I have a nodejs application running on a live server. I start a new node process using the following command in Terminal of VSCODE by accessing the server through SSH.

nohup node filename.js &

Mostly I can see the process id using the following command in the VSCODE terminal.

netstat -lpn | grep 30001

This command gives the following output:

tcp6       0      0 :::30001                :::*                    LISTEN      21552/node

But, sometimes it doesnt show up any process id, as shown in the following output:

tcp6       0      0 :::30001                :::*                    LISTEN      - 

In case the process dies to due some technical error, it should get restarted automatically. I have executed the following code through a cron in every 5 minutes for this, which works.

const find = require('find-process');
var spawn = require('child_process').spawn;

find("port", "30001")
    .then((list)=> {
        console.log("list::", list);
        if (!list.length) {
            spawn('node', [`${__dirname}/filename.js`], {
                detached: true,
                stdio: 'ignore'
            }).unref();
        }
    }, function (err) {
        console.log(err.stack || err);
    });

Following is my cron

*/5 * * * * node path-to-js-file/crontab.js

My Question:

1. Why my node instance on port 30001 is sometimes not having a pid while the application contained inside it is still accessible?
2. kill -9 will need a Process Id which I dont have as showed above. How to kill such process through command so that it can be restarted?

CodePudding user response：

To show the proccess pid you can use the process module of nodejs.

var process = require('process');
console.log(`Process pid ${process.pid}`);

CodePudding user response：

You can get the parent process id by process.pid. Similarly, when you create a child process using spawn or exec, it returns the child process object and this object contains the child parent id

const find = require('find-process');
var spawn = require('child_process').spawn;

find("port", "30001")
    .then((list)=> {
        console.log("list::", list);
        if (!list.length) {
            const childProcess = spawn('node', [`${__dirname}/filename.js`], {
                detached: true,
                stdio: 'ignore'
            }).unref();

         console.log(`Child Process ${childProcess.pid}`);
        }
    }, function (err) {
        console.log(err.stack || err);
    });