FEATURE: warn the admin whenever we disable the download_remote_images_to_local site setting

config/locales/server.en.yml

@@ -1282,6 +1282,10 @@ en:
 
         [Please review them in the admin section](%{base_url}/admin/users/list/pending).
 
+    download_remote_images_disabled:
+      subject_template: "Download remote images has been disabled"
+      text_body_template: "You previously had the `download_remote_images_to_local` setting enabled but the `download_remote_images_threshold` has been hit."
+
   unsubscribe_link: "To unsubscribe from these emails, visit your [user preferences](%{user_preferences_url})."
 
   user_notifications:

lib/cooked_post_processor.rb

@@ -236,6 +236,7 @@ class CookedPostProcessor
   def disable_if_low_on_disk_space
     if available_disk_space < SiteSetting.download_remote_images_threshold
       SiteSetting.download_remote_images_to_local = false
+      SystemMessage.create(Discourse.site_contact_user, :download_remote_images_disabled)
       return true
     end
     false

spec/components/cooked_post_processor_spec.rb

@@ -295,20 +295,23 @@ describe CookedPostProcessor do
 
       before { SiteSetting.stubs(:download_remote_images_to_local).returns(true) }
 
-      it "runs only when a user updated the post" do
+      it "does not run when there is not enough disk space" do
+        cpp.expects(:disable_if_low_on_disk_space).returns(true)
+        Jobs.expects(:cancel_scheduled_job).never
+        cpp.pull_hotlinked_images
+      end
+
+      context "and there is enough disk space" do
+
+        before { cpp.expects(:disable_if_low_on_disk_space).returns(false) }
+
+        it "does not run when the system user updated the post" do
           post.last_editor_id = Discourse.system_user.id
           Jobs.expects(:cancel_scheduled_job).never
           cpp.pull_hotlinked_images
         end
 
-      it "disables download when disk space is low" do
+        context "and the post has been updated by an actual user" do
-        SiteSetting.expects(:download_remote_images_threshold).returns(20)
-        cpp.expects(:available_disk_space).returns(10)
-        Jobs.expects(:cancel_scheduled_job).never
-        cpp.pull_hotlinked_images
-      end
-
-      context "and the post has been updated by a user" do
 
           before { post.id = 42 }
 
@@ -327,6 +330,8 @@ describe CookedPostProcessor do
 
     end
 
+  end
+
   context ".disable_if_low_on_disk_space" do
 
     let(:post) { build(:post) }
@@ -340,14 +345,20 @@ describe CookedPostProcessor do
       cpp.disable_if_low_on_disk_space.should == false
     end
 
-    it "disables download_remote_images_threshold when there's not enough disk space" do
+    context "when there's not enough disk space" do
-      SiteSetting.expects(:download_remote_images_threshold).returns(75)
+
+      before { SiteSetting.expects(:download_remote_images_threshold).returns(75) }
+
+      it "disables download_remote_images_threshold and send a notification to the admin" do
+        SystemMessage.expects(:create).with(Discourse.site_contact_user, :download_remote_images_disabled).once
         cpp.disable_if_low_on_disk_space.should == true
         SiteSetting.download_remote_images_to_local.should == false
       end
 
     end
 
+  end
+
   context ".is_a_hyperlink?" do
 
     let(:post) { build(:post) }