If you have a memory leak in your code, finding and plugging it can be a herculean effort. Instead what if you just killed your processes when they got to be too large? The Puma Worker Killer does just that. Similar to Unicorn Worker Killer but for the Puma web server.
Puma worker killer can only function if you have enabled cluster mode or hybrid mode (threads + worker cluster). If you are only using threads (and not workers) then puma worker killer cannot help keep your memory in control.
BTW restarting your processes to controll memory is like putting a bandaid on a gunshot wound, try figuring out the reason you're seeing so much memory bloat derailed benchmarks can help.
In your Gemfile add:
gem 'puma_worker_killer'
Then run $ bundle install
Somewhere in your main process run this code:
# config/initializers/puma_worker_killer.rb
PumaWorkerKiller.start
That's it. Now on a regular basis the size of all Puma and all of it's forked processes will be evaluated and if they're over the RAM threshold will be killed. Don't worry Puma will notice a process is missing a spawn a fresh copy with a much smaller RAM footprint ASAP.
Before calling start
you can configure PumaWorkerKiller
. You can do so using a configure block or calling methods directly:
PumaWorkerKiller.config do |config|
config.ram = 1024 # mb
config.frequency = 5 # seconds
config.percent_usage = 0.98
config.rolling_restart_frequency = 12 * 3600 # 12 hours in seconds
end
PumaWorkerKiller.start
If you start puma as a daemon, to add puma worker killer config into puma config file, rather than into initializers:
Sample like this: (in puma.rb file)
before_fork do
PumaWorkerKiller.config do |config|
config.ram = 1024 # mb
config.frequency = 5 # seconds
config.percent_usage = 0.98
config.rolling_restart_frequency = 12 * 3600 # 12 hours in seconds
end
PumaWorkerKiller.start
end
It is important that you tell your code how much RAM is available on your system. The default is 512 mb (the same size as a Heroku 1x dyno). You can change this value like this:
PumaWorkerKiller.ram = 1024 # mb
By default it is assumed that you do not want to hit 100% utilization, that is if your code is actually using 512 mb out of 512 mb it would be bad (this is dangerously close to swapping memory and slowing down your programs). So by default processes will be killed when they are at 99 % utilization of the value specified in PumaWorkerKiller.ram
. You can change that value to 98 % like this:
PumaWorkerKiller.percent_usage = 0.98
You may want to tune the worker killer to run more or less often. You can adjust frequency:
PumaWorkerKiller.frequency = 20 # seconds
You may want to periodically restart all of your workers rather than simply killing your largest. To do that set:
PumaWorkerKiller.rolling_restart_frequency = 12 * 3600 # 12 hours in seconds
By default PumaWorkerKiller will perform a rolling restart of all your worker processes every 12 hours. To disable, set to false
.
If you're running on a platform like Heroku where it is difficult to measure RAM from inside of a container accurately, you may want to disable the "worker killer" functionality and only use the rolling restart. You can do that by running:
PumaWorkerKiller.enable_rolling_restart
or you can pass in the restart frequency
PumaWorkerKiller.enable_rolling_restart(12 * 3600) # 12 hours in seconds
Make sure if you do this to not accidentally call PumaWorkerKiller.start
as well.
MIT
Open up an issue or ping me on twitter @schneems.