![]() ![]() ![]() Sidekiq_options queue: :cron, unique_for: 30.minutesīenefits of using Sidekiq Scheduler vs OS based cron jobs The scheduled tasks are standard Sidekiq workers: class ActiveMailingsWorker We have an option to change it if we need to. Per that config example, we specify a run of ActiveMailingsWorker every 10 seconds and a run of ScheduledMailingsWorker every minute.īy default, when no timezone is set with the cron string, it uses the Rails’ configured timezone in config/application.rb. Rufus Scheduler allows for seconds precision with an optional cron expression format consisting of a six fields time specifier where the first one is for the seconds. Sidekiq Scheduler config looks like this: # config/sidekiq_scheduler.yml Because its job is only to enqueue Sidekiq jobs and Sidekiq workers will do the actual execution, we can decrease the max_work_threads to 1.ĬonfigParser.parse is a small utility function that converts the YAML config to a hash: require 'yaml' ![]() Rufus Scheduler starts 28 threads by default. Sidekiq.schedule = ConfigParser.parse(File.join(Rails.root, "config/sidekiq_scheduler.yml"), Rails.env) In an initializer, we require sidekiq-scheduler and its UI component and configure the Sidekiq server: # config/initializers/sidekiq.rb We have a custom config for Sidekiq Scheduler that allows for more control over sharing configs between environments. The increased load to Redis when every single process tries to get a lock is acceptable for us because Redis capacity allows for that. That covers the uniqueness goal and also guarantees that no duplicate cron jobs run at the same time until the cron job finishes with success.Įach Sidekiq process running Sidekiq Scheduler will first try to register the cron job to get a lock and only then enqueue it. Although, we exclusively use the cron type of schedules, we still couple the cron jobs in Sidekiq Scheduler with using a Sidekiq plugin for unique jobs. Running Sidekiq Scheduler on multiple hosts could have some issues. By starting Sidekiq Scheduler in all Sidekiq processes distributed on all hosts we get a distibuted cron solution that resolves the single point of failure issue. Sidekiq Scheduler extends Sidekiq by starting a Rufus Scheduler thread in the same process, loading and maintaining the schedules for it. It uses Rufus Scheduler under the hood, that is itself an in-memory scheduler. Sidekiq Scheduler is a lightweight job scheduling extension for Sidekiq. Let’s first start with a brief introduction to how Sidekiq Scheduler works and then we will discuss its benefits over OS based cron jobs and look at some of the alternatives. With experimental canary deploys, human error is possible too, that could result in deploying the crons or the runner process to more than one server. ![]() If a cron job needs to run frequently and it has a long processing time, there is nothing to prevent an overlap with the next cron schedule. In case of an issue like a network or out of memory incident, we risk having a partial failure in how the service operates. The crons and the runner procesess are each deployed to a specific server respectively. There are two main problems with this setup that we want to resolve: What are the main problems with this setup? Besides deploying the Sidekiq processes, it deploys cron jobs to a specific worker server and depending on the application it might deploy other stand-alone runner processes to specific worker servers. The web servers deploy is consistent and all running processes are Phusion Passenger instances. With our standard Capistrano deploys, we deploy an application to web servers that handle web requests and to worker servers that process background jobs. We landed on a strategy for deploying cron jobs that works well for us in both scenarios. We deploy our legacy applications with Capistrano while we work on migrating them to the public cloud. We build our new microservices with the public cloud in mind and deploy them on Kubernetes. We maintain some legacy Ruby on Rails applications along with new Ruby on Rails microservices. We will discuss the motivation for migrating from OS based cron to distributed cron using Sidekiq Scheduler and the benefits we get from it. One such plugin that helped us run distributed cron, reduce maintenance costs and simplify our deployments is Sidekiq Scheduler. It has a nice ecosystem that allows extending its functionality with plugins. Sidekiq is a Ruby background jobs processing library that uses Redis for storage and is widely used in Ruby on Rails applications. ![]()
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