1 files changed, 84 insertions, 0 deletions
diff --git a/spec/lib/gitlab/metrics/boot_time_tracker_spec.rb b/spec/lib/gitlab/metrics/boot_time_tracker_spec.rb
new file mode 100644
index 00000000000..8a17fa8dd2e
--- /dev/null
+++ b/spec/lib/gitlab/metrics/boot_time_tracker_spec.rb
@@ -0,0 +1,84 @@
+# frozen_string_literal: true
+
+require 'fast_spec_helper'
+
+RSpec.describe Gitlab::Metrics::BootTimeTracker do
+  let(:logger) { double('logger') }
+  let(:gauge) { double('gauge') }
+
+  subject(:tracker) { described_class.instance }
+
+  before do
+    described_class.instance.reset!
+
+    allow(logger).to receive(:info)
+    allow(gauge).to receive(:set)
+    allow(Gitlab::Metrics).to receive(:gauge).and_return(gauge)
+  end
+
+  describe '#track_boot_time!' do
+    described_class::SUPPORTED_RUNTIMES.each do |runtime|
+      context "when called on #{runtime} for the first time" do
+        before do
+          expect(Gitlab::Runtime).to receive(:safe_identify).and_return(runtime)
+        end
+
+        it 'set the startup_time' do
+          tracker.track_boot_time!(logger: logger)
+
+          expect(tracker.startup_time).to be > 0
+        end
+
+        it 'records the current process runtime' do
+          expect(Gitlab::Metrics::System).to receive(:process_runtime_elapsed_seconds).once
+
+          tracker.track_boot_time!(logger: logger)
+        end
+
+        it 'logs the application boot time' do
+          expect(Gitlab::Metrics::System).to receive(:process_runtime_elapsed_seconds).and_return(42)
+          expect(logger).to receive(:info).with(message: 'Application boot finished', runtime: runtime.to_s, duration_s: 42)
+
+          tracker.track_boot_time!(logger: logger)
+        end
+
+        it 'tracks boot time in a prometheus gauge' do
+          expect(Gitlab::Metrics::System).to receive(:process_runtime_elapsed_seconds).and_return(42)
+          expect(gauge).to receive(:set).with({}, 42)
+
+          tracker.track_boot_time!(logger: logger)
+        end
+
+        context 'on subsequent calls' do
+          it 'does nothing' do
+            tracker.track_boot_time!(logger: logger)
+
+            expect(Gitlab::Metrics::System).not_to receive(:process_runtime_elapsed_seconds)
+            expect(logger).not_to receive(:info)
+            expect(gauge).not_to receive(:set)
+
+            tracker.track_boot_time!(logger: logger)
+          end
+        end
+      end
+    end
+
+    context 'when called on other runtimes' do
+      it 'does nothing' do
+        tracker.track_boot_time!(logger: logger)
+
+        expect(Gitlab::Metrics::System).not_to receive(:process_runtime_elapsed_seconds)
+        expect(logger).not_to receive(:info)
+        expect(gauge).not_to receive(:set)
+
+        tracker.track_boot_time!(logger: logger)
+      end
+    end
+  end
+
+  describe '#startup_time' do
+    it 'returns 0 when boot time not tracked' do
+      expect(tracker.startup_time).to eq(0)
+    end
+  end
+end