Merge branch 'project-cache-worker-lease' into 'master'

Restrict ProjectCacheWorker jobs to one per 15 min

## What does this MR do?

This restricts performing ProjectCacheWorker jobs to once every 15 minutes per project. The goal of this is to reduce disk load in the event of a lot of pushes happening in a short period of time. 

The impact is that cached data (e.g. commit count) may be updated less frequently. Furthermore it could mean that separate push payloads won't lead to e.g. READMEs being updated. Most of the cached data isn't updated very frequently, so this trade off should be worth it considering the alternative is a burning storage layer. 

In the future we'll have to flush caches in a smarter way. For example, refreshing the README cache could probably be done separately from the other caches with its own lease and such. See https://gitlab.com/gitlab-org/gitlab-ce/issues/23550 for more information.

See merge request !7017

1 files changed, 28 insertions, 10 deletions

diff --git a/spec/workers/project_cache_worker_spec.rb b/spec/workers/project_cache_worker_spec.rb
index 5785a6a06ff..f5b60b90d11 100644
--- a/spec/workers/project_cache_worker_spec.rb
+++ b/spec/workers/project_cache_worker_spec.rb
@@ -6,21 +6,39 @@ describe ProjectCacheWorker do
   subject { described_class.new }
 
   describe '#perform' do
-    it 'updates project cache data' do
-      expect_any_instance_of(Repository).to receive(:size)
-      expect_any_instance_of(Repository).to receive(:commit_count)
+    context 'when an exclusive lease can be obtained' do
+      before do
+        allow(subject).to receive(:try_obtain_lease_for).with(project.id).
+          and_return(true)
+      end
 
-      expect_any_instance_of(Project).to receive(:update_repository_size)
-      expect_any_instance_of(Project).to receive(:update_commit_count)
+      it 'updates project cache data' do
+        expect_any_instance_of(Repository).to receive(:size)
+        expect_any_instance_of(Repository).to receive(:commit_count)
 
-      subject.perform(project.id)
+        expect_any_instance_of(Project).to receive(:update_repository_size)
+        expect_any_instance_of(Project).to receive(:update_commit_count)
+
+        subject.perform(project.id)
+      end
+
+      it 'handles missing repository data' do
+        expect_any_instance_of(Repository).to receive(:exists?).and_return(false)
+        expect_any_instance_of(Repository).not_to receive(:size)
+
+        subject.perform(project.id)
+      end
     end
 
-    it 'handles missing repository data' do
-      expect_any_instance_of(Repository).to receive(:exists?).and_return(false)
-      expect_any_instance_of(Repository).not_to receive(:size)
+    context 'when an exclusive lease can not be obtained' do
+      it 'does nothing' do
+        allow(subject).to receive(:try_obtain_lease_for).with(project.id).
+          and_return(false)
+
+        expect(subject).not_to receive(:update_caches)
 
-      subject.perform(project.id)
+        subject.perform(project.id)
+      end
     end
   end
 end