1 files changed, 234 insertions, 0 deletions
diff --git a/spec/lib/gitlab/metrics/instrumentation_spec.rb b/spec/lib/gitlab/metrics/instrumentation_spec.rb
new file mode 100644
index 00000000000..a7eab9d11cc
--- /dev/null
+++ b/spec/lib/gitlab/metrics/instrumentation_spec.rb
@@ -0,0 +1,234 @@
+require 'spec_helper'
+
+describe Gitlab::Metrics::Instrumentation do
+  let(:transaction) { Gitlab::Metrics::Transaction.new }
+
+  before do
+    @dummy = Class.new do
+      def self.foo(text = 'foo')
+        text
+      end
+
+      def bar(text = 'bar')
+        text
+      end
+    end
+
+    allow(@dummy).to receive(:name).and_return('Dummy')
+  end
+
+  describe '.configure' do
+    it 'yields self' do
+      described_class.configure do |c|
+        expect(c).to eq(described_class)
+      end
+    end
+  end
+
+  describe '.instrument_method' do
+    describe 'with metrics enabled' do
+      before do
+        allow(Gitlab::Metrics).to receive(:enabled?).and_return(true)
+
+        described_class.instrument_method(@dummy, :foo)
+      end
+
+      it 'renames the original method' do
+        expect(@dummy).to respond_to(:_original_foo)
+      end
+
+      it 'calls the instrumented method with the correct arguments' do
+        expect(@dummy.foo).to eq('foo')
+      end
+
+      it 'tracks the call duration upon calling the method' do
+        allow(Gitlab::Metrics).to receive(:method_call_threshold).
+          and_return(0)
+
+        allow(described_class).to receive(:transaction).
+          and_return(transaction)
+
+        expect(transaction).to receive(:add_metric).
+          with(described_class::SERIES, an_instance_of(Hash),
+               method: 'Dummy.foo')
+
+        @dummy.foo
+      end
+
+      it 'does not track method calls below a given duration threshold' do
+        allow(Gitlab::Metrics).to receive(:method_call_threshold).
+          and_return(100)
+
+        expect(transaction).to_not receive(:add_metric)
+
+        @dummy.foo
+      end
+    end
+
+    describe 'with metrics disabled' do
+      before do
+        allow(Gitlab::Metrics).to receive(:enabled?).and_return(false)
+      end
+
+      it 'does not instrument the method' do
+        described_class.instrument_method(@dummy, :foo)
+
+        expect(@dummy).to_not respond_to(:_original_foo)
+      end
+    end
+  end
+
+  describe '.instrument_instance_method' do
+    describe 'with metrics enabled' do
+      before do
+        allow(Gitlab::Metrics).to receive(:enabled?).and_return(true)
+
+        described_class.
+          instrument_instance_method(@dummy, :bar)
+      end
+
+      it 'renames the original method' do
+        expect(@dummy.method_defined?(:_original_bar)).to eq(true)
+      end
+
+      it 'calls the instrumented method with the correct arguments' do
+        expect(@dummy.new.bar).to eq('bar')
+      end
+
+      it 'tracks the call duration upon calling the method' do
+        allow(Gitlab::Metrics).to receive(:method_call_threshold).
+          and_return(0)
+
+        allow(described_class).to receive(:transaction).
+          and_return(transaction)
+
+        expect(transaction).to receive(:add_metric).
+          with(described_class::SERIES, an_instance_of(Hash),
+               method: 'Dummy#bar')
+
+        @dummy.new.bar
+      end
+
+      it 'does not track method calls below a given duration threshold' do
+        allow(Gitlab::Metrics).to receive(:method_call_threshold).
+          and_return(100)
+
+        expect(transaction).to_not receive(:add_metric)
+
+        @dummy.new.bar
+      end
+    end
+
+    describe 'with metrics disabled' do
+      before do
+        allow(Gitlab::Metrics).to receive(:enabled?).and_return(false)
+      end
+
+      it 'does not instrument the method' do
+        described_class.
+          instrument_instance_method(@dummy, :bar)
+
+        expect(@dummy.method_defined?(:_original_bar)).to eq(false)
+      end
+    end
+  end
+
+  describe '.instrument_class_hierarchy' do
+    before do
+      allow(Gitlab::Metrics).to receive(:enabled?).and_return(true)
+
+      @child1 = Class.new(@dummy) do
+        def self.child1_foo; end
+        def child1_bar; end
+      end
+
+      @child2 = Class.new(@child1) do
+        def self.child2_foo; end
+        def child2_bar; end
+      end
+    end
+
+    it 'recursively instruments a class hierarchy' do
+      described_class.instrument_class_hierarchy(@dummy)
+
+      expect(@child1).to respond_to(:_original_child1_foo)
+      expect(@child2).to respond_to(:_original_child2_foo)
+
+      expect(@child1.method_defined?(:_original_child1_bar)).to eq(true)
+      expect(@child2.method_defined?(:_original_child2_bar)).to eq(true)
+    end
+
+    it 'does not instrument the root module' do
+      described_class.instrument_class_hierarchy(@dummy)
+
+      expect(@dummy).to_not respond_to(:_original_foo)
+      expect(@dummy.method_defined?(:_original_bar)).to eq(false)
+    end
+  end
+
+  describe '.instrument_methods' do
+    before do
+      allow(Gitlab::Metrics).to receive(:enabled?).and_return(true)
+    end
+
+    it 'instruments all public class methods' do
+      described_class.instrument_methods(@dummy)
+
+      expect(@dummy).to respond_to(:_original_foo)
+    end
+
+    it 'only instruments methods directly defined in the module' do
+      mod = Module.new do
+        def kittens
+        end
+      end
+
+      @dummy.extend(mod)
+
+      described_class.instrument_methods(@dummy)
+
+      expect(@dummy).to_not respond_to(:_original_kittens)
+    end
+
+    it 'can take a block to determine if a method should be instrumented' do
+      described_class.instrument_methods(@dummy) do
+        false
+      end
+
+      expect(@dummy).to_not respond_to(:_original_foo)
+    end
+  end
+
+  describe '.instrument_instance_methods' do
+    before do
+      allow(Gitlab::Metrics).to receive(:enabled?).and_return(true)
+    end
+
+    it 'instruments all public instance methods' do
+      described_class.instrument_instance_methods(@dummy)
+
+      expect(@dummy.method_defined?(:_original_bar)).to eq(true)
+    end
+
+    it 'only instruments methods directly defined in the module' do
+      mod = Module.new do
+        def kittens
+        end
+      end
+
+      @dummy.include(mod)
+
+      described_class.instrument_instance_methods(@dummy)
+
+      expect(@dummy.method_defined?(:_original_kittens)).to eq(false)
+    end
+
+    it 'can take a block to determine if a method should be instrumented' do
+      described_class.instrument_instance_methods(@dummy) do
+        false
+      end
+
+      expect(@dummy.method_defined?(:_original_bar)).to eq(false)
+    end
+  end
+end