Merge branch 'allow-address-in-use-for-sidekiq-exporter' into 'master'

Allow sidekiq_exporter to fail on address in use

Closes gitlab-com/gl-infra/infrastructure#8194

See merge request gitlab-org/gitlab!18725

lib/gitlab/metrics/exporter/sidekiq_exporter.rb

@@ -14,6 +14,29 @@ module Gitlab
         def log_filename
           File.join(Rails.root, 'log', 'sidekiq_exporter.log')
         end
+
+        private
+
+        # Sidekiq Exporter does not work properly in sidekiq-cluster
+        # mode. It tries to start the service on the same port for
+        # each of the cluster workers, this results in failure
+        # due to duplicate binding.
+        #
+        # For now we ignore this error, as metrics are still "kind of"
+        # valid as they are rendered from shared directory.
+        #
+        # Issue: https://gitlab.com/gitlab-org/gitlab/issues/5714
+        def start_working
+          super
+        rescue Errno::EADDRINUSE => e
+          Sidekiq.logger.error(
+            class: self.class.to_s,
+            message: 'Cannot start sidekiq_exporter',
+            exception: e.message
+          )
+
+          false
+        end
       end
     end
   end

spec/lib/gitlab/metrics/exporter/sidekiq_exporter_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe Gitlab::Metrics::Exporter::SidekiqExporter do
+  let(:exporter) { described_class.new }
+
+  after do
+    exporter.stop
+  end
+
+  context 'with valid config' do
+    before do
+      stub_config(
+        monitoring: {
+          sidekiq_exporter: {
+            enabled: true,
+            port: 0,
+            address: '127.0.0.1'
+          }
+        }
+      )
+    end
+
+    it 'does start thread' do
+      expect(exporter.start).not_to be_nil
+    end
+  end
+
+  context 'when port is already taken' do
+    let(:first_exporter) { described_class.new }
+
+    before do
+      stub_config(
+        monitoring: {
+          sidekiq_exporter: {
+            enabled: true,
+            port: 9992,
+            address: '127.0.0.1'
+          }
+        }
+      )
+
+      first_exporter.start
+    end
+
+    after do
+      first_exporter.stop
+    end
+
+    it 'does print error message' do
+      expect(Sidekiq.logger).to receive(:error)
+        .with(
+          class: described_class.to_s,
+          message: 'Cannot start sidekiq_exporter',
+          exception: anything)
+
+      exporter.start
+    end
+
+    it 'does not start thread' do
+      expect(exporter.start).to be_nil
+    end
+  end
+end