Ruby sampler spec

spec/lib/gitlab/metrics/samplers/ruby_sampler_spec.rb

+require 'spec_helper'
+
+describe Gitlab::Metrics::Samplers::RubySampler do
+  let(:sampler) { described_class.new(5) }
+
+  after do
+    Allocations.stop if Gitlab::Metrics.mri?
+  end
+
+  describe '#sample' do
+    it 'samples various statistics' do
+      expect(Gitlab::Metrics::System).to receive(:memory_usage)
+      expect(Gitlab::Metrics::System).to receive(:file_descriptor_count)
+      expect(sampler).to receive(:sample_objects)
+      expect(sampler).to receive(:sample_gc)
+
+      sampler.sample
+    end
+
+    it 'adds a metric containing the memory usage' do
+      expect(Gitlab::Metrics::System).to receive(:memory_usage)
+                                           .and_return(9000)
+
+      expect(sampler.metrics[:memory_usage]).to receive(:set)
+                                                  .with({}, 9000)
+                                                  .and_call_original
+
+      sampler.sample
+    end
+
+    it 'adds a metric containing the amount of open file descriptors' do
+      expect(Gitlab::Metrics::System).to receive(:file_descriptor_count)
+                                           .and_return(4)
+
+      expect(sampler.metrics[:file_descriptors]).to receive(:set)
+                                                      .with({}, 4)
+                                                      .and_call_original
+
+      sampler.sample
+    end
+
+    it 'clears any GC profiles' do
+      expect(GC::Profiler).to receive(:clear)
+
+      sampler.sample
+    end
+  end
+
+  describe '#sample_gc' do
+    it 'adds a metric containing garbage collection time statistics' do
+      expect(GC::Profiler).to receive(:total_time).and_return(0.24)
+
+
+      expect(sampler.metrics[:total_time]).to receive(:set)
+                                                .with({}, 240)
+                                                .and_call_original
+
+      sampler.sample
+    end
+
+    it 'adds a metric containing garbage collection statistics' do
+      GC.stat.keys.each do |key|
+        expect(sampler.metrics[key]).to receive(:set).with({}, anything).and_call_original
+      end
+
+      sampler.sample
+    end
+  end
+
+  if Gitlab::Metrics.mri?
+    describe '#sample_objects' do
+      it 'adds a metric containing the amount of allocated objects' do
+        expect(sampler.metrics[:objects_total]).to receive(:set)
+                                                     .with(include(class: anything), be > 0)
+                                                     .at_least(:once)
+                                                     .and_call_original
+
+        sampler.sample
+      end
+
+      it 'ignores classes without a name' do
+        expect(Allocations).to receive(:to_hash).and_return({ Class.new => 4 })
+
+
+        expect(sampler.metrics[:objects_total]).not_to receive(:set)
+                                                         .with(include(class: 'object_counts'), anything)
+
+        sampler.sample
+      end
+    end
+  end
+end