Merge branch 'master' into issue_3508issue_3508

3 files changed, 71 insertions, 1 deletions

diff --git a/lib/gitlab/metrics/metric.rb b/lib/gitlab/metrics/metric.rb
index 7ea9555cc8c..1cd1ca30f70 100644
--- a/lib/gitlab/metrics/metric.rb
+++ b/lib/gitlab/metrics/metric.rb
@@ -2,6 +2,8 @@ module Gitlab
   module Metrics
     # Class for storing details of a single metric (label, value, etc).
     class Metric
+      JITTER_RANGE = 0.000001..0.001
+
       attr_reader :series, :values, :tags, :created_at
 
       # series - The name of the series (as a String) to store the metric in.
@@ -16,11 +18,29 @@ module Gitlab
 
       # Returns a Hash in a format that can be directly written to InfluxDB.
       def to_hash
+        # InfluxDB overwrites an existing point if a new point has the same
+        # series, tag set, and timestamp. In a highly concurrent environment
+        # this means that using the number of seconds since the Unix epoch is
+        # inevitably going to collide with another timestamp. For example, two
+        # Rails requests processed by different processes may end up generating
+        # metrics using the _exact_ same timestamp (in seconds).
+        #
+        # Due to the way InfluxDB is set up there's no solution to this problem,
+        # all we can do is lower the amount of collisions. We do this by using
+        # Time#to_f which returns the seconds as a Float providing greater
+        # accuracy. We then add a small random value that is large enough to
+        # distinguish most timestamps but small enough to not alter the amount
+        # of seconds.
+        #
+        # See https://gitlab.com/gitlab-com/operations/issues/175 for more
+        # information.
+        time = @created_at.to_f + rand(JITTER_RANGE)
+
         {
           series:    @series,
           tags:      @tags,
           values:    @values,
-          timestamp: @created_at.to_i * 1_000_000_000
+          timestamp: (time * 1_000_000_000).to_i
         }
       end
     end
diff --git a/lib/gitlab/metrics/subscribers/rails_cache.rb b/lib/gitlab/metrics/subscribers/rails_cache.rb
new file mode 100644
index 00000000000..49e5f86e6e6
--- /dev/null
+++ b/lib/gitlab/metrics/subscribers/rails_cache.rb
@@ -0,0 +1,39 @@
+module Gitlab
+  module Metrics
+    module Subscribers
+      # Class for tracking the total time spent in Rails cache calls
+      class RailsCache < ActiveSupport::Subscriber
+        attach_to :active_support
+
+        def cache_read(event)
+          increment(:cache_read_duration, event.duration)
+        end
+
+        def cache_write(event)
+          increment(:cache_write_duration, event.duration)
+        end
+
+        def cache_delete(event)
+          increment(:cache_delete_duration, event.duration)
+        end
+
+        def cache_exist?(event)
+          increment(:cache_exists_duration, event.duration)
+        end
+
+        def increment(key, duration)
+          return unless current_transaction
+
+          current_transaction.increment(:cache_duration, duration)
+          current_transaction.increment(key, duration)
+        end
+
+        private
+
+        def current_transaction
+          Transaction.current
+        end
+      end
+    end
+  end
+end
diff --git a/lib/gitlab/metrics/system.rb b/lib/gitlab/metrics/system.rb
index 83371265278..a7d183b2f94 100644
--- a/lib/gitlab/metrics/system.rb
+++ b/lib/gitlab/metrics/system.rb
@@ -30,6 +30,17 @@ module Gitlab
           0
         end
       end
+
+      # THREAD_CPUTIME is not supported on OS X
+      if Process.const_defined?(:CLOCK_THREAD_CPUTIME_ID)
+        def self.cpu_time
+          Process.clock_gettime(Process::CLOCK_THREAD_CPUTIME_ID, :millisecond)
+        end
+      else
+        def self.cpu_time
+          Process.clock_gettime(Process::CLOCK_PROCESS_CPUTIME_ID, :millisecond)
+        end
+      end
     end
   end
 end