Merge branch 'cache-last-usage-data' into 'master'

Cache the last usage data to avoid unicorn timeouts

On GitLab.com, the usage data cache was never populated because it takes longer than 60 seconds to generate.

This MR also improves usage data performance. The Event default_scope was causing the query to use the wrong index, causing the query to scan through all rows unnecessarily.

Closes #1044

See merge request !779

CHANGELOG-EE.md

@@ -2,6 +2,7 @@ Please view this file on the master branch, on stable branches it's out of date.
 
 ## 8.13.0 (2016-10-22)
 
+  - Cache the last usage data to avoid unicorn timeouts
   - Add user activity table and service to query for active users
   - Fix 500 error updating mirror URLs for projects
   - Restrict protected branch access to specific groups !645

app/workers/gitlab_usage_ping_worker.rb

@@ -15,7 +15,7 @@ class GitlabUsagePingWorker
 
     begin
       HTTParty.post(url,
-                    body: Gitlab::UsageData.to_json,
+                    body: Gitlab::UsageData.to_json(force_refresh: true),
                     headers: { 'Content-type' => 'application/json' }
                    )
     rescue HTTParty::Error => e

lib/gitlab/usage_data.rb

 module Gitlab
   class UsageData
     class << self
-      def data
-        Rails.cache.fetch('usage_data', expires_in: 1.hour) { uncached_data }
+      def data(force_refresh: false)
+        Rails.cache.fetch('usage_data', force: force_refresh, expires_in: 2.weeks) { uncached_data }
       end
 
       def uncached_data
         license_usage_data.merge(system_usage_data)
       end
 
-      def to_json
-        data.to_json
+      def to_json(force_refresh: false)
+        data(force_refresh: force_refresh).to_json
       end
 
       def system_usage_data
@@ -36,7 +36,8 @@ module Gitlab
             merge_requests: MergeRequest.count,
             milestones: Milestone.count,
             notes: Note.count,
-            pushes: Event.code_push.count,
+            # Default scope causes this query to run for a long time
+            pushes: Event.unscoped.code_push.count,
             pages_domains: PagesDomain.count,
             projects: Project.count,
             protected_branches: ProtectedBranch.count,

spec/workers/gitlab_usage_ping_worker_spec.rb

@@ -8,6 +8,7 @@ describe GitlabUsagePingWorker do
 
     stub_request(:post, "https://version.gitlab.com/usage_data").
         to_return(status: 200, body: '', headers: {})
+    expect(Gitlab::UsageData).to receive(:to_json).with({ force_refresh: true }).and_call_original
     expect(subject).to receive(:try_obtain_lease).and_return(true)
 
     expect(subject.perform.response.code.to_i).to eq(200)