Is there a way to monitor the status of a puma server? most specifically, how many busy workers it has and how many threads each worker provisioned. best would be something similar to apache's mod_status
Answer
Maybe
$ touch /path/to/your/stats.txt
$ puma -S /path/to/your/stats.txt
in another terminal
$ watch cat /path/to/your/stats.txt
Results in:
---
pid: 14364
config: !ruby/object:Puma::Configuration
cli_options:
conf:
options:
:min_threads: 0
:max_threads: 16
:quiet: false
:debug: false
:binds:
- tcp://0.0.0.0:9292
:workers: 0
:daemon: false
:mode: :http
:before_fork: []
:worker_timeout: 60
:worker_boot_timeout: 60
:worker_shutdown_timeout: 30
:state: /path/to/your/stats.txt
:config_file:
:control_auth_token: 21c9241912a8e0e7ddaabac667ff5682
:tag: solar
:environment: development
But that looks static :(
Starting your app via puma like this:
$ puma -S /path/to/your/stats.txt -C config/puma.rb --control tcp://0.0.0.0:9191 --control-token foo config.ru
allows you later to query per your webbrowser:
$ http://localhost:9191/stats?token=foo
or
$ pumactl -C tcp://0.0.0.0:9191 -T foo stats
Resulting in:
{ "workers": 3, "phase": 0, "booted_workers": 3 }
Which looks more dynamic...
Edit_0:
As workers are processes, one could also leverage tools provided by the operating system to gather information, e.g. on Linux:
Starting a puma instance:
puma -S p/stats.txt -C config/puma.rb --control tcp://0.0.0.0:9191 --control-token foo config.ru
[1908] Puma starting in cluster mode...
[1908] * Version 2.15.3 (ruby 2.1.5-p273), codename: Autumn Arbor Airbrush
[1908] * Min threads: 8, max threads: 32
[1908] * Environment: development
[1908] * Process workers: 3
[1908] * Preloading application
[1908] * Listening on tcp://0.0.0.0:9292
[1908] Use Ctrl-C to stop
[1908] * Starting control server on tcp://0.0.0.0:9191
[1908] - Worker 0 (pid: 1921) booted, phase: 0
[1908] - Worker 1 (pid: 1929) booted, phase: 0
[1908] - Worker 2 (pid: 1937) booted, phase: 0
Using top to investigate workers:
$ top -p1921 -p1929 -p1937 -n 1
gives us
Tasks: 3 total, 0 running, 3 sleeping, 0 stopped, 0 zombie
%Cpu(s): 8.4 us, 1.5 sy, 0.0 ni, 88.9 id, 1.2 wa, 0.0 hi, 0.0 si, 0.0 st
KiB Mem: 4058820 total, 1626576 used, 2432244 free, 56456 buffers
KiB Swap: 9609212 total, 0 used, 9609212 free. 424948 cached Mem
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
1921 benjamin 20 0 1171600 85484 3116 S 0.0 2.1 0:00.38 puma
1929 benjamin 20 0 1171600 85264 2884 S 0.0 2.1 0:00.37 puma
1937 benjamin 20 0 1171600 85264 2884 S 0.0 2.1 0:00.42 puma
from which one can parse out relevant information like CPU or RAM utilization.