1 files changed, 150 insertions, 0 deletions
diff --git a/spec/lib/gitlab/metrics/influx_sampler_spec.rb b/spec/lib/gitlab/metrics/influx_sampler_spec.rb
new file mode 100644
index 00000000000..999a9536d82
--- /dev/null
+++ b/spec/lib/gitlab/metrics/influx_sampler_spec.rb
@@ -0,0 +1,150 @@
+require 'spec_helper'
+
+describe Gitlab::Metrics::InfluxSampler do
+  let(:sampler) { described_class.new(5) }
+
+  after do
+    Allocations.stop if Gitlab::Metrics.mri?
+  end
+
+  describe '#start' do
+    it 'runs once and gathers a sample at a given interval' do
+      expect(sampler).to receive(:sleep).with(a_kind_of(Numeric)).twice
+      expect(sampler).to receive(:sample).once
+      expect(sampler).to receive(:running).and_return(true, false)
+
+      sampler.start.join
+    end
+  end
+
+  describe '#sample' do
+    it 'samples various statistics' do
+      expect(sampler).to receive(:sample_memory_usage)
+      expect(sampler).to receive(:sample_file_descriptors)
+      expect(sampler).to receive(:sample_objects)
+      expect(sampler).to receive(:sample_gc)
+      expect(sampler).to receive(:flush)
+
+      sampler.sample
+    end
+
+    it 'clears any GC profiles' do
+      expect(sampler).to receive(:flush)
+      expect(GC::Profiler).to receive(:clear)
+
+      sampler.sample
+    end
+  end
+
+  describe '#flush' do
+    it 'schedules the metrics using Sidekiq' do
+      expect(Gitlab::Metrics).to receive(:submit_metrics)
+        .with([an_instance_of(Hash)])
+
+      sampler.sample_memory_usage
+      sampler.flush
+    end
+  end
+
+  describe '#sample_memory_usage' do
+    it 'adds a metric containing the memory usage' do
+      expect(Gitlab::Metrics::System).to receive(:memory_usage)
+        .and_return(9000)
+
+      expect(sampler).to receive(:add_metric)
+        .with(/memory_usage/, value: 9000)
+        .and_call_original
+
+      sampler.sample_memory_usage
+    end
+  end
+
+  describe '#sample_file_descriptors' do
+    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).to receive(:add_metric)
+        .with(/file_descriptors/, value: 4)
+        .and_call_original
+
+      sampler.sample_file_descriptors
+    end
+  end
+
+  if Gitlab::Metrics.mri?
+    describe '#sample_objects' do
+      it 'adds a metric containing the amount of allocated objects' do
+        expect(sampler).to receive(:add_metric)
+          .with(/object_counts/, an_instance_of(Hash), an_instance_of(Hash))
+          .at_least(:once)
+          .and_call_original
+
+        sampler.sample_objects
+      end
+
+      it 'ignores classes without a name' do
+        expect(Allocations).to receive(:to_hash).and_return({ Class.new => 4 })
+
+        expect(sampler).not_to receive(:add_metric)
+          .with('object_counts', an_instance_of(Hash), type: nil)
+
+        sampler.sample_objects
+      end
+    end
+  end
+
+  describe '#sample_gc' do
+    it 'adds a metric containing garbage collection statistics' do
+      expect(GC::Profiler).to receive(:total_time).and_return(0.24)
+
+      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
+
+  describe '#sleep_interval' do
+    it 'returns a Numeric' do
+      expect(sampler.sleep_interval).to be_a_kind_of(Numeric)
+    end
+
+    # Testing random behaviour is very hard, so treat this test as a basic smoke
+    # test instead of a very accurate behaviour/unit test.
+    it 'does not return the same interval twice in a row' do
+      last = nil
+
+      100.times do
+        interval = sampler.sleep_interval
+
+        expect(interval).not_to eq(last)
+
+        last = interval
+      end
+    end
+  end
+end