Allow disabling usage ping in `gitlab.yml`

Setting `usage_ping_enabled` to false in `gitlab.yml`:

1. Disables the usage ping, regardless of the value stored in the database.
2. Prevents the usage ping from being enabled through the admin panel. It can
   only be enabled by either removing the line from `gitlab.yml` and configuring
   through the admin panel, or setting it to true in `gitlab.yml`.

2 files changed, 23 insertions, 8 deletions

diff --git a/app/models/application_setting.rb b/app/models/application_setting.rb
index 54f01f8637e..043f57241a3 100644
--- a/app/models/application_setting.rb
+++ b/app/models/application_setting.rb
@@ -246,7 +246,7 @@ class ApplicationSetting < ActiveRecord::Base
       two_factor_grace_period: 48,
       user_default_external: false,
       polling_interval_multiplier: 1,
-      usage_ping_enabled: true
+      usage_ping_enabled: Settings.gitlab['usage_ping_enabled']
     }
   end
 
@@ -349,6 +349,14 @@ class ApplicationSetting < ActiveRecord::Base
     sidekiq_throttling_enabled
   end
 
+  def usage_ping_can_be_configured?
+    Settings.gitlab.usage_ping_enabled
+  end
+
+  def usage_ping_enabled
+    usage_ping_can_be_configured? && super
+  end
+
   private
 
   def ensure_uuid!
diff --git a/app/views/admin/application_settings/_form.html.haml b/app/views/admin/application_settings/_form.html.haml
index 4b6628169ef..e1b4e34cd2b 100644
--- a/app/views/admin/application_settings/_form.html.haml
+++ b/app/views/admin/application_settings/_form.html.haml
@@ -502,17 +502,24 @@
             Let GitLab inform you when an update is available.
     .form-group
       .col-sm-offset-2.col-sm-10
+        - can_be_configured = @application_setting.usage_ping_can_be_configured?
         .checkbox
           = f.label :usage_ping_enabled do
-            = f.check_box :usage_ping_enabled
+            = f.check_box :usage_ping_enabled, disabled: !can_be_configured
             Usage ping enabled
-            = link_to icon('question-circle'), help_page_path("user/admin_area/settings/usage_statistics", anchor: "usage-data")
+            = link_to icon('question-circle'), help_page_path("user/admin_area/settings/usage_statistics", anchor: "usage-ping")
           .help-block
-            Every week GitLab will report license usage back to GitLab, Inc.
-            Disable this option if you do not want this to occur. To see the
-            JSON payload that will be sent, visit the
-            = succeed '.' do
-              = link_to "Cohorts page", admin_cohorts_path(anchor: 'usage-ping')
+            - if can_be_configured
+              Every week GitLab will report license usage back to GitLab, Inc.
+              Disable this option if you do not want this to occur. To see the
+              JSON payload that will be sent, visit the
+              = succeed '.' do
+                = link_to "Cohorts page", admin_cohorts_path(anchor: 'usage-ping')
+            - else
+              The usage ping is disabled, and cannot be configured through this
+              form. For more information, see the documentation on
+              = succeed '.' do
+                = link_to 'deactivating the usage ping', help_page_path('user/admin_area/settings/usage_statistics', anchor: 'deactivate-the-usage-ping')
 
   %fieldset
     %legend Email