Allow project housekeeping only once an hour

app/controllers/projects_controller.rb

@@ -170,10 +170,10 @@ class ProjectsController < ApplicationController
   end
 
   def housekeeping
-    ::Projects::HousekeepingService.new(@project).execute
+    message = ::Projects::HousekeepingService.new(@project).execute
 
     respond_to do |format|
-      flash[:notice] = "Housekeeping successfully started."
+      flash[:notice] = message
       format.html { redirect_to project_path(@project) }
     end
   end

app/services/projects/housekeeping_service.rb

@@ -9,12 +9,26 @@ module Projects
   class HousekeepingService < BaseService
     include Gitlab::ShellAdapter
 
+    LEASE_TIMEOUT = 3600
+
     def initialize(project)
       @project = project
     end
 
     def execute
+      if !try_obtain_lease
+        return "Housekeeping was already triggered in the past #{LEASE_TIMEOUT / 60} minutes"
+      end
+      
       GitlabShellWorker.perform_async(:gc, @project.path_with_namespace)
+      return "Housekeeping successfully started"
+    end
+
+    private
+
+    def try_obtain_lease
+      lease = ::Gitlab::ExclusiveLease.new("project_housekeeping:#{@project.id}", timeout: LEASE_TIMEOUT)
+      lease.try_obtain
     end
   end
 end

spec/services/projects/housekeeping_service_spec.rb

@@ -0,0 +1,40 @@
+require 'spec_helper'
+
+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
+
+    it 'enqueues a sidekiq job' do
+      expect(subject).to receive(:try_obtain_lease).and_return(true)
+      expect(GitlabShellWorker).to receive(:perform_async).with(:gc, project.path_with_namespace)
+
+      expect(subject.execute).to include('successfully started')
+      expect(project.pushes_since_gc).to eq(0)
+    end
+
+    it 'does not enqueue a job when no lease can be obtained' do
+      expect(subject).to receive(:try_obtain_lease).and_return(false)
+      expect(GitlabShellWorker).not_to receive(:perform_async)
+
+      expect(subject.execute).to include('already triggered')
+      expect(project.pushes_since_gc).to eq(3)
+    end
+  end
+
+  describe :needed? do
+    it 'when the count is low enough' do
+      expect(subject.needed?).to eq(false)
+    end
+
+    it 'when the count is high enough' do
+      allow(project).to receive(:pushes_since_gc).and_return(10)
+      expect(subject.needed?).to eq(true)
+    end
+  end
+end