methods.

2. Listening port

When Node.js starts, it will listen to a port number, usually 80 or 3000, etc. Before starting Node.js, we can check whether this port is occupied. If the port is not occupied, then Node.js has not been started; if the port is already occupied, then Node.js has been started. Of course, if your project has multiple ports, this method will be more troublesome.

3. Send a request to check the status

We can check the status of Node.js by sending a request to it. If a response is returned, Node.js has been started. This method requires the use of a third-party library, such as the request library.

The code is as follows:

var http = require('http');
var request = require('request');

var server = http.createServer(function(req, res) {
  // 处理请求
});

server.listen(port, function() {
  request('http://localhost:' + port, function(error, response, body) {
    if (!error && response.statusCode == 200) {
      console.log('Node.js 已经启动');
    } else {
      console.log('Node.js 启动失败');
    }
  });
});

4. Use PM2 to manage the process

PM2 is a very good process management tool that can help us manage the Node.js process , including start, stop, restart, etc. When using PM2 to start Node.js, you can set a configuration file, which includes the commands that Node.js will execute after it starts, and you can set a webhook address. When Node.js starts successfully, it will send a request to this webhook. We You can determine whether Node.js has been started based on whether the request is successful.

The configuration file is as follows:

{
  "apps": [
    {
      "name": "my-app",
      "script": "index.js",
      "watch": true,
      "env": {
        "PORT": 3000
      },
      "webhook": "http://localhost:8080"
    }
  ]
}

When we run pm2 start ecosystem.config.js, PM2 will start Node.js. When Node.js starts successfully A request will be sent to http://localhost:8080. We only need to determine whether the request is successful on the server side of this address.

Summary:

The above methods can help us determine whether Node.js has been started. Different methods have different characteristics. We can choose which method to use according to the specific situation. In actual projects, it is recommended to use PM2 to manage the Node.js process, which is more convenient and faster.

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