Update docs and calculate process start time via proc table

This updates monitor docs to reflect the new ruby and unicorn metrics as
well as making it so we fetch process start time via the proc table
instead of via CLOCK_BOOTTIME

1 files changed, 11 insertions, 11 deletions

diff --git a/lib/gitlab/metrics/system.rb b/lib/gitlab/metrics/system.rb
index a269a8688e9..ecd558d7ec7 100644
--- a/lib/gitlab/metrics/system.rb
+++ b/lib/gitlab/metrics/system.rb
@@ -33,6 +33,13 @@ module Gitlab
 
           max_fds
         end
+
+        def self.process_start_time
+          start_time_in_jiffies = Sys::ProcTable.ps(pid: Process.pid).starttime
+          return 0 unless start_time_in_jiffies
+
+          start_time_in_jiffies / 100
+        end
       else
         def self.memory_usage
           0.0
@@ -45,6 +52,10 @@ module Gitlab
         def self.max_open_file_descriptors
           0
         end
+
+        def self.process_start_time
+          0
+        end
       end
 
       # THREAD_CPUTIME is not supported on OS X
@@ -60,17 +71,6 @@ module Gitlab
         end
       end
 
-      # CLOCK_BOOTTIME is not supported on OS X
-      if Process.const_defined?(:CLOCK_BOOTTIME)
-        def self.process_start_time
-          Process
-            .clock_gettime(Process::CLOCK_BOOTTIME, :float_second)
-        end
-      else
-        def self.process_start_time
-          0.0
-        end
-      end
       # Returns the current real time in a given precision.
       #
       # Returns the time as a Float for precision = :float_second.