Resolve race condition during applicability generation

Race condition was possible when applicability generation was running
in parallel for the same consumer profiles.

closes #2874
https://pulp.plan.io/issues/2874

server/pulp/server/managers/consumer/applicability.py

@@ -7,6 +7,7 @@
 from uuid import uuid4
 
 from celery import task
+from pymongo.errors import DuplicateKeyError
 
 from pulp.plugins.conduits.profiler import ProfilerConduit
 from pulp.plugins.config import PluginCallConfiguration
@@ -260,16 +261,20 @@ def regenerate_applicability(profile_hash, content_type, profile_id,
                 _logger.debug(msg)
                 return
 
-            if existing_applicability:
-                # Update existing applicability object
-                existing_applicability.applicability = applicability
-                existing_applicability.save()
-            else:
+            try:
                 # Create a new RepoProfileApplicability object and save it in the db
                 RepoProfileApplicability.objects.create(profile_hash,
                                                         bound_repo_id,
-                                                        unit_profile['profile'],
+                                                        profile,
                                                         applicability)
+            except DuplicateKeyError:
+                # Update existing applicability
+                if not existing_applicability:
+                    applicability_dict = RepoProfileApplicability.get_collection().find_one(
+                        {'repo_id': bound_repo_id, 'profile_hash': profile_hash})
+                    existing_applicability = RepoProfileApplicability(**applicability_dict)
+                existing_applicability.applicability = applicability
+                existing_applicability.save()
 
     @staticmethod
     def _get_existing_repo_content_types(repo_id):
@@ -456,6 +461,8 @@ def remove_orphans():
         # Remove all RepoProfileApplicability objects that reference these profile hashes
         if missing_profile_hashes:
             rpa_collection.remove({'profile_hash': {'$in': missing_profile_hashes}})
+
+
 # Instantiate one of the managers on the object it manages for convenience
 RepoProfileApplicability.objects = RepoProfileApplicabilityManager()