whenever.rb is a nice DSL for configuring cron tasks in ruby ( https://github.com/javan/whenever )
however, it has a major flaw: all the tasks it runs under cron use the same unix priority, and by 'priority' we mean the one that takes yer boxen down
fortunately, this is easy to fix
step one, replace // configure the job templates in your ./config/schedule.rb file to look something like this
# Learn more: http://github.com/javan/whenever job_type :rake, "cd :path && RAILS_ENV=:environment :environment_variable=:environment nice -n 19 bundle exec rake :task --silent :output" job_type :runner, "cd :path && nice -n 19 ./bin/rails runner -e :environment ':task' :output"
step two: profit
for those of you that don't know what unix 'nice' is you might want to read http://en.wikipedia.org/wiki/Nice_(Unix). TL;DR: it makes your background processes not eat all teh CPUz.