Crons: add sidekiq-scheduler zero config support.

- Adds support for `sidekiq-scheduler` instrumentation without any
  configuration from the user.
- Based on getsentry#2170.

sentry-sidekiq/Gemfile

@@ -24,6 +24,7 @@ sidekiq_version = Gem::Version.new(sidekiq_version)
 
 gem "sidekiq", "~> #{sidekiq_version}"
 gem "sidekiq-cron" if sidekiq_version >= Gem::Version.new("6.0")
+gem "sidekiq-scheduler" if sidekiq_version >= Gem::Version.new("6.0")
 
 gem "rails", "> 5.0.0", "< 7.1.0"
 

sentry-sidekiq/lib/sentry-sidekiq.rb

@@ -42,3 +42,4 @@ class Railtie < ::Rails::Railtie
 
 # patches
 require "sentry/sidekiq/cron/job"
+require "sentry/sidekiq/sidekiq-scheduler/scheduler"

sentry-sidekiq/lib/sentry/sidekiq/sidekiq-scheduler/scheduler.rb

@@ -0,0 +1,41 @@
+# frozen_string_literal: true
+
+return unless defined?(::SidekiqScheduler::Scheduler)
+
+module Sentry
+  module SidekiqScheduler
+    module Scheduler
+      def new_job(name, interval_type, config, schedule, options)
+        # Schedule the job upstream first
+        # SidekiqScheduler does not validate schedules
+        # It will fail with an error if the schedule in the config is invalid.
+        # If this errors out, let it fall through.
+        rufus_job = super(name, interval_type, config, schedule, options)
+
+        # Constantize the job class, and fail gracefully if it could not be found
+        klass_const =
+        begin
+          config.fetch("class").constantize
+        rescue NameError
+          return rufus_job
+        end
+
+        monitor_config = Sentry::Cron::MonitorConfig.from_crontab(schedule)
+
+        # only patch if not explicitly included in job by user
+        unless klass_const.send(:ancestors).include?(Sentry::Cron::MonitorCheckIns)
+          klass_const.send(:include, Sentry::Cron::MonitorCheckIns)
+          klass_const.send(:sentry_monitor_check_ins,
+                            slug: name,
+                            monitor_config: monitor_config)
+
+          ::Sidekiq.logger.info "Injected Sentry Crons monitor checkins into #{config.fetch("class")}"
+        end
+
+        return rufus_job
+      end
+    end
+  end
+end
+
+Sentry.register_patch(:sidekiq_scheduler, Sentry::SidekiqScheduler::Scheduler, ::SidekiqScheduler::Scheduler)

sentry-sidekiq/spec/fixtures/sidekiq-scheduler-schedule.yml

@@ -0,0 +1,9 @@
+enabled: true
+dynamic: true
+:schedule:
+  happy:
+    cron: "* * * * *"
+    class: "HappyWorkerDup"
+  manual:
+    cron: "* * * * *"
+    class: "SadWorkerWithCron"

sentry-sidekiq/spec/sentry/sidekiq/sidekiq-scheduler/scheduler_spec.rb

@@ -0,0 +1,44 @@
+require 'spec_helper'
+
+return unless defined?(SidekiqScheduler::Scheduler)
+
+RSpec.describe Sentry::SidekiqScheduler::Scheduler do
+  before do
+    perform_basic_setup { |c| c.enabled_patches += [:sidekiq_scheduler] }
+  end
+
+  before do
+    schedule_file = 'spec/fixtures/sidekiq-scheduler-schedule.yml'
+    sidekiq_config = ::Sidekiq::Config.new({scheduler: YAML.load_file(schedule_file)})
+
+    # Sidekiq::Scheduler merges it's config with Sidekiq.
+    # To grab a config for it to start, we need to pass sidekiq configuration 
+    # (defaults should be fine though).
+    scheduler_config = SidekiqScheduler::Config.new(sidekiq_config: sidekiq_config)
+
+    # Making and starting a Manager instance will load the jobs
+    schedule_manager = SidekiqScheduler::Manager.new(scheduler_config)
+    schedule_manager.start
+  end
+
+  it 'patches class' do
+    expect(SidekiqScheduler::Scheduler.ancestors).to include(described_class)
+  end
+
+  it 'patches HappyWorker' do
+    expect(HappyWorkerDup.ancestors).to include(Sentry::Cron::MonitorCheckIns)
+    expect(HappyWorkerDup.sentry_monitor_slug).to eq('happy')
+    expect(HappyWorkerDup.sentry_monitor_config).to be_a(Sentry::Cron::MonitorConfig)
+    expect(HappyWorkerDup.sentry_monitor_config.schedule).to be_a(Sentry::Cron::MonitorSchedule::Crontab)
+    expect(HappyWorkerDup.sentry_monitor_config.schedule.value).to eq('* * * * *')
+  end
+
+  it 'does not override SadWorkerWithCron manually set values' do
+    expect(SadWorkerWithCron.ancestors).to include(Sentry::Cron::MonitorCheckIns)
+    expect(SadWorkerWithCron.sentry_monitor_slug).to eq('failed_job')
+    expect(SadWorkerWithCron.sentry_monitor_config).to be_a(Sentry::Cron::MonitorConfig)
+    expect(SadWorkerWithCron.sentry_monitor_config.schedule).to be_a(Sentry::Cron::MonitorSchedule::Crontab)
+    expect(SadWorkerWithCron.sentry_monitor_config.schedule.value).to eq('5 * * * *')
+  end
+end
+

sentry-sidekiq/spec/spec_helper.rb

@@ -11,6 +11,10 @@
 require "sidekiq/embedded" if WITH_SIDEKIQ_7
 require 'sidekiq-cron' if RUBY_VERSION.to_f >= 2.7 && WITH_SIDEKIQ_6 || WITH_SIDEKIQ_7
 
+# TODO: Make this requirement optional?
+# TODO: Verify sidekiq-schedule works on Ruby 2.7
+require 'sidekiq-scheduler' if RUBY_VERSION.to_f >= 2.7 && WITH_SIDEKIQ_6 || WITH_SIDEKIQ_7
+
 require "sentry-ruby"
 
 require 'simplecov'