Error if self enqueue fails

CHANGELOG.md

@@ -1,3 +1,7 @@
+## Unreleased
+
+- Add re-enqueue checks [#76](https://github.com/hlascelles/que-scheduler/pull/76)
+
 ## 3.2.3 (2019-03-06)
 
 - Namespace support modules [#54](https://github.com/hlascelles/que-scheduler/pull/54)

gemfiles/activesupport_4.gemfile.lock

@@ -1,7 +1,7 @@
 PATH
   remote: ..
   specs:
-    que-scheduler (3.2.2)
+    que-scheduler (3.2.3)
       activesupport (>= 4.0)
       backports (~> 3.10)
       fugit (~> 1.1, >= 1.1.8)

gemfiles/activesupport_5.gemfile.lock

@@ -1,7 +1,7 @@
 PATH
   remote: ..
   specs:
-    que-scheduler (3.2.2)
+    que-scheduler (3.2.3)
       activesupport (>= 4.0)
       backports (~> 3.10)
       fugit (~> 1.1, >= 1.1.8)

lib/que/scheduler/scheduler_job.rb

@@ -65,11 +65,15 @@ def check_enqueued_job(enqueued_job, job_class, args, logs)
 
       def enqueue_self_again(scheduler_job_args, last_full_execution, job_dictionary, enqueued_jobs)
         next_run_at = scheduler_job_args.as_time.beginning_of_minute + SCHEDULER_FREQUENCY
-        SchedulerJob.enqueue(
+        enqueued_job = SchedulerJob.enqueue(
           last_run_time: last_full_execution.iso8601,
           job_dictionary: job_dictionary,
           run_at: next_run_at
         )
+        unless check_enqueued_job(enqueued_job, SchedulerJob, {}, [])
+          raise 'SchedulerJob could not self-schedule. Has `.enqueue` been monkey patched?'
+        end
+
         Audit.append(attrs[:job_id], scheduler_job_args.as_time, enqueued_jobs)
       end
     end

spec/que/scheduler/scheduler_job_spec.rb

@@ -53,6 +53,20 @@
         )
       end
 
+      # Some middlewares can cause an enqueue not to enqueue a job.
+      # When the main job fails to self enqueue, we must error.
+      it "errors when the enqueue call does not enqueue the #{described_class} job" do
+        described_class.enqueue
+        expect(described_class).to receive(:enqueue).and_return(false)
+        expect_any_instance_of(::Que::Job).to receive(:handle_error).once.and_call_original
+        ::Que::Job.work
+
+        # The job will have been re-enqueued, not by itself during normal operation, but by the
+        # standard que job error retry semantics.
+        hash = expect_one_itself_job
+        expect(hash['error_count']).to eq(1)
+      end
+
       def run_test(initial_job_args, to_be_scheduled)
         described_class.enqueue(initial_job_args)
         ::Que::Job.work
@@ -172,12 +186,17 @@ def expect_one_result(args, queue, priority)
     end
   end
 
-  def expect_itself_enqueued
+  def expect_one_itself_job
     itself_jobs = DbSupport.jobs_by_class(QS::SchedulerJob)
     expect(itself_jobs.count).to eq(1)
-    hash = itself_jobs.first.to_h
+    itself_jobs.first.to_h
+  end
+
+  def expect_itself_enqueued
+    hash = expect_one_itself_job
     expect(hash['queue']).to eq('')
     expect(hash['priority']).to eq(0)
+    expect(hash['error_count']).to eq(0)
     expect(hash['job_class']).to eq('Que::Scheduler::SchedulerJob')
     expect(hash['run_at']).to eq(
       run_time.beginning_of_minute + described_class::SCHEDULER_FREQUENCY