Likely fix #2458, fix #2031 - handle out-of-order deletes for statuses (#2734)

* Likely fix #2458, fix #2031 - handle out-of-order deletes for statuses

If a delete arrives before the original status, cache that information
for 6h, and if the original status arrives in that window, ignore it

* Add test case

app/services/process_feed_service.rb

@@ -40,6 +40,11 @@ class ProcessFeedService < BaseService
     private
 
     def create_status
+      if redis.exists("delete_upon_arrival:#{id}")
+        Rails.logger.debug "Delete for status #{id} was queued, ignoring"
+        return
+      end
+
       Rails.logger.debug "Creating remote status #{id}"
       status, just_created = status_from_xml(@xml)
 
@@ -82,7 +87,13 @@ class ProcessFeedService < BaseService
     def delete_status
       Rails.logger.debug "Deleting remote status #{id}"
       status = Status.find_by(uri: id)
-      RemoveStatusService.new.call(status) unless status.nil?
+
+      if status.nil?
+        redis.setex("delete_upon_arrival:#{id}", 6 * 3_600, id)
+      else
+        RemoveStatusService.new.call(status)
+      end
+
       nil
     end
 
@@ -283,5 +294,9 @@ class ProcessFeedService < BaseService
 
       "#{username}@#{domain}"
     end
+
+    def redis
+      Redis.current
+    end
   end
 end