SidekiqMetricsExporter tests

2 files changed, 128 insertions, 14 deletions

diff --git a/lib/gitlab/metrics/sidekiq_metrics_exporter.rb b/lib/gitlab/metrics/sidekiq_metrics_exporter.rb
index ce26fc97099..769a761e99e 100644
--- a/lib/gitlab/metrics/sidekiq_metrics_exporter.rb
+++ b/lib/gitlab/metrics/sidekiq_metrics_exporter.rb
@@ -10,15 +10,13 @@ module Gitlab
         MUTEX.synchronize do
           if @instance.nil?
             @instance = SidekiqMetricsExporter.new
-            at_exit(&@instance.method(:stop))
+            Kernel.at_exit(&@instance.method(:stop))
           end
         end
 
         @instance
       end
 
-      attr_reader :running
-
       def initialize
         @mutex = Mutex.new
       end
@@ -27,27 +25,25 @@ module Gitlab
         settings.enabled
       end
 
+      def running?
+        !thread.nil?
+      end
+
       def start
         return unless enabled?
 
         @mutex.synchronize do
-          return if running
-          @running = true
+          return thread if thread
 
           @thread = Thread.new do
             server_start
-            @running = false
           end
         end
       end
 
       def stop
         @mutex.synchronize do
-          return unless running
-
-          @running = false
-
-          if @thread
+          if thread
             @thread.wakeup if @thread.alive?
 
             server_stop
@@ -62,17 +58,21 @@ module Gitlab
         Settings.monitoring.sidekiq_exporter
       end
 
+      private
+
+      attr_reader :thread, :server
+
       def server_start
         return unless @server.nil?
 
         @server = ::WEBrick::HTTPServer.new(Port: settings.port, BindAddress: settings.address)
-        @server.mount "/", Rack::Handler::WEBrick, rack_app
+        server.mount "/", Rack::Handler::WEBrick, rack_app
 
-        @server.start
+        server.start
       end
 
       def server_stop
-        @server&.shutdown
+        server&.shutdown
         @server = nil
       end
 
diff --git a/spec/lib/gitlab/metrics/sidekiq_metrics_exporter_spec.rb b/spec/lib/gitlab/metrics/sidekiq_metrics_exporter_spec.rb
new file mode 100644
index 00000000000..bcf53febcac
--- /dev/null
+++ b/spec/lib/gitlab/metrics/sidekiq_metrics_exporter_spec.rb
@@ -0,0 +1,114 @@
+require 'spec_helper'
+
+describe Gitlab::Metrics::SidekiqMetricsExporter do
+  let(:exporter) { described_class.new }
+  let(:server) { double('server') }
+
+  before do
+    allow(::WEBrick::HTTPServer).to receive(:new).and_return(server)
+    allow(server).to receive(:mount)
+    allow(server).to receive(:start)
+    allow(server).to receive(:shutdown)
+  end
+
+  describe '.instance' do
+    it 'provides instance of SidekiQMetricsExporter' do
+      expect(described_class.instance).to be_instance_of(described_class)
+    end
+
+    it 'subsequent invocations provide the same instance' do
+      expect(described_class.instance).to eq(described_class.instance)
+    end
+
+    it 'is synchronized using mutex' do
+      expect(described_class::MUTEX).to receive(:synchronize)
+
+      described_class.instance
+    end
+
+    it 'creates at_exit hook when instance is created' do
+      described_class.instance_variable_set(:@instance, nil)
+      expect(Kernel).to receive(:at_exit)
+
+      expect(described_class.instance).not_to be_nil
+    end
+  end
+
+  describe 'when exporter is enabled' do
+    before do
+      allow(Settings.monitoring.sidekiq_exporter).to receive(:enabled).and_return(true)
+    end
+
+    describe 'when exporter is stopped' do
+      describe '#start' do
+        it 'starts the exporter' do
+          expect { exporter.start.join }.to change { exporter.running? }.from(false).to(true)
+
+          expect(server).to have_received(:start)
+        end
+
+        it 'starts server with port and address from settings' do
+          expect(::WEBrick::HTTPServer).to receive(:new).with(
+            Port: Settings.monitoring.sidekiq_exporter.port,
+            BindAddress: Settings.monitoring.sidekiq_exporter.address
+          )
+
+          exporter.start.join
+        end
+      end
+
+      describe '#stop' do
+        it "doesn't shutdown stopped server" do
+          expect { exporter.stop }.not_to change { exporter.running? }
+
+          expect(server).not_to have_received(:shutdown)
+        end
+      end
+    end
+
+    describe 'when exporter is running' do
+      before do
+        exporter.start.join
+      end
+
+      describe '#start' do
+        it "doesn't start running server" do
+          expect(server).to have_received(:start).once
+
+          expect { exporter.start.join }.not_to change { exporter.running? }
+        end
+      end
+
+      describe '#stop' do
+        it 'shutdowns server' do
+          expect { exporter.stop }.to change { exporter.running? }.from(true).to(false)
+
+          expect(server).to have_received(:shutdown)
+        end
+      end
+    end
+  end
+
+  describe 'when exporter is disabled' do
+    before do
+      allow(Settings.monitoring.sidekiq_exporter).to receive(:enabled).and_return(false)
+    end
+
+    describe '#start' do
+      it "doesn't start" do
+        expect(exporter.start).to be_nil
+        expect { exporter.start }.not_to change { exporter.running? }
+
+        expect(server).not_to have_received(:start)
+      end
+    end
+
+    describe '#stop' do
+      it "doesn't shutdown" do
+        expect { exporter.stop }.not_to change { exporter.running? }
+
+        expect(server).not_to have_received(:shutdown)
+      end
+    end
+  end
+end