Move pushes_since_gc to Redispushes-since-gc-redis

This moves tracking of the pushes since the last Git GC from PostgreSQL
to Redis. This reduces the number of writes on the "projects" table.
This in turn reduces the vacuuming overhead.

The lease used for incrementing the counter has been removed. This lease
was mostly put in place to prevent high database load but this isn't
needed anymore due to the counter now being stored in Redis.

Fixes gitlab-org/gitlab-ce#22125

2 files changed, 59 insertions, 22 deletions

diff --git a/spec/models/project_spec.rb b/spec/models/project_spec.rb
index 4a41fafb84d..74c1d93a460 100644
--- a/spec/models/project_spec.rb
+++ b/spec/models/project_spec.rb
@@ -1497,4 +1497,56 @@ describe Project, models: true do
       project.change_head(project.default_branch)
     end
   end
+
+  describe '#pushes_since_gc' do
+    let(:project) { create(:project) }
+
+    after do
+      project.reset_pushes_since_gc
+    end
+
+    context 'without any pushes' do
+      it 'returns 0' do
+        expect(project.pushes_since_gc).to eq(0)
+      end
+    end
+
+    context 'with a number of pushes' do
+      it 'returns the number of pushes' do
+        3.times { project.increment_pushes_since_gc }
+
+        expect(project.pushes_since_gc).to eq(3)
+      end
+    end
+  end
+
+  describe '#increment_pushes_since_gc' do
+    let(:project) { create(:project) }
+
+    after do
+      project.reset_pushes_since_gc
+    end
+
+    it 'increments the number of pushes since the last GC' do
+      3.times { project.increment_pushes_since_gc }
+
+      expect(project.pushes_since_gc).to eq(3)
+    end
+  end
+
+  describe '#reset_pushes_since_gc' do
+    let(:project) { create(:project) }
+
+    after do
+      project.reset_pushes_since_gc
+    end
+
+    it 'resets the number of pushes since the last GC' do
+      3.times { project.increment_pushes_since_gc }
+
+      project.reset_pushes_since_gc
+
+      expect(project.pushes_since_gc).to eq(0)
+    end
+  end
 end
diff --git a/spec/services/projects/housekeeping_service_spec.rb b/spec/services/projects/housekeeping_service_spec.rb
index ad0d58672b3..c6160f4fa57 100644
--- a/spec/services/projects/housekeeping_service_spec.rb
+++ b/spec/services/projects/housekeeping_service_spec.rb
@@ -4,12 +4,11 @@ describe Projects::HousekeepingService do
   subject { Projects::HousekeepingService.new(project) }
   let(:project) { create :project }
 
-  describe 'execute' do
-    before do
-      project.pushes_since_gc = 3
-      project.save!
-    end
+  after do
+    project.reset_pushes_since_gc
+  end
 
+  describe '#execute' do
     it 'enqueues a sidekiq job' do
       expect(subject).to receive(:try_obtain_lease).and_return(true)
       expect(GitGarbageCollectWorker).to receive(:perform_async).with(project.id)
@@ -32,12 +31,12 @@ describe Projects::HousekeepingService do
       it 'does not reset pushes_since_gc' do
         expect do
           expect { subject.execute }.to raise_error(Projects::HousekeepingService::LeaseTaken)
-        end.not_to change { project.pushes_since_gc }.from(3)
+        end.not_to change { project.pushes_since_gc }
       end
     end
   end
 
-  describe 'needed?' do
+  describe '#needed?' do
     it 'when the count is low enough' do
       expect(subject.needed?).to eq(false)
     end
@@ -48,25 +47,11 @@ describe Projects::HousekeepingService do
     end
   end
 
-  describe 'increment!' do
-    let(:lease_key) { "project_housekeeping:increment!:#{project.id}" }
-
+  describe '#increment!' do
     it 'increments the pushes_since_gc counter' do
-      lease = double(:lease, try_obtain: true)
-      expect(Gitlab::ExclusiveLease).to receive(:new).with(lease_key, anything).and_return(lease)
-
       expect do
         subject.increment!
       end.to change { project.pushes_since_gc }.from(0).to(1)
     end
-
-    it 'does not increment when no lease can be obtained' do
-      lease = double(:lease, try_obtain: false)
-      expect(Gitlab::ExclusiveLease).to receive(:new).with(lease_key, anything).and_return(lease)
-
-      expect do
-        subject.increment!
-      end.not_to change { project.pushes_since_gc }
-    end
   end
 end