如何在运行具有不同 Ruby 版本的多个 Rails 应用程序的服务器上的 cron 作业中使用路径

Question

I have a server running two Ruby on Rails applications, and each of these applications runs under different Ruby versions. I am using RVM as my Ruby version manager.

Both of the applications have cron tasks scheduled and use the Whenever gem to generate the cron configuration file, shown below.

When generating the cron file, each application writes a different path, with its particular path to the Ruby executable, on cron file.

Can this cause a conflict? If so what is the best approach to correctly run the cron tasks of both projects?

# Begin Whenever generated tasks for: astego at: 2020-02-20 19:09:55 +0000
PATH=/var/www/astego/shared/bundle/ruby/2.4.0/bin:/home/deploy/.rvm/gems/ruby-2.4.2/bin:/home/deploy/.rvm/gems/ruby-2.4.2@global/bin:/home/deploy/.rvm/rubies/ruby-2.4.2/bin:/home/deploy/.rvm/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games

50 6 * * * /bin/bash -l -c 'cd /var/www/astego/releases/20200220190804 && bundle exec bin/rails runner -e production '\''User.send_birthday_message'\'''

0 4 1 * * /bin/bash -l -c 'cd /var/www/astego/releases/20200220190804 && bundle exec bin/rails runner -e production '\''User.send_last_three_months_unpaid'\'''

# End Whenever generated tasks for: astego at: 2020-02-20 19:09:55 +0000

# Begin Whenever generated tasks for: importador_atual at: 2020-02-19 21:12:31 +0000
PATH=/var/www/importador_atual/shared/bundle/ruby/2.7.0/bin:/home/deploy/.rvm/gems/ruby-2.7.0/bin:/home/deploy/.rvm/gems/ruby-2.7.0@global/bin:/home/deploy/.rvm/rubies/ruby-2.7.0/bin:/home/deploy/.rvm/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games

0 23 * * * /bin/bash -l -c 'cd /var/www/importador_atual/releases/20200219211048 && bundle exec bin/rails runner -e production '\''ImportarService.importar'\'''

# End Whenever generated tasks for: importador_atual at: 2020-02-19 21:12:31 +0000

Answer 1

A job running in a crontab is an entirely separate task, running in its own environment. It's possible to wire things up so they talk, or conflict, but general applications aren't aware of each other.

As long as your Rails applications use separate server ports and write to separate files you should be fine.

The actual tasks you're running aren't what we'd normally include in a cron script; Normally Rails is a long-running task that isn't started on a repeated schedule. Running a small scheduled application that is part of a Rails site would normally be done in a crontab using rails runner or as a Rake task. (I recommend the first but most people seem to not know it exists and use Rake.) I'd recommend researching this and decide if you're going about it the right way. rails runner makes it trivial to access the DB and all the Rails models just as in your normal Rails environment, it's just headless, which results in lighter-weight code and faster startup.