Add ENV variable to only allow Sidekiq scheduler to run on a particular host.

config/initializers/100-sidekiq.rb

@@ -15,7 +15,6 @@ Sidekiq.configure_server do |config|
 end
 
 if Sidekiq.server?
-
   # warm up AR
   RailsMultisite::ConnectionManagement.each_connection do
     (ActiveRecord::Base.connection.tables - %w[schema_migrations]).each do |table|
@@ -24,6 +23,9 @@ if Sidekiq.server?
   end
 
   Rails.application.config.after_initialize do
+    scheduler_hostname = ENV["UNICORN_SCHEDULER_HOSTNAME"]
+
+    if !scheduler_hostname || scheduler_hostname == `hostname`.strip
       require 'scheduler/scheduler'
       manager = Scheduler::Manager.new
       Scheduler::Manager.discover_schedules.each do |schedule|
@@ -41,6 +43,7 @@ if Sidekiq.server?
         end
       end
     end
+  end
 end
 
 Sidekiq.logger.level = Logger::WARN