pm2 --watch is logging every 3 seconds irrespective of config file - node.js

Question

We have the below config file for pm2:
module.exports = {
apps: [
{
script: 'index.js',
// ------------------------------------ watch options - begin
watch: ['/testing'],
watch_delay: 10000,
ignore_watch: ['node_modules', 'logs'],
watch_options: {
followSymlinks: false,
},
// ------------------------------------ watch options - end
error_file: 'logs/err.log',
out_file: 'logs/out.log',
log_file: 'logs/combined.log',
time: true,
},
],
deploy: {
production: {
user: 'SSH_USERNAME',
host: 'SSH_HOSTMACHINE',
ref: 'origin/master',
repo: 'GIT_REPOSITORY',
path: 'DESTINATION_PATH',
'pre-deploy-local': '',
'post-deploy':
'npm install && pm2 reload ecosystem.config.js --env production',
'pre-setup': '',
},
},
};
With this in place, and a single index.js file:
console.log(`testing`);
We get 'testing printed to the log file every 3 seconds;
2021-05-31T12:02:39: testing
2021-05-31T12:02:42: testing
2021-05-31T12:02:45: testing
2021-05-31T12:02:48: testing
2021-05-31T12:02:51: testing
2021-05-31T12:02:55: testing
There are no changes to the files, and this isn't the logs directory or files being monitored as they're excluded with ignore_watch: ['node_modules', 'logs'],.
Why isn't --watch only monitoring for file changes, and instead logging every 3 seconds?

Answer 1

PM2 is detecting that your app is exiting and restarting your app.
You can choose what PM2 should do when it detects when your app exists, such as --no-autorestart.
Example log output:
$ pm2 --watch --no-autorestart --ignore-watch=node_modules start index.js
$ pm2 logs -f
PM2 | App name:index id:0 online
0|index | testing
PM2 | App [index] with id [0] and pid [48907], exited with code [0] via signal [SIGINT]
# Modify index.js to log `testing 2`.
PM2 | Change detected on path index.js for app index - restarting
PM2 | App name:index id:0 online
0|index | testing 2
PM2 | App [index] with id [0] and pid [48910], exited with code [0] via signal [SIGINT]