Question

output of passenger-memory-stats

----- Passenger processes -----
PID    VMSize    Private  Name
-------------------------------
28572  207.4 MB  ?        Rack: /home/myapp/application
28580  207.0 MB  ?        Rack: /home/myapp/application
28588  206.0 MB  ?        Rack: /home/myapp/application
28648  206.5 MB  ?        Rack: /home/myapp/application
29005  23.0 MB   ?        PassengerWatchdog
29008  100.5 MB  ?        PassengerHelperAgent
29010  43.1 MB   ?        Passenger spawn server
29013  70.8 MB   ?        PassengerLoggingAgent
29053  202.0 MB  ?        Passenger ApplicationSpawner: /home/myapp/application
29105  202.3 MB  ?        Rack: /home/myapp/application
29114  202.3 MB  ?        Rack: /home/myapp/application
29121  202.3 MB  ?        Rack: /home/myapp/application
29130  202.3 MB  ?        Rack: /home/myapp/application
29138  202.3 MB  ?        Rack: /home/myapp/application

That looks like a lot of spawned processes… this is a app currently in development with no one (that I know of) hitting it…

the output of passenger-status

  App root: /home/myapp/application
  * PID: 29105   Sessions: 1    Processed: 0       Uptime: 15m 11s
  * PID: 29114   Sessions: 1    Processed: 0       Uptime: 14m 0s
  * PID: 29121   Sessions: 1    Processed: 0       Uptime: 14m 0s
  * PID: 29130   Sessions: 1    Processed: 0       Uptime: 14m 0s
  * PID: 29138   Sessions: 1    Processed: 0       Uptime: 14m 0s

First, is this normal?

Second, possible causes?

Answer 1

For anyone having this issue of Rails hanging… If you are running on a limited memory VPS, check and make sure you tune your max_pool so that you don’t spawn too many instances of the app for your system to handle. The default is 6 which is apparently too many for memory strapped VPS’s.

Docs about max pool setting:
http://www.modrails.com/documentation/Users%20guide%20Nginx.html#PassengerMaxPoolSize