I want to restart my Node.Js app using PM2 through
pm2 restart app.js
using crontab but ONLY if the app is not already running (e.g. if my server crashed and restarted and pm2 didn't restart).
the command above restarts it anyway even if it's running.
How do I fix it?
UPDATE
I do not want my app to restart if it's already running. I want it to restart only if it's listed as "stopped" or if it is not running. Some suggestions offer to write a bash script, but what would it be? I tried the options below, but they either don't work or restart the app even if it's running.
Instead of launching the pm2 process within the cron, launch a bashscript which checks if the pm2 is already running and restarts it if it's not the case.
Edit
Try following (it might be that the pgrep expression needs to be adjusted, I don't know the exact name of the pm2 process):
#!/bin/bash pID=$(pgrep -x "pm2") if [ -n "${pID}" ]; then #do nothing echo $pID "already running. not restarting." else # start it echo "restarting" # put your command to start your process here fi
The better way of doing it is use the pm2 startup command
http://pm2.keymetrics.io/docs/usage/startup/
To get the automatically-configured startup script for your machine you need to type this command:
# Detect available init system, generate configuration and enable startup system pm2 startup
You can specify the platform you use by yourself if you want to (where platform can be either one of the cited above):
pm2 startup [ubuntu | ubuntu14 | ubuntu12 | centos | centos6 | arch | oracle | amazon | macos | darwin | freebsd | systemd | systemv | upstart | launchd | rcd | openrc]
The output of this command can be a recommendation of the line to copy/paste with all environment variables and options configured for you.
Example:
[PM2] You have to run this command as root. Execute the following command: sudo su -c "env PATH=$PATH:/home/unitech/.nvm/versions/node/v4.3/bin pm2 startup -u --hp
You simply have to copy/paste the line PM2 gives you and the startup script will be configured for your OS.
Once you run the sudo pm2 startup. It will create the systemctl service. You can check the status of the same using
systemctl status pm2-root
By default the service is not configure to restart automatically. You will run the below commands
sudo mkdir -p /etc/systemd/system/pm2-root.service.d
and then create a file name 10_auto_restart_pm2.conf with below content
[Service] Restart=always RestartSec=3
After that execute
systemctl daemon-reload systemctl restart pm2-service
Now let's test the auto restart part
$ systemctl status pm2-root.service ● pm2-root.service - PM2 process manager Loaded: loaded (/etc/systemd/system/pm2-root.service; enabled; vendor preset: enabled) Drop-In: /etc/systemd/system/pm2-root.service.d └―10_auto_restart_pm2.conf Active: active (running) since Wed 2018-02-28 16:52:19 UTC; 11s ago Docs: https://pm2.keymetrics.io/ Process: 5014 ExecStop=/usr/local/lib/node_modules/pm2/bin/pm2 kill (code=exited, status=0/SUCCESS) Process: 5022 ExecStart=/usr/local/lib/node_modules/pm2/bin/pm2 resurrect (code=exited, status=0/SUCCESS) Main PID: 5031 (PM2 v2.10.1: Go) Tasks: 9 Memory: 24.3M CPU: 460ms CGroup: /system.slice/pm2-root.service └―5031 PM2 v2.10.1: God Daemon (/home/vagrant/.pm2)
Now we kill the process manually and wait for 3 seconds
$ kill -9 5031 $ sleep 3 $ systemctl status pm2-root.service ● pm2-root.service - PM2 process manager Loaded: loaded (/etc/systemd/system/pm2-root.service; enabled; vendor preset: enabled) Drop-In: /etc/systemd/system/pm2-root.service.d └―10_auto_restart_pm2.conf Active: active (running) since Wed 2018-02-28 16:52:55 UTC; 641ms ago Docs: https://pm2.keymetrics.io/ Process: 5057 ExecStop=/usr/local/lib/node_modules/pm2/bin/pm2 kill (code=exited, status=0/SUCCESS) Process: 5081 ExecStart=/usr/local/lib/node_modules/pm2/bin/pm2 resurrect (code=exited, status=0/SUCCESS) Main PID: 5088 (PM2 v2.10.1: Go) Tasks: 9 Memory: 24.3M CPU: 461ms CGroup: /system.slice/pm2-root.service └―5088 PM2 v2.10.1: God Daemon (/home/vagrant/.pm2)
As you can see the process/service was restarted automatically. No cron needed and it is how you should do it.
What you're looking to do is start any stopped apps without incurring downtime. A good solution is to use the pm2 startOrReload command. This will start any stopped apps, and will reload any current apps without incurring downtime.
You'll need a config file for the command. if you don't currently have one you can create it using pm2 ecosystem. Make sure it points to app.js.
Then run this command in your cron job:
pm2 startOrReload <your ecosystem file>
See pm2 -h, pm2 startOrReload -h, and pm2 ecosystem -h for more options.
