Fix spin-loop/cleanup failure mode within run loop

This ensures that exceptions raised in thread callback hooks are rescued
and properly mark jobs as failed.

Fixes #23 and #41

lib/delayed/worker.rb

@@ -98,12 +98,10 @@ def work_off(num = 100)
         pool = Concurrent::FixedThreadPool.new(jobs.length)
         jobs.each do |job|
           pool.post do
-            run_thread_callbacks(job) do
-              if run_job(job)
-                success.increment
-              else
-                failure.increment
-              end
+            if run_job(job)
+              success.increment
+            else
+              failure.increment
             end
           end
         end
@@ -122,25 +120,27 @@ def run_thread_callbacks(job, &block)
     end
 
     def run(job)
-      metadata = {
-        status: 'RUNNING',
-        name: job.name,
-        run_at: job.run_at,
-        created_at: job.created_at,
-        priority: job.priority,
-        queue: job.queue,
-        attempts: job.attempts,
-        enqueued_for: (Time.current - job.created_at).round,
-      }
-      job_say job, metadata.to_json
-      run_time = Benchmark.realtime do
-        Timeout.timeout(max_run_time(job).to_i, WorkerTimeout) do
-          job.invoke_job
+      run_thread_callbacks(job) do
+        metadata = {
+          status: 'RUNNING',
+          name: job.name,
+          run_at: job.run_at,
+          created_at: job.created_at,
+          priority: job.priority,
+          queue: job.queue,
+          attempts: job.attempts,
+          enqueued_for: (Time.current - job.created_at).round,
+        }
+        job_say job, metadata.to_json
+        run_time = Benchmark.realtime do
+          Timeout.timeout(max_run_time(job).to_i, WorkerTimeout) do
+            job.invoke_job
+          end
+          job.destroy
         end
-        job.destroy
+        job_say job, format('COMPLETED after %.4f seconds', run_time)
+        true # did work
       end
-      job_say job, format('COMPLETED after %.4f seconds', run_time)
-      true # did work
     rescue DeserializationError => e
       job_say job, "FAILED permanently with #{e.class.name}: #{e.message}", 'error'