Before I dive into my issue, I want to clarify that I've done extensive searching and could not find a specific answer to my situation. I have a Ruby on Rails application that I deploy on both Heroku and an EC2 instance. To manage background jobs, I use Sidekiq along with Sidekiq Cron for scheduling tasks. My aim is to initialize Sidekiq Cron jobs only on the EC2 instance and not on Heroku, for which I used the following condition in my configuration:
# Initialize Sidekiq Cron only if not running on Heroku
unless ENV['DYNO']
schedule_file = 'config/schedule.yml'
if File.exist?(schedule_file) && Sidekiq.server?
Sidekiq::Cron::Job.load_from_hash YAML.load_file(schedule_file)
end
end
This condition checks for the presence of the DYNO environment variable, which should theoretically exist only on Heroku, to prevent Sidekiq Cron from initializing there. However, I've encountered a situation where, despite this check, Sidekiq Cron jobs were somehow initialized on my Heroku deployment, leading to unexpected behavior and significant issues in production.
I am puzzled by this because, to my knowledge, the DYNO environment variable should be a reliable indicator of a Heroku environment. I've confirmed that the config/schedule.yml exists and is correctly formatted. Sidekiq is also functioning as expected outside of this issue.
Has anyone encountered a similar problem or can provide insight into why the DYNO environment variable check might fail in this context? Could there be a difference in how environment variables are managed or exposed in Heroku that I'm missing? Any guidance or suggestions on how to effectively isolate Sidekiq Cron initialization to only the EC2 environment would be greatly appreciated.
After a thorough investigation and a restless night, I discovered that the problem was not with the DYNO environment variable check, but with the behavior of Sidekiq Cron. Sidekiq Cron appears to automatically load the cron configuration file, which is named config/schedule.yml. This meant that, despite my conditional check, the cron jobs were still being initialized on Heroku because the file existed and followed the naming convention.
There are multiple ways to load the jobs from a YAML file
The gem will automatically load the jobs mentioned in config/schedule.yml file (it supports ERB)
To fix this, I renamed the cron configuration file from config/schedule.yml to config/ec2_schedule.yml. Then, I changed my condition to load this file only when the DYNO environment variable is not present, ensuring that the cron jobs are only initialized on the EC2 instance and not on Heroku.
# Initialize Sidekiq Cron only if not running on Heroku
unless ENV['DYNO']
schedule_file = 'config/ec2_schedule.yml'
if File.exist?(schedule_file) && Sidekiq.server?
Sidekiq::Cron::Job.load_from_hash YAML.load_file(schedule_file)
end
end