Improve default slug generation for Crons mixin

Closes #2138

CHANGELOG.md

@@ -1,5 +1,9 @@
 ## Unreleased
 
+### Features
+
+- Improve default slug generation for Crons [#2168](https://github.com/getsentry/sentry-ruby/pull/2168)
+
 ### Bug Fixes
 
 - Fixed a deprecation in `sidekiq-ruby` error handler [#2160](https://github.com/getsentry/sentry-ruby/pull/2160)

sentry-ruby/lib/sentry/cron/monitor_check_ins.rb

@@ -1,9 +1,11 @@
 module Sentry
   module Cron
     module MonitorCheckIns
+      MAX_SLUG_LENGTH = 50
+
       module Patch
         def perform(*args)
-          slug = self.class.sentry_monitor_slug || self.class.name
+          slug = self.class.sentry_monitor_slug
           monitor_config = self.class.sentry_monitor_config
 
           check_in_id = Sentry.capture_check_in(slug,
@@ -43,7 +45,10 @@ def sentry_monitor_check_ins(slug: nil, monitor_config: nil)
         end
 
         def sentry_monitor_slug
-          @sentry_monitor_slug
+          @sentry_monitor_slug ||= begin
+            slug = name.gsub('::', '-').downcase
+            slug[-MAX_SLUG_LENGTH..] || slug
+          end
         end
 
         def sentry_monitor_config

sentry-ruby/spec/sentry/cron/monitor_check_ins_spec.rb

@@ -104,13 +104,13 @@ def perform(a, b = 42, c: 99)
 
       it 'calls capture_check_in twice' do
         expect(Sentry).to receive(:capture_check_in).with(
-          'Job',
+          'job',
           :in_progress,
           hash_including(monitor_config: nil)
         ).ordered.and_call_original
 
         expect(Sentry).to receive(:capture_check_in).with(
-          'Job',
+          'job',
           :ok,
           hash_including(:check_in_id, monitor_config: nil, duration: 0)
         ).ordered.and_call_original
@@ -119,6 +119,31 @@ def perform(a, b = 42, c: 99)
       end
     end
 
+    context 'with very long class name' do
+      before do
+        mod = described_class
+
+        job_class = Class.new do
+          include mod
+
+          sentry_monitor_check_ins
+
+          def work(a, b, c); end
+
+          def perform(a, b = 42, c: 99)
+            work(a, b, c)
+          end
+        end
+
+        stub_const('VeryLongOuterModule::VeryVeryVeryVeryLongInnerModule::Job', job_class)
+      end
+
+      it 'truncates from the beginning and parameterizes slug' do
+        slug = VeryLongOuterModule::VeryVeryVeryVeryLongInnerModule::Job.sentry_monitor_slug
+        expect(slug).to eq('ongoutermodule-veryveryveryverylonginnermodule-job')
+      end
+    end
+
     context 'patched with custom options' do
       let(:config) { Sentry::Cron::MonitorConfig::from_interval(1, :minute) }