Maintenance: Reduce logging (disable info) of ActiveJob.

app/jobs/application_job.rb

@@ -1,6 +1,7 @@
 class ApplicationJob < ActiveJob::Base
   include ApplicationJob::HasDelayedJobMonitoringCompatibilty
   include ApplicationJob::HasQueuingPriority
+  include ApplicationJob::HasCustomLogging
 
   # Automatically retry jobs that encountered a deadlock
   # retry_on ActiveRecord::Deadlocked

app/jobs/application_job/has_custom_logging.rb

@@ -0,0 +1,46 @@
+class ApplicationJob
+  module HasCustomLogging
+    extend ActiveSupport::Concern
+
+    # ActiveJob default logging is to verbose in default setups.
+    # Therefore we overwrite the default `ActiveJob::Logging::LogSubscriber` with a custom version.
+    # This is currently done in an initializer because Rails 5.2 does not support detaching subscribers.
+    # The custom version comes with two changes:
+    # - Don't log info level lines
+    # - Log (info) that an ActiveJob was not enqueued in case there is already one queued with the same ActiveJobLock
+    class LogSubscriber < ActiveJob::Logging::LogSubscriber
+
+      # ATTENTION: Uncomment this line to enable info logging again
+      def info(*); end
+
+      def enqueue(event)
+        super if job_enqueued?(event)
+      end
+
+      def enqueue_at(event)
+        super if job_enqueued?(event)
+      end
+
+      private
+
+      def job_enqueued?(event)
+        job = event.payload[:job]
+
+        # having a provider_job_id means that the job was enqueued
+        return true if job.provider_job_id.present?
+
+        # we're only interested to log not enqueued lock-jobs for now
+        return false if !job.is_a?(HasActiveJobLock)
+
+        info do
+          "Won't enqueue #{job.class.name} (Job ID: #{job.job_id}) to #{queue_name(event)}" + args_info(job) + " because of already existing Job with Lock Key '#{job.lock_key}'."
+        end
+
+        # don't log regular enqueue log lines
+        false
+      end
+    end
+  end
+end
+
+ApplicationJob::HasCustomLogging::LogSubscriber.attach_to :active_job

app/jobs/concerns/has_active_job_lock.rb

@@ -120,7 +120,6 @@ module HasActiveJobLock
   end
 
   def existing_active_job_lock!
-    logger.info "Won't enqueue #{self.class.name} (Job ID: #{job_id}) because of already existing job with lock key '#{lock_key}'."
     throw :abort
   end
 end

config/initializers/workaround_active_job_logging.rb

@@ -0,0 +1,18 @@
+# This is a workaround because `ActiveSupport::Subscriber` supports only `attach_to` but not `detach_from` in Rails 5.2.
+# `detach_from` was added with Rails 6.0: https://github.com/rails/rails/commit/ca19b7f5d86aa590077766cbe8006f952b6d4296
+# Once Rails 6.0 is used `ActiveJob::Logging::LogSubscriber.detach_from :active_job` needs to be added to `app/jobs/application_job.rb` instead.
+ActiveSupport.on_load(:active_job) do
+
+  # gather all `ActiveJob::Logging::LogSubscriber` event subscribers
+  subscribers = ActiveSupport::Notifications.notifier.instance_variable_get(:@subscribers).select do |subscriber|
+    subscriber.instance_variable_get(:@delegate).instance_of?(ActiveJob::Logging::LogSubscriber)
+  end
+
+  # remove gathered event subscribers in a dedicated step to not work on iterating array
+  subscribers.each do |subscriber|
+    ActiveSupport::Notifications.notifier.unsubscribe(subscriber)
+  end
+
+  # remove whole `ActiveJob::Logging::LogSubscriber` subscriber reference
+  ActiveSupport::Subscriber.subscribers.delete_if { |subscriber| subscriber.instance_of?(ActiveJob::Logging::LogSubscriber) }
+end