Phusion Passenger process stuck on (forking...) Rails

Question

Today I updated to the newest updated package for Nginx and Passenger. After the update, my app now has a (forking...) process that wasn't there before and doesn't seem to go away. Yet it is taking up memory and sudo /usr/sbin/passenger-memory-stats reports the following.

--------- Nginx processes ----------
PID   PPID  VMSize    Private  Name
------------------------------------
1338  1     186.0 MB  0.8 MB   nginx: master process /usr/sbin/nginx -g daemon on; master_process on;
1345  1338  186.3 MB  1.1 MB   nginx: worker process
### Processes: 2
### Total private dirty RSS: 1.91 MB


---- Passenger processes -----
PID   VMSize    Private  Name
------------------------------
1312  378.8 MB  2.1 MB   Passenger watchdog
1320  663.8 MB  4.2 MB   Passenger core
1768  211.5 MB  29.0 MB  Passenger AppPreloader: /home/ubuntu/my-app
1987  344.1 MB  52.2 MB  Passenger AppPreloader: /home/ubuntu/my-app (forking...)
2008  344.2 MB  41.1 MB  Passenger AppPreloader: /home/ubuntu/my-app (forking...)
### Processes: 5
### Total private dirty RSS: 128.62 MB

I have the passenger_max_pool_size 2. sudo /usr/sbin/passenger-status reports that two are currently open. The server is receiving no hits at the moment besides me using the site.

Version : 5.3.0
Date    : 2018-05-14 00:41:05 +0000
Instance: ql2TTnkw (nginx/1.14.0 Phusion_Passenger/5.3.0)

----------- General information -----------
Max pool size : 2
App groups    : 1
Processes     : 2
Requests in top-level queue : 0

----------- Application groups -----------
/home/ubuntu/my-app (production):
  App root: /home/ubuntu/my-app
  Requests in queue: 0
  * PID: 1987    Sessions: 0       Processed: 1       Uptime: 3m 36s
    CPU: 0%      Memory  : 52M     Last used: 3m 36s ago
  * PID: 2008    Sessions: 0       Processed: 1       Uptime: 3m 35s
    CPU: 0%      Memory  : 41M     Last used: 3m 35s ago

Passenger never did this before the update and keeps the (forking...) always there now and it seems to have two apps running when it only needs one. I have searched their documents and know when it uses forking and when it doesn't and when it kills app automatically after a certain amount of time. Did they update something with the newest update that I missed in the docs? It seems that 2008 344.2 MB 89.4 MB Passenger AppPreloader: /home/ubuntu/my-app (forking...) always shows now and sometimes even has two of those when before the update I always had the process show without the (forking...).

Answer 1

This is normal for Passenger >= 5.3.

Source: I'm a dev at Phusion who works on Passenger.