How to monitor a puma server?

Question

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 1

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.