Only track contributions if table is available.

This is due to the problem that the callback can be called while running
an earlier database schema version (for example during earlier
migrations). We work around this by checking the current schema version
and only track contributions if the table is available.

app/models/event.rb

@@ -392,6 +392,9 @@ class Event < ActiveRecord::Base
   end
 
   def track_user_contributed_projects
-    UserContributedProjects.track(self)
+    # Note the call to .available? is due to earlier migrations
+    # that would otherwise conflict with the call to .track
+    # (because the table does not exist yet).
+    UserContributedProjects.track(self) if UserContributedProjects.available?
   end
 end

app/models/user_contributed_projects.rb

@@ -7,6 +7,9 @@ class UserContributedProjects < ActiveRecord::Base
 
   CACHE_EXPIRY_TIME = 1.day
 
+  # Schema version required for this model
+  REQUIRED_SCHEMA_VERSION = 20180223120443
+
   class << self
     def track(event)
       # For events without a project, we simply don't care.
@@ -35,6 +38,11 @@ class UserContributedProjects < ActiveRecord::Base
       end
     end
 
+    # Check if we can safely call .track (table exists)
+    def available?
+      @available_flag ||= ActiveRecord::Migrator.current_version >= REQUIRED_SCHEMA_VERSION # rubocop:disable Gitlab/PredicateMemoization
+    end
+
     private
 
     def cached_exists?(project_id:, user_id:, &block)

spec/models/event_spec.rb

@@ -51,11 +51,19 @@ describe Event do
     end
 
     describe 'after_create :track_user_contributed_projects' do
+      let(:event) { build(:push_event, project: project, author: project.owner) }
+
       it 'passes event to UserContributedProjects.track' do
-        event = build(:push_event, project: project, author: project.owner)
+        expect(UserContributedProjects).to receive(:available?).and_return(true)
         expect(UserContributedProjects).to receive(:track).with(event)
         event.save
       end
+
+      it 'does not call UserContributedProjects.track if its not yet available' do
+        expect(UserContributedProjects).to receive(:available?).and_return(false)
+        expect(UserContributedProjects).not_to receive(:track)
+        event.save
+      end
     end
   end
 

spec/models/user_contributed_projects_spec.rb

@@ -40,6 +40,21 @@ describe UserContributedProjects do
     end
   end
 
+  describe '.available?' do
+    before do
+      described_class.instance_variable_set('@available_flag', nil)
+    end
+
+    it 'checks schema version and properly caches positive result' do
+      expect(ActiveRecord::Migrator).to receive(:current_version).and_return(described_class::REQUIRED_SCHEMA_VERSION - 1 - rand(1000))
+      expect(described_class.available?).to be_falsey
+      expect(ActiveRecord::Migrator).to receive(:current_version).and_return(described_class::REQUIRED_SCHEMA_VERSION + rand(1000))
+      expect(described_class.available?).to be_truthy
+      expect(ActiveRecord::Migrator).not_to receive(:current_version)
+      expect(described_class.available?).to be_truthy # cached response
+    end
+  end
+
   it { is_expected.to validate_presence_of(:project) }
   it { is_expected.to validate_presence_of(:user) }
 end