Cron rake task not ending after finish work - ruby-on-rails

Question

I have configured rake tasks using whenever gem to run every 5 minute. that rake task take 10 seconds to run in local but in server, It's not ending always it's stay in process list
ps -ef | grep some_rake_task`
shows like following output:
user 22628 22626 0 09:00 ? 00:00:00 /bin/sh -c /bin/bash -l -c 'cd app_direc && rake some_rake_task'
user 22630 22628 0 09:00 ? 00:00:00 /bin/bash -l -c cd app_direc && rake some_rake_task
user 22933 22630 0 09:00 ? 00:00:00 rake some_rake_task
user 22934 22933 0 09:00 ? 00:00:04 ruby /opt/user/app/shared/bundle/ruby/2.1.0/bin/rake some_rake_task
user 25261 25260 0 08:00 ? 00:00:00 /bin/sh -c /bin/bash -l -c 'cd app_direc && rake some_rake_task'
user 25263 25261 0 08:00 ? 00:00:00 /bin/bash -l -c cd app_direc && rake some_rake_task
user 25570 25263 0 08:00 ? 00:00:00 rake some_rake_task
user 25571 25570 0 08:00 ? 00:00:04 ruby /opt/user/app/shared/bundle/ruby/2.1.0/bin/rake some_rake_task
user 26570 26569 0 07:00 ? 00:00:00 /bin/sh -c /bin/bash -l -c 'cd app_direc && rake some_rake_task'
user 26573 26570 0 07:00 ? 00:00:00 /bin/bash -l -c cd app_direc && rake some_rake_task
user 26879 26573 0 07:00 ? 00:00:00 rake some_rake_task
user 26880 26879 0 07:00 ? 00:00:04 ruby /opt/user/app/shared/bundle/ruby/2.1.0/bin/rake some_rake_task
user 30915 30691 0 09:16 pts/2 00:00:00 grep --color=auto some_rake_task
I tried to kill process manually but every task initiated by crontab it's stays alive not ending. Any suggestionsm please?
My rake task code
namespace :some_rake_task do
desc "Send the email with content"
task :send => :environment do
User.find_in_batches do |user|
SendMailer.newsletter_email(user).deliver
end
end
end
But there is only below 1000 users

Answer 1

Crond detaches child processes, so when you kill crond process, spawned tasks will continue their work.
Judging by the output of ps -ef, there is no <defunct> near rake task processes, so i can decide that they are alive and running.
Your rake tasks either enter endless loop or just take much more time than you expect. In case of second it can be caused by slow network connection, for example if you call some external API service, poorly optimized SQL query or algorithm, too large database, something like that.
Advice: Try to fix your rake task or crontab entry, in order to not run rake task if same one is already running.