Handle unavailable system info

For Linux with the grsecurity patches applied, paths in `/proc` may not
be readable, so handle those cases and show a message rather than
blowing up.

CHANGELOG

@@ -10,6 +10,9 @@ v 8.12.0 (unreleased)
   - Added tests for diff notes
   - Added 'only_allow_merge_if_build_succeeds' project setting in the API. !5930 (Duck)
 
+v 8.11.3 (unreleased)
+  - Allow system info page to handle case where info is unavailable
+
 v 8.11.2 (unreleased)
   - Show "Create Merge Request" widget for push events to fork projects on the source project
 

app/controllers/admin/system_info_controller.rb

@@ -29,7 +29,8 @@ class Admin::SystemInfoController < Admin::ApplicationController
   ]
 
   def show
-    system_info = Vmstat.snapshot
+    @cpus = Vmstat.cpu rescue nil
+    @memory = Vmstat.memory rescue nil
     mounts = Sys::Filesystem.mounts
 
     @disks = []
@@ -50,10 +51,5 @@ class Admin::SystemInfoController < Admin::ApplicationController
       rescue Sys::Filesystem::Error
       end
     end
-
-    @cpus = system_info.cpus.length
-
-    @mem_used = system_info.memory.active_bytes
-    @mem_total = system_info.memory.total_bytes
   end
 end

app/views/admin/system_info/show.html.haml

@@ -9,12 +9,20 @@
       .light-well
         %h4 CPU
         .data
-          %h1= "#{@cpus} cores"
+          - if @cpus
+            %h1= "#{@cpus.length} cores"
+          - else
+            %i.fa.fa-warning.text-warning
+            Unable to collect CPU info
     .col-sm-4
       .light-well
         %h4 Memory
         .data
-          %h1= "#{number_to_human_size(@mem_used)} / #{number_to_human_size(@mem_total)}"
+          - if @memory
+            %h1= "#{number_to_human_size(@memory.active_bytes)} / #{number_to_human_size(@memory.total_bytes)}"
+          - else
+            %i.fa.fa-warning.text-warning
+            Unable to collect memory info
     .col-sm-4
       .light-well
         %h4 Disks

spec/features/admin/admin_system_info_spec.rb

@@ -6,12 +6,49 @@ describe 'Admin System Info' do
   end
 
   describe 'GET /admin/system_info' do
+    let(:cpu) { double(:cpu, length: 2) }
+    let(:memory) { double(:memory, active_bytes: 4294967296, total_bytes: 17179869184) }
+
+    context 'when all info is available' do
+      before do
+        allow(Vmstat).to receive(:cpu).and_return(cpu)
+        allow(Vmstat).to receive(:memory).and_return(memory)
+        visit admin_system_info_path
+      end
+
       it 'shows system info page' do
+        expect(page).to have_content 'CPU 2 cores'
+        expect(page).to have_content 'Memory 4 GB / 16 GB'
+        expect(page).to have_content 'Disks'
+      end
+    end
+
+    context 'when CPU info is not available' do
+      before do
+        allow(Vmstat).to receive(:cpu).and_raise(Errno::ENOENT)
+        allow(Vmstat).to receive(:memory).and_return(memory)
         visit admin_system_info_path
+      end
+
+      it 'shows system info page with no CPU info' do
+        expect(page).to have_content 'CPU Unable to collect CPU info'
+        expect(page).to have_content 'Memory 4 GB / 16 GB'
+        expect(page).to have_content 'Disks'
+      end
+    end
 
-      expect(page).to have_content 'CPU'
-      expect(page).to have_content 'Memory'
+    context 'when memory info is not available' do
+      before do
+        allow(Vmstat).to receive(:cpu).and_return(cpu)
+        allow(Vmstat).to receive(:memory).and_raise(Errno::ENOENT)
+        visit admin_system_info_path
+      end
+
+      it 'shows system info page with no CPU info' do
+        expect(page).to have_content 'CPU 2 cores'
+        expect(page).to have_content 'Memory Unable to collect memory info'
         expect(page).to have_content 'Disks'
       end
     end
+  end
 end