prevent serializing TII client (procs)

fixes FOO-1230
flag=none

TEST PLAN:
  1) new up a processor
  2) access it's client (set the ivar for
     tii)
  3) call "#resubmit" with a submission and asset
     string
  4) serialized object should not have the TII client
     inside it.

Change-Id: I99257986f730838b6bda2254fec11edad935ea61
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/253573
Reviewed-by: Cody Cutrer <cody@instructure.com>
Product-Review: Cody Cutrer <cody@instructure.com>
Tested-by: Service Cloud Jenkins <svc.cloudjenkins@instructure.com>
QA-Review: Ethan Vizitei <evizitei@instructure.com>

lib/turnitin/outcome_response_processor.rb

@@ -62,18 +62,22 @@ module Turnitin
       # exponential backoff. We should add
       # one to give TII more time to process
       # attachments.
-      delay(max_attempts: self.class.max_attempts).update_originality_data(submission, asset_string)
+      stash_turnitin_client do
+        delay(max_attempts: self.class.max_attempts).update_originality_data(submission, asset_string)
+      end
     rescue Errors::ScoreStillPendingError
       if attempt_number == self.class.max_attempts
         create_error_attachment
         raise
       else
         turnitin_processor = Turnitin::OutcomeResponseProcessor.new(@tool, @assignment, @user, @outcomes_response_json)
-        turnitin_processor.delay(max_attempts: Turnitin::OutcomeResponseProcessor.max_attempts,
-          priority: Delayed::LOW_PRIORITY,
-          attempts: attempt_number,
-          run_at: Time.now.utc + (attempt_number ** 4) + 5).
-          process
+        stash_turnitin_client do
+          turnitin_processor.delay(max_attempts: Turnitin::OutcomeResponseProcessor.max_attempts,
+            priority: Delayed::LOW_PRIORITY,
+            attempts: attempt_number,
+            run_at: Time.now.utc + (attempt_number ** 4) + 5).
+            process
+        end
       end
     rescue StandardError
       if attempt_number == self.class.max_attempts
@@ -83,7 +87,9 @@ module Turnitin
     end
 
     def resubmit(submission, asset_string)
-      delay(max_attempts: self.class.max_attempts).update_originality_data(submission, asset_string)
+      stash_turnitin_client do
+        delay(max_attempts: self.class.max_attempts).update_originality_data(submission, asset_string)
+      end
     end
 
     def turnitin_client
@@ -112,11 +118,6 @@ module Turnitin
       end
     end
 
-    # dont try and recreate the turnitin client in a delayed job. bad things happen
-    def delay(**)
-      stash_turnitin_client { super }
-    end
-
     private
 
     def create_error_attachment
@@ -128,6 +129,13 @@ module Turnitin
       )
     end
 
+    # the turnitin client has a proc embedded
+    # in it's faraday connection.  If you try to serialize it,
+    # it will fail to deserialize (for good reason, closures can't
+    # take the whole state of the system with them when written
+    # as yaml).  This method un-sets the ivar long enough to
+    # serialize the object for job processing (a turnitin client
+    # will be created in the job when necessary).
     def stash_turnitin_client
       old_turnit_client = @_turnitin_client
       @_turnitin_client = nil

spec/lib/turnitin/outcome_response_processor_spec.rb

@@ -171,5 +171,15 @@ module Turnitin
         expect(submission.turnitin_data[attachment.asset_string][:public_error_message]).to start_with "Turnitin has not"
       end
     end
+
+    describe "#resubmit" do
+      it "doesn't serialize the whole TII client" do
+        expect(subject.turnitin_client).to_not be_nil
+        submission = Submission.new(id: 1)
+        output_job = subject.resubmit(submission, "asset_string")
+        output_job = Delayed::Job.where(tag: "Turnitin::OutcomeResponseProcessor#update_originality_data").last
+        expect(output_job.handler).to_not include("ruby/object:Turnitin::TiiClient")
+      end
+    end
   end
 end