Add tests for metrics behavior

lib/gitlab/metrics.rb

@@ -54,23 +54,25 @@ module Gitlab
     end
 
     def self.counter(name, docstring, base_labels = {})
-      dummy_metric || registry.get(name) || registry.counter(name, docstring, base_labels)
+      provide_metric(name) || registry.counter(name, docstring, base_labels)
     end
 
     def self.summary(name, docstring, base_labels = {})
-      dummy_metric || registry.get(name) || registry.summary(name, docstring, base_labels)
+      provide_metric(name) || registry.summary(name, docstring, base_labels)
     end
 
     def self.gauge(name, docstring, base_labels = {})
-      dummy_metric || registry.get(name) || registry.gauge(name, docstring, base_labels)
+      provide_metric(name) || registry.gauge(name, docstring, base_labels)
     end
 
-    def self.histogram(name, docstring, base_labels = {}, buckets = Histogram::DEFAULT_BUCKETS)
-      dummy_metric || registry.get(name) || registry.histogram(name, docstring, base_labels, buckets)
+    def self.histogram(name, docstring, base_labels = {}, buckets = ::Prometheus::Client::Histogram::DEFAULT_BUCKETS)
+      provide_metric(name) || registry.histogram(name, docstring, base_labels, buckets)
     end
 
-    def self.dummy_metric
-      unless prometheus_metrics_enabled?
+    def self.provide_metric(name)
+      if prometheus_metrics_enabled?
+        registry.get(name)
+      else
         DummyMetric.new
       end
     end

spec/lib/gitlab/metrics_spec.rb

@@ -13,6 +13,18 @@ describe Gitlab::Metrics do
     end
   end
 
+  describe '.prometheus_metrics_enabled?' do
+    it 'returns a boolean' do
+      expect([true, false].include?(described_class.prometheus_metrics_enabled?)).to eq(true)
+    end
+  end
+
+  describe '.influx_metrics_enabled?' do
+    it 'returns a boolean' do
+      expect([true, false].include?(described_class.influx_metrics_enabled?)).to eq(true)
+    end
+  end
+
   describe '.submit_metrics' do
     it 'prepares and writes the metrics to InfluxDB' do
       connection = double(:connection)
@@ -177,4 +189,117 @@ describe Gitlab::Metrics do
       end
     end
   end
+
+  shared_examples 'prometheus metrics API' do
+    describe '#counter' do
+      subject { described_class.counter(:couter, 'doc') }
+
+      describe '#increment' do
+        it { expect { subject.increment }.not_to raise_exception }
+        it { expect { subject.increment({}) }.not_to raise_exception }
+        it { expect { subject.increment({}, 1) }.not_to raise_exception }
+      end
+    end
+
+    describe '#summary' do
+      subject { described_class.summary(:summary, 'doc') }
+
+      describe '#observe' do
+        it { expect { subject.observe({}, 2) }.not_to raise_exception }
+      end
+    end
+
+    describe '#gauge' do
+      subject { described_class.gauge(:gauge, 'doc') }
+
+      describe '#observe' do
+        it { expect { subject.set({}, 1) }.not_to raise_exception }
+      end
+    end
+
+    describe '#histogram' do
+      subject { described_class.histogram(:histogram, 'doc') }
+
+      describe '#observe' do
+        it { expect { subject.observe({}, 2) }.not_to raise_exception }
+      end
+    end
+  end
+
+  context 'prometheus metrics disabled' do
+    before do
+      allow(described_class).to receive(:prometheus_metrics_enabled?).and_return(false)
+    end
+
+    it_behaves_like 'prometheus metrics API'
+
+    describe '#dummy_metric' do
+      subject { described_class.provide_metric(:test) }
+
+      it { is_expected.to be_a(Gitlab::Metrics::DummyMetric) }
+    end
+
+    describe '#counter' do
+      subject { described_class.counter(:counter, 'doc') }
+
+      it { is_expected.to be_a(Gitlab::Metrics::DummyMetric) }
+
+    end
+
+    describe '#summary' do
+      subject { described_class.summary(:summary, 'doc') }
+
+      it { is_expected.to be_a(Gitlab::Metrics::DummyMetric) }
+    end
+
+    describe '#gauge' do
+      subject { described_class.gauge(:gauge, 'doc') }
+
+      it { is_expected.to be_a(Gitlab::Metrics::DummyMetric) }
+    end
+
+    describe '#histogram' do
+      subject { described_class.histogram(:histogram, 'doc') }
+
+      it { is_expected.to be_a(Gitlab::Metrics::DummyMetric) }
+    end
+  end
+
+  context 'prometheus metrics enabled' do
+    before do
+      allow(described_class).to receive(:prometheus_metrics_enabled?).and_return(true)
+    end
+
+    it_behaves_like 'prometheus metrics API'
+
+    describe '#dummy_metric' do
+      subject { described_class.provide_metric(:test) }
+
+      it { is_expected.to be_nil }
+    end
+
+    describe '#counter' do
+      subject { described_class.counter(:name, 'doc') }
+
+      it { is_expected.not_to be_a(Gitlab::Metrics::DummyMetric) }
+    end
+
+    describe '#summary' do
+      subject { described_class.summary(:name, 'doc') }
+
+      it { is_expected.not_to be_a(Gitlab::Metrics::DummyMetric) }
+    end
+
+    describe '#gauge' do
+      subject { described_class.gauge(:name, 'doc') }
+
+      it { is_expected.not_to be_a(Gitlab::Metrics::DummyMetric) }
+    end
+
+    describe '#histogram' do
+      subject { described_class.histogram(:name, 'doc') }
+
+      it { is_expected.not_to be_a(Gitlab::Metrics::DummyMetric) }
+    end
+  end
 end