Keep a node application constantly running

Use PM2 as a process manager

PM2 lets you run your nodejs scripts forever. In the event that your application crashes, PM2 will also restart it for you.

Install PM2 globally to manager your nodejs instances

npm install pm2 -g

Navigate to the directory in which your nodejs script resides and run the following command each time you want to start a nodejs instance to be monitored by pm2:

pm2 start server.js --name "app1"

Useful commands for monitoring the process

1. List all nodejs instances managed by pm2

   pm2 list

2. Stop a particular nodejs instance

`pm2 stop <instance named>`

3. Delete a particular nodejs instance

   pm2 delete <instance name>

4. Restart a particular nodejs instance

   pm2 restart <instance name>

5. Monitoring all nodejs instances

   pm2 monit

6. Stop pm2

   pm2 kill

7. As opposed to restart, which kills and restarts the process, reload achieves a 0-second-downtime reload

   pm2 reload <instance name>

8. View logs

   pm2 logs <instance_name>

Running and stopping a Forever daemon

To start the process:

$ forever start index.js
warn:    --minUptime not set. Defaulting to: 1000ms
warn:    --spinSleepTime not set. Your script will exit if it does not stay up for at least 1000ms
info:    Forever processing file: index.js

List running Forever instances:

$ forever list
info:    Forever processes running

|data: | index | uid | command          | script      |forever pid|id   | logfile                |uptime        |
|------|-------|-----|------------------|-------------|-----------|-----|------------------------|--------------|
|data: | [0]   |f4Kt |/usr/bin/nodejs   | src/index.js|2131       | 2146|/root/.forever/f4Kt.log | 0:0:0:11.485 |

Stop the first process:

$ forever stop 0

$ forever stop 2146

$ forever stop --uid f4Kt

$ forever stop --pidFile 2131

Continuous running with nohup

An alternative to forever on Linux is nohup.

To start a nohup instance

1. cd to the location of app.js or wwwfolder
2. run nohup nodejs app.js &

To kill the process

1. run ps -ef|grep nodejs
2. kill -9 <the process number>

Process Mangement with Forever