Watch not reloading the app in docker

What's going wrong?

When using pm2 on docker, with the watch option, changing a file does not trigger a restart of the application

How could we reproduce this issue?

• Create a simple webapp with nodejs
• Dockerize it with pm2 and use --watch,--ignore-watch='node_modules' arguments
• Enter the container and change a file

Supporting information

--- PM2 report ----------------------------------------------------------------
Date                 : Fri Oct 30 2020 09:28:56 GMT+0000 (Coordinated Universal Time)
===============================================================================
--- Daemon -------------------------------------------------
pm2d version         : 4.5.0
node version         : 12.19.0
node path            : not found
argv                 : /usr/local/bin/node,/usr/local/bin/pm2-runtime,server.js,--watch,--ignore-watch='node_modules'
argv0                : node
user                 : undefined
uid                  : 0
gid                  : 0
uptime               : 5min
===============================================================================
--- CLI ----------------------------------------------------
local pm2            : 4.5.0
node version         : 12.19.0
node path            : /usr/local/bin/pm2
argv                 : /usr/local/bin/node,/usr/local/bin/pm2,report
argv0                : node
user                 : undefined
uid                  : 0
gid                  : 0
===============================================================================
--- System info --------------------------------------------
arch                 : x64
platform             : linux
type                 : Linux
cpus                 : Intel(R) Core(TM) i3-2350M CPU @ 2.30GHz
cpus nb              : 4
freemem              : 3457523712
totalmem             : 6582960128
home                 : /root
===============================================================================
--- PM2 list -----------------------------------------------
┌─────┬───────────┬─────────────┬─────────┬─────────┬──────────┬────────┬──────┬───────────┬──────────┬──────────┬──────────┬──────────┐       
│ id  │ name      │ namespace   │ version │ mode    │ pid      │ uptime │ ↺    │ status    │ cpu      │ mem      │ user     │ watching │       
├─────┼───────────┼─────────────┼─────────┼─────────┼──────────┼────────┼──────┼───────────┼──────────┼──────────┼──────────┼──────────┤       
│ 0   │ server    │ default     │ 1.0.0   │ fork    │ 62       │ 3m     │ 1    │ online    │ 0%       │ 44.9mb   │ root     │ enabled  │       
└─────┴───────────┴─────────────┴─────────┴─────────┴──────────┴────────┴──────┴───────────┴──────────┴──────────┴──────────┴──────────┘       
===============================================================================
--- Daemon logs --------------------------------------------

btw the single restart was manually triggered

Reproduce the issue with a Node.js webapp in Docker using pm2-runtime server.js --watch --ignore-watch='node_modules', then change a file inside the container and observe whether the app restarts. Investigate the PM2 watch behavior in this Docker setup; done means file changes trigger an automatic restart while node_modules remains ignored.