How to set rankings (and reputation in general) using a background job?

Background job for calculating rankings

Rank rules can be run in the background, for instance running a small rake task as part of a cron job. Create a file lib/tasks/cron.rake like:

task :daily_cron_job => :environment do
  Merit::RankRules.new.check_rank_rules
end

Then run rake daily_cron_job as part of a daily cron job (or hourly,however you need), and it will compute rankings regularly.

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Or you can use Crono Gem, which would simplify this process. You can add this rule to an active job and run using Crono like so:

app/jobs/check_merit_rules_job.rb

class CheckMeritRankRulesJob < ActiveJob::Base
  def perform
    ActiveRecord::Base.connection_pool.with_connection do
     Merit::RankRules.new.check_rank_rules
    end
  end
end

config/cronotab.rb

Crono.perform(CheckMeritRankRulesJob).every 5.minutes #configure time

Note: If you are using Crono make sure the ActiveJob perform block doesn't take any arguments.(Merit doesn't need arguments anyway)

The rankings are ran on the a whole database scope and not only on some entries, and because they tend to need more information/computing that would take too long to compute as part of an HTTP request.

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Background job for awarding Badges/Point

If you configure merit to not check badge/point rules on each request (checks_on_each_request) you'll need to check them in the background. The configuration for this is available in merit initializer file config/initializers/merit.rb

Behind the scenes, merit uses an after_filter on every meritable controller action and logs it into merit_actions table which makes it flexible to process Badge/Point rules later. You can read related code here L10

The call for checking unprocessed jobs is:

Merit::Action.check_unprocessed

Therefore, it makes it very flexible to run merit rules through a background job. Here is how you can configure Merit to use a background job (Same as rankings)

app/jobs/check_unprocessed_merit_rules_job.rb

class CheckUnprocessedMeritRulesJob < ActiveJob::Base
  def perform
    ActiveRecord::Base.connection_pool.with_connection do
     Merit::Action.check_unprocessed
    end
  end
end

config/cronotab.rb

Crono.perform(CheckUnprocessedMeritRulesJob).every 5.minutes #configure time as it fits your app needs

A little tip on performance: Use redis sorted sets to store points and rankings for each user and whenever ranking/points updates after computation use redis pub/sub to push updates in realtime without compromising performance.