Set job execution thread priority to -3 when in async mode

lib/good_job/adapter.rb

@@ -216,6 +216,7 @@ def start_async
       return unless execute_async?
 
       @capsule.start
+      @capsule.lower_thread_priority = true if GoodJob.configuration.lower_thread_priority.in?([true, nil])
       @_async_started = true
     end
 

lib/good_job/capsule.rb

@@ -24,6 +24,7 @@ def initialize(configuration: nil)
 
       @shared_executor = GoodJob::SharedExecutor.new
       @tracker = GoodJob::CapsuleTracker.new(executor: @shared_executor)
+      @lower_thread_priority = nil
 
       self.class.instances << self
     end
@@ -38,7 +39,9 @@ def start(force: false)
 
         @notifier = GoodJob::Notifier.new(enable_listening: configuration.enable_listen_notify, capsule: self, executor: @shared_executor)
         @poller = GoodJob::Poller.new(poll_interval: configuration.poll_interval)
-        @multi_scheduler = GoodJob::MultiScheduler.from_configuration(configuration, capsule: self, warm_cache_on_initialize: true)
+        @multi_scheduler = GoodJob::MultiScheduler.from_configuration(configuration, capsule: self, warm_cache_on_initialize: true).tap do |multischeduler|
+          multischeduler.lower_thread_priority = @lower_thread_priority unless @lower_thread_priority.nil?
+        end
         @notifier.recipients.push([@multi_scheduler, :create_thread])
         @poller.recipients.push(-> { @multi_scheduler.create_thread({ fanout: true }) })
 
@@ -110,6 +113,11 @@ def process_id
       @tracker.process_id
     end
 
+    def lower_thread_priority=(value)
+      @lower_thread_priority = value
+      @multi_scheduler&.lower_thread_priority = value
+    end
+
     private
 
     def configuration

lib/good_job/configuration.rb

@@ -383,6 +383,14 @@ def in_webserver?
       end || false
     end
 
+    def lower_thread_priority
+      return options[:lower_thread_priority] unless options[:lower_thread_priority].nil?
+      return rails_config[:lower_thread_priority] unless rails_config[:lower_thread_priority].nil?
+      return ActiveModel::Type::Boolean.new.cast(env['GOOD_JOB_LOWER_THREAD_PRIORITY']) unless env['GOOD_JOB_LOWER_THREAD_PRIORITY'].nil?
+
+      nil
+    end
+
     # Whether to take an advisory lock on the process record in the notifier reactor.
     # @return [Boolean]
     def advisory_lock_heartbeat

lib/good_job/multi_scheduler.rb

@@ -19,7 +19,8 @@ def self.from_configuration(configuration, capsule: GoodJob.capsule, warm_cache_
           max_cache: configuration.max_cache,
           warm_cache_on_initialize: warm_cache_on_initialize,
           cleanup_interval_seconds: configuration.cleanup_interval_seconds,
-          cleanup_interval_jobs: configuration.cleanup_interval_jobs
+          cleanup_interval_jobs: configuration.cleanup_interval_jobs,
+          lower_thread_priority: configuration.lower_thread_priority
         )
       end
 
@@ -85,6 +86,12 @@ def create_thread(state = nil)
       end
     end
 
+    def lower_thread_priority=(value)
+      schedulers.each do |scheduler|
+        scheduler.lower_thread_priority = value
+      end
+    end
+
     def stats
       scheduler_stats = schedulers.map(&:stats)
 

lib/good_job/scheduler.rb

@@ -29,6 +29,9 @@ class Scheduler
       fallback_policy: :discard,
     }.freeze
 
+    # In CRuby, this sets the thread quantum to ~12.5ms ( 100ms * 2^(-3) ).
+    LOW_THREAD_PRIORITY = -3
+
     # @!attribute [r] instances
     #   @!scope class
     #   List of all instantiated Schedulers in the current process.
@@ -39,13 +42,18 @@ class Scheduler
     # @return [String]
     attr_reader :name
 
+    # Whether to lower the thread priority to a fixed value
+    # @return [Boolean]
+    attr_accessor :lower_thread_priority
+
     # @param performer [GoodJob::JobPerformer]
     # @param max_threads [Numeric, nil] number of seconds between polls for jobs
     # @param max_cache [Numeric, nil] maximum number of scheduled jobs to cache in memory
     # @param warm_cache_on_initialize [Boolean] whether to warm the cache immediately, or manually by calling +warm_cache+
     # @param cleanup_interval_seconds [Numeric, nil] number of seconds between cleaning up job records
     # @param cleanup_interval_jobs [Numeric, nil] number of executed jobs between cleaning up job records
-    def initialize(performer, max_threads: nil, max_cache: nil, warm_cache_on_initialize: false, cleanup_interval_seconds: nil, cleanup_interval_jobs: nil)
+    # @param lower_thread_priority [Boolean] whether to lower the thread priority of execution threads
+    def initialize(performer, max_threads: nil, max_cache: nil, warm_cache_on_initialize: false, cleanup_interval_seconds: nil, cleanup_interval_jobs: nil, lower_thread_priority: false)
       raise ArgumentError, "Performer argument must implement #next" unless performer.respond_to?(:next)
 
       @performer = performer
@@ -62,6 +70,8 @@ def initialize(performer, max_threads: nil, max_cache: nil, warm_cache_on_initia
       @cleanup_tracker = CleanupTracker.new(cleanup_interval_seconds: cleanup_interval_seconds, cleanup_interval_jobs: cleanup_interval_jobs)
       @executor_options[:name] = name
 
+      self.lower_thread_priority = lower_thread_priority
+
       create_executor
       warm_cache if warm_cache_on_initialize
       self.class.instances << self
@@ -271,6 +281,7 @@ def create_task(delay = 0, fanout: false)
       future = Concurrent::ScheduledTask.new(delay, args: [self, performer], executor: executor, timer_set: timer_set) do |thr_scheduler, thr_performer|
         Thread.current.name = Thread.current.name.sub("-worker-", "-thread-") if Thread.current.name
         Thread.current[:good_job_scheduler] = thr_scheduler
+        Thread.current.priority = -3 if thr_scheduler.lower_thread_priority
 
         Rails.application.reloader.wrap do
           thr_performer.next do |found|

spec/lib/good_job/adapter_spec.rb

@@ -88,7 +88,7 @@ def perform(succeed: true)
         allow(GoodJob::Job).to receive(:enqueue).and_return(good_job)
         allow(GoodJob::Notifier).to receive(:notify)
 
-        capsule = instance_double(GoodJob::Capsule, start: nil, create_thread: nil)
+        capsule = instance_double(GoodJob::Capsule, start: nil, create_thread: nil, "lower_thread_priority=": nil)
         allow(GoodJob).to receive(:capsule).and_return(capsule)
         allow(capsule).to receive(:start)
 
@@ -99,6 +99,16 @@ def perform(succeed: true)
         expect(capsule).to have_received(:create_thread)
         expect(GoodJob::Notifier).to have_received(:notify).with({ queue_name: 'default' })
       end
+
+      it 'lowers the thread priority of the capsule' do
+        capsule = instance_double(GoodJob::Capsule, start: nil, create_thread: nil, "lower_thread_priority=": nil)
+        allow(GoodJob).to receive(:capsule).and_return(capsule)
+        allow(capsule).to receive(:start)
+
+        described_class.new(execution_mode: :async_all)
+
+        expect(capsule).to have_received(:lower_thread_priority=).with(true)
+      end
     end
   end