1 files changed, 98 insertions, 0 deletions
diff --git a/lib/gitlab/metrics/sampler.rb b/lib/gitlab/metrics/sampler.rb
new file mode 100644
index 00000000000..998578e1c0a
--- /dev/null
+++ b/lib/gitlab/metrics/sampler.rb
@@ -0,0 +1,98 @@
+module Gitlab
+  module Metrics
+    # Class that sends certain metrics to InfluxDB at a specific interval.
+    #
+    # This class is used to gather statistics that can't be directly associated
+    # with a transaction such as system memory usage, garbage collection
+    # statistics, etc.
+    class Sampler
+      # interval - The sampling interval in seconds.
+      def initialize(interval = 15)
+        @interval = interval
+        @metrics  = []
+
+        @last_minor_gc = Delta.new(GC.stat[:minor_gc_count])
+        @last_major_gc = Delta.new(GC.stat[:major_gc_count])
+
+        if Gitlab::Metrics.mri?
+          require 'allocations'
+
+          Allocations.start
+        end
+      end
+
+      def start
+        Thread.new do
+          Thread.current.abort_on_exception = true
+
+          loop do
+            sleep(@interval)
+
+            sample
+          end
+        end
+      end
+
+      def sample
+        sample_memory_usage
+        sample_file_descriptors
+        sample_objects
+        sample_gc
+
+        flush
+      ensure
+        GC::Profiler.clear
+        @metrics.clear
+      end
+
+      def flush
+        Metrics.submit_metrics(@metrics.map(&:to_hash))
+      end
+
+      def sample_memory_usage
+        @metrics << Metric.new('memory_usage', value: System.memory_usage)
+      end
+
+      def sample_file_descriptors
+        @metrics << Metric.
+          new('file_descriptors', value: System.file_descriptor_count)
+      end
+
+      if Metrics.mri?
+        def sample_objects
+          sample = Allocations.to_hash
+          counts = sample.each_with_object({}) do |(klass, count), hash|
+            hash[klass.name] = count
+          end
+
+          # Symbols aren't allocated so we'll need to add those manually.
+          counts['Symbol'] = Symbol.all_symbols.length
+
+          counts.each do |name, count|
+            @metrics << Metric.new('object_counts', { count: count }, type: name)
+          end
+        end
+      else
+        def sample_objects
+        end
+      end
+
+      def sample_gc
+        time  = GC::Profiler.total_time * 1000.0
+        stats = GC.stat.merge(total_time: time)
+
+        # We want the difference of GC runs compared to the last sample, not the
+        # total amount since the process started.
+        stats[:minor_gc_count] =
+          @last_minor_gc.compared_with(stats[:minor_gc_count])
+
+        stats[:major_gc_count] =
+          @last_major_gc.compared_with(stats[:major_gc_count])
+
+        stats[:count] = stats[:minor_gc_count] + stats[:major_gc_count]
+
+        @metrics << Metric.new('gc_statistics', stats)
+      end
+    end
+  end
+end