feat(jobs): introduce Prism and Jobs

lib/prism/jobs/worker.rb

@@ -0,0 +1,47 @@
+module Prism
+  module Jobs
+    # Pulls jobs off a Queue and performs them until none are ready.
+    # Errors raised by a job's #perform are caught and handed to the queue's
+    # retry/dead-letter bookkeeping rather than crashing the worker loop.
+    class Worker
+      def initialize(queue, queue_name: nil, error_handler: nil)
+        @queue = queue
+        @queue_name = queue_name
+        @error_handler = error_handler
+      end
+
+      # Drains every currently-ready job (does not wait for scheduled ones
+      # whose run_at is still in the future). Returns how many were processed.
+      def work_off
+        processed = 0
+        while (job = @queue.claim_next!(queue_name: @queue_name))
+          process(job)
+          processed += 1
+        end
+        processed
+      end
+
+      def process(job)
+        Instrumentation.instrument('perform_job.prism', job_class: job[:job_class],
+                                                          job_id: job[:id],
+                                                          queue_name: @queue_name) do |payload|
+          job_class = resolve_job_class(job[:job_class])
+          job_class.new.perform(*job[:args])
+          @queue.mark_completed(job[:id])
+          payload[:status] = 'completed'
+        end
+        true
+      rescue StandardError => e
+        @error_handler&.call(e, job)
+        @queue.mark_failed(job[:id], e)
+        false
+      end
+
+      private
+
+      def resolve_job_class(name)
+        Object.const_get(name)
+      end
+    end
+  end
+end