1 files changed, 116 insertions, 0 deletions
diff --git a/spec/initializers/memory_watchdog_spec.rb b/spec/initializers/memory_watchdog_spec.rb
new file mode 100644
index 00000000000..56f995b5cd3
--- /dev/null
+++ b/spec/initializers/memory_watchdog_spec.rb
@@ -0,0 +1,116 @@
+# frozen_string_literal: true
+
+require 'fast_spec_helper'
+
+RSpec.describe 'memory watchdog' do
+  subject(:run_initializer) do
+    load Rails.root.join('config/initializers/memory_watchdog.rb')
+  end
+
+  context 'when GITLAB_MEMORY_WATCHDOG_ENABLED is truthy' do
+    let(:env_switch) { 'true' }
+
+    before do
+      stub_env('GITLAB_MEMORY_WATCHDOG_ENABLED', env_switch)
+    end
+
+    context 'when runtime is an application' do
+      let(:watchdog) { instance_double(Gitlab::Memory::Watchdog) }
+      let(:background_task) { instance_double(Gitlab::BackgroundTask) }
+
+      before do
+        allow(Gitlab::Runtime).to receive(:application?).and_return(true)
+      end
+
+      it 'registers a life-cycle hook' do
+        expect(Gitlab::Cluster::LifecycleEvents).to receive(:on_worker_start)
+
+        run_initializer
+      end
+
+      shared_examples 'starts watchdog with handler' do |handler_class|
+        it "uses the #{handler_class} and starts the watchdog" do
+          expect(Gitlab::Memory::Watchdog).to receive(:new).with(
+            handler: an_instance_of(handler_class),
+            logger: Gitlab::AppLogger).and_return(watchdog)
+          expect(Gitlab::BackgroundTask).to receive(:new).with(watchdog).and_return(background_task)
+          expect(background_task).to receive(:start)
+          expect(Gitlab::Cluster::LifecycleEvents).to receive(:on_worker_start).and_yield
+
+          run_initializer
+        end
+      end
+
+      # In tests, the Puma constant does not exist so we cannot use a verified double.
+      # rubocop: disable RSpec/VerifiedDoubles
+      context 'when puma' do
+        let(:puma) do
+          Class.new do
+            def self.cli_config
+              Struct.new(:options).new
+            end
+          end
+        end
+
+        before do
+          stub_const('Puma', puma)
+          stub_const('Puma::Cluster::WorkerHandle', double.as_null_object)
+
+          allow(Gitlab::Runtime).to receive(:puma?).and_return(true)
+        end
+
+        it_behaves_like 'starts watchdog with handler', Gitlab::Memory::Watchdog::PumaHandler
+      end
+      # rubocop: enable RSpec/VerifiedDoubles
+
+      context 'when sidekiq' do
+        before do
+          allow(Gitlab::Runtime).to receive(:sidekiq?).and_return(true)
+        end
+
+        it_behaves_like 'starts watchdog with handler', Gitlab::Memory::Watchdog::TermProcessHandler
+      end
+
+      context 'when other runtime' do
+        it_behaves_like 'starts watchdog with handler', Gitlab::Memory::Watchdog::NullHandler
+      end
+    end
+
+    context 'when runtime is unsupported' do
+      it 'does not register life-cycle hook' do
+        expect(Gitlab::Cluster::LifecycleEvents).not_to receive(:on_worker_start)
+
+        run_initializer
+      end
+    end
+  end
+
+  context 'when GITLAB_MEMORY_WATCHDOG_ENABLED is false' do
+    let(:env_switch) { 'false' }
+
+    before do
+      stub_env('GITLAB_MEMORY_WATCHDOG_ENABLED', env_switch)
+      # To rule out we return early due to this being false.
+      allow(Gitlab::Runtime).to receive(:application?).and_return(true)
+    end
+
+    it 'does not register life-cycle hook' do
+      expect(Gitlab::Cluster::LifecycleEvents).not_to receive(:on_worker_start)
+
+      run_initializer
+    end
+  end
+
+  context 'when GITLAB_MEMORY_WATCHDOG_ENABLED is not set' do
+    before do
+      # To rule out we return early due to this being false.
+      allow(Gitlab::Runtime).to receive(:application?).and_return(true)
+    end
+
+    it 'does not register life-cycle hook' do
+      expect(Gitlab::Cluster::LifecycleEvents).not_to receive(:on_worker_start)
+
+      run_initializer
+    end
+  end
+end