Make pipeline schedule worker resilient

Currently, pipeline schedule worker is unstable because it's
sometimes killed by excessive memory consumption.
In order to improve the performance, we add the following fixes:

1. next_run_at is always real_next_run, which means the value
   always takes into account of worker's cron schedule
1. Remove exlusive lock. This is already covered by real_next_run
   change.
1. Use RunPipelineScheduleWorker for avoiding memory killer.
   Memory consumption is spread to the multiple sidekiq worker.

2 files changed, 28 insertions, 39 deletions

diff --git a/app/workers/pipeline_schedule_worker.rb b/app/workers/pipeline_schedule_worker.rb
index 8a9ee7808e4..9410fd1a786 100644
--- a/app/workers/pipeline_schedule_worker.rb
+++ b/app/workers/pipeline_schedule_worker.rb
@@ -3,47 +3,12 @@
 class PipelineScheduleWorker
   include ApplicationWorker
   include CronjobQueue
-  include ::Gitlab::ExclusiveLeaseHelpers
 
-  EXCLUSIVE_LOCK_KEY = 'pipeline_schedules:run:lock'
-  LOCK_TIMEOUT = 50.minutes
-
-  # rubocop: disable CodeReuse/ActiveRecord
   def perform
-    in_lock(EXCLUSIVE_LOCK_KEY, ttl: LOCK_TIMEOUT, retries: 1) do
-      Ci::PipelineSchedule.active.where("next_run_at < ?", Time.now)
-        .preload(:owner, :project).find_each do |schedule|
-
-        schedule.schedule_next_run!
-
-        Ci::CreatePipelineService.new(schedule.project,
-                                      schedule.owner,
-                                      ref: schedule.ref)
-          .execute!(:schedule, ignore_skip_ci: true, save_on_errors: true, schedule: schedule)
-      rescue => e
-        error(schedule, e)
+    Ci::PipelineSchedule.runnable_schedules.preloaded.find_in_batches do |schedules|
+      schedules.each do |schedule|
+        Ci::PipelineScheduleService.new(schedule.project, schedule.owner).execute(schedule)
       end
     end
   end
-  # rubocop: enable CodeReuse/ActiveRecord
-
-  private
-
-  def error(schedule, error)
-    failed_creation_counter.increment
-
-    Rails.logger.error "Failed to create a scheduled pipeline. " \
-                       "schedule_id: #{schedule.id} message: #{error.message}"
-
-    Gitlab::Sentry
-      .track_exception(error,
-                       issue_url: 'https://gitlab.com/gitlab-org/gitlab-ce/issues/41231',
-                       extra: { schedule_id: schedule.id })
-  end
-
-  def failed_creation_counter
-    @failed_creation_counter ||=
-      Gitlab::Metrics.counter(:pipeline_schedule_creation_failed_total,
-                              "Counter of failed attempts of pipeline schedule creation")
-  end
 end
diff --git a/app/workers/run_pipeline_schedule_worker.rb b/app/workers/run_pipeline_schedule_worker.rb
index f72331c003a..43e0b9db22f 100644
--- a/app/workers/run_pipeline_schedule_worker.rb
+++ b/app/workers/run_pipeline_schedule_worker.rb
@@ -21,6 +21,30 @@ class RunPipelineScheduleWorker
     Ci::CreatePipelineService.new(schedule.project,
                                   user,
                                   ref: schedule.ref)
-      .execute(:schedule, ignore_skip_ci: true, save_on_errors: false, schedule: schedule)
+      .execute!(:schedule, ignore_skip_ci: true, save_on_errors: false, schedule: schedule)
+  rescue Ci::CreatePipelineService::CreateError
+    # no-op. This is a user operation error such as corrupted .gitlab-ci.yml.
+  rescue => e
+    error(schedule, e)
+  end
+
+  private
+
+  def error(schedule, error)
+    failed_creation_counter.increment
+
+    Rails.logger.error "Failed to create a scheduled pipeline. " \
+                       "schedule_id: #{schedule.id} message: #{error.message}"
+
+    Gitlab::Sentry
+      .track_exception(error,
+                       issue_url: 'https://gitlab.com/gitlab-org/gitlab-ce/issues/41231',
+                       extra: { schedule_id: schedule.id })
+  end
+
+  def failed_creation_counter
+    @failed_creation_counter ||=
+      Gitlab::Metrics.counter(:pipeline_schedule_creation_failed_total,
+                              "Counter of failed attempts of pipeline schedule creation")
   end
 end