Use separate series for Rails/Sidekiq sample stats

This removes the need for any tags to differentiate between Sidekiq and
Rails statistics while still being able to separate the two.

lib/gitlab/metrics/sampler.rb

@@ -50,12 +50,11 @@ module Gitlab
       end
 
       def sample_memory_usage
-        @metrics << Metric.new('memory_usage', value: System.memory_usage)
+        add_metric('memory_usage', value: System.memory_usage)
       end
 
       def sample_file_descriptors
-        @metrics << Metric.
-          new('file_descriptors', value: System.file_descriptor_count)
+        add_metric('file_descriptors', value: System.file_descriptor_count)
       end
 
       if Metrics.mri?
@@ -69,7 +68,7 @@ module Gitlab
           counts['Symbol'] = Symbol.all_symbols.length
 
           counts.each do |name, count|
-            @metrics << Metric.new('object_counts', { count: count }, type: name)
+            add_metric('object_counts', { count: count }, type: name)
           end
         end
       else
@@ -91,7 +90,17 @@ module Gitlab
 
         stats[:count] = stats[:minor_gc_count] + stats[:major_gc_count]
 
-        @metrics << Metric.new('gc_statistics', stats)
+        add_metric('gc_statistics', stats)
+      end
+
+      def add_metric(series, values, tags = {})
+        prefix = sidekiq? ? 'sidekiq_' : 'rails_'
+
+        @metrics << Metric.new("#{prefix}#{series}", values, tags)
+      end
+
+      def sidekiq?
+        Sidekiq.server?
       end
     end
   end

spec/lib/gitlab/metrics/sampler_spec.rb

@@ -51,8 +51,8 @@ describe Gitlab::Metrics::Sampler do
       expect(Gitlab::Metrics::System).to receive(:memory_usage).
         and_return(9000)
 
-      expect(Gitlab::Metrics::Metric).to receive(:new).
-        with('memory_usage', value: 9000).
+      expect(sampler).to receive(:add_metric).
+        with(/memory_usage/, value: 9000).
         and_call_original
 
       sampler.sample_memory_usage
@@ -64,8 +64,8 @@ describe Gitlab::Metrics::Sampler do
       expect(Gitlab::Metrics::System).to receive(:file_descriptor_count).
         and_return(4)
 
-      expect(Gitlab::Metrics::Metric).to receive(:new).
-        with('file_descriptors', value: 4).
+      expect(sampler).to receive(:add_metric).
+        with(/file_descriptors/, value: 4).
         and_call_original
 
       sampler.sample_file_descriptors
@@ -74,8 +74,8 @@ describe Gitlab::Metrics::Sampler do
 
   describe '#sample_objects' do
     it 'adds a metric containing the amount of allocated objects' do
-      expect(Gitlab::Metrics::Metric).to receive(:new).
-        with('object_counts', an_instance_of(Hash), an_instance_of(Hash)).
+      expect(sampler).to receive(:add_metric).
+        with(/object_counts/, an_instance_of(Hash), an_instance_of(Hash)).
         at_least(:once).
         and_call_original
 
@@ -87,11 +87,33 @@ describe Gitlab::Metrics::Sampler do
     it 'adds a metric containing garbage collection statistics' do
       expect(GC::Profiler).to receive(:total_time).and_return(0.24)
 
-      expect(Gitlab::Metrics::Metric).to receive(:new).
-        with('gc_statistics', an_instance_of(Hash)).
+      expect(sampler).to receive(:add_metric).
+        with(/gc_statistics/, an_instance_of(Hash)).
         and_call_original
 
       sampler.sample_gc
     end
   end
+
+  describe '#add_metric' do
+    it 'prefixes the series name for a Rails process' do
+      expect(sampler).to receive(:sidekiq?).and_return(false)
+
+      expect(Gitlab::Metrics::Metric).to receive(:new).
+        with('rails_cats', { value: 10 }, {}).
+        and_call_original
+
+      sampler.add_metric('cats', value: 10)
+    end
+
+    it 'prefixes the series name for a Sidekiq process' do
+      expect(sampler).to receive(:sidekiq?).and_return(true)
+
+      expect(Gitlab::Metrics::Metric).to receive(:new).
+        with('sidekiq_cats', { value: 10 }, {}).
+        and_call_original
+
+      sampler.add_metric('cats', value: 10)
+    end
+  end
 end