Feature request: Be able to change assets:precompile CPU priority

We sometimes hit an issue where the Webpack compile part of the assets:precompile takes enough CPU that it causes response times to go up noticeably.

I created a workaround by running assets:precompile under a lower CPU priority using nice. I chose nice because

It is always available on Linux/unix AFAIK
It correctly changes the priority of and child processes spawned by assets:precompile (unlike things like cpulimit)
It is a lot less faff to implement than cgroups etc.

I'm guessing I'm not the only person who has hit this issue so I think it could potentially be useful to have this as an (opt-in, turned on via config) part of this gem.

I am happy to work up a PR if this is something the core team would consider.

# config/deploy.rb

###
# The capistrano-rails gem provides a `deploy:assets:precompile` task. We
# override that task here because we want to run `bundle exec rails assets:precompile`
# with a lower CPU priority than other processes on the system so that it
# doesn't take CPU away from the running puma processes.
#
# We use the unix `nice` command to achieve this ("man nice" for help). Nice's
# process priorities range from -19 (highest priority) to +20 (lowest priority).
# Processes on Ubuntu have a "nice value" of 0 by default so we choose a
# priority of "3" which is slightly lower than other processes.
#
Rake::Task["deploy:assets:precompile"].clear_actions
namespace :deploy do
  namespace :assets do
    task :precompile do
      on release_roles(fetch(:assets_roles)) do
        within release_path do
          with rails_env: fetch(:rails_env), rails_groups: fetch(:rails_assets_groups) do
            execute "nice", "-n", "3", "bundle", "exec", "rails", "assets:precompile"
          end
        end
      end
    end
  end
end

capistrano / rails

Feature request: Be able to change assets:precompile CPU priority #258