Improve error logging for message batch dispatching

closes VICE-2941
flag=none

Test Plan:
 - tests pass
 - verify post merge in failed job error stack

Change-Id: I0b1913e78fb5791ce6bb76b56e0095683c4466a2
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/293899
Tested-by: Service Cloud Jenkins <[email protected]>
Reviewed-by: Chawn Neal <[email protected]>
Product-Review: Chawn Neal <[email protected]>
QA-Review: Caleb Guanzon <[email protected]>

lib/message_dispatcher.rb

@@ -19,6 +19,9 @@
 #
 
 class MessageDispatcher < Delayed::PerformableMethod
+  class MessagesInBatchNotFound < StandardError
+  end
+
   DeliverWorker = Struct.new(:message) do
     def perform
       message.for_queue.deliver
@@ -88,12 +91,13 @@ def self.deliver_batch(messages)
         message_ids << m.id
         previous_time = m.created_at
       end
-      raise ActiveRecord::RecordNotFound unless messages.length == queued.length
+      raise MessagesInBatchNotFound, "IDs not found: #{queued.map(&:id) - messages.map(&:id)}" unless messages.length == queued.length
     end
     messages.each do |message|
       message.deliver
     rescue
       # this delivery failed, we'll have to make an individual job to retry
+
       dispatch(message)
     end
   end

spec/lib/message_dispatcher_spec.rb

@@ -60,6 +60,17 @@
       @messages = (0...3).map { message_model(dispatch_at: Time.now, workflow_state: "staged", to: "somebody", updated_at: Time.now.utc - 11.minutes, user: user_factory, path_type: "email") }
     end
 
+    it "shows message ids not found in batch process" do
+      messages = @messages
+      messages.push(Message.new(id: -1, created_at: Time.zone.now))
+      track_jobs { MessageDispatcher.batch_dispatch(messages) }
+      expect(created_jobs.size).to eq 1
+      job = created_jobs.first
+      run_jobs
+      job.reload
+      expect(job.last_error).to include("IDs not found: [-1]")
+    end
+
     it "reschedules on Mailer delivery error, but not on canceled Message" do
       track_jobs { MessageDispatcher.batch_dispatch(@messages) }
       expect(created_jobs.size).to eq 1