Refresh project authorizations using a Redis lease

When I proposed using serializable transactions I was hoping we would be
able to refresh data of individual users concurrently. Unfortunately
upon closer inspection it was revealed this was not the case. This could
result in a lot of queries failing due to serialization errors,
overloading the database in the process (given enough workers trying to
update the target table).

To work around this we're now using a Redis lease that is cancelled upon
completion. This ensures we can update the data of different users
concurrently without overloading the database.

The code will try to obtain the lease until it succeeds, waiting at
least 1 second between retries. This is necessary as we may otherwise
end up _not_ updating the data which is not an option.

1 files changed, 17 insertions, 6 deletions

diff --git a/spec/workers/authorized_projects_worker_spec.rb b/spec/workers/authorized_projects_worker_spec.rb
index 18a1aab766c..95e2458da35 100644
--- a/spec/workers/authorized_projects_worker_spec.rb
+++ b/spec/workers/authorized_projects_worker_spec.rb
@@ -1,22 +1,33 @@
 require 'spec_helper'
 
 describe AuthorizedProjectsWorker do
+  let(:worker) { described_class.new }
+
   describe '#perform' do
     it "refreshes user's authorized projects" do
       user = create(:user)
 
-      expect(User).to receive(:find_by).with(id: user.id).and_return(user)
-      expect(user).to receive(:refresh_authorized_projects)
+      expect(worker).to receive(:refresh).with(an_instance_of(User))
 
-      described_class.new.perform(user.id)
+      worker.perform(user.id)
     end
 
-    context "when user is not found" do
+    context "when the user is not found" do
       it "does nothing" do
-        expect_any_instance_of(User).not_to receive(:refresh_authorized_projects)
+        expect(worker).not_to receive(:refresh)
 
-        described_class.new.perform(999_999)
+        described_class.new.perform(-1)
       end
     end
   end
+
+  describe '#refresh', redis: true do
+    it 'refreshes the authorized projects of the user' do
+      user = create(:user)
+
+      expect(user).to receive(:refresh_authorized_projects)
+
+      worker.refresh(user)
+    end
+  end
 end