Apply review suggestions65278-cleanup-sidekiq-metrics-dir-on-start

Use service class instead of static module methods, style fixes

5 files changed, 28 insertions, 18 deletions

diff --git a/config.ru b/config.ru
index 048eb0d8392..750c84f7642 100644
--- a/config.ru
+++ b/config.ru
@@ -26,7 +26,7 @@ warmup do |app|
   # It needs to be done as early as here to ensure metrics files aren't deleted.
   # After we hit our app in `warmup`, first metrics and corresponding files already being created,
   # for example in `lib/gitlab/metrics/requests_rack_middleware.rb`.
-  Prometheus::CleanupMultiprocDir.call if master_process?
+  Prometheus::CleanupMultiprocDirService.new.execute if master_process?
 
   client = Rack::MockRequest.new(app)
   client.get('/')
diff --git a/config/initializers/7_prometheus_metrics.rb b/config/initializers/7_prometheus_metrics.rb
index cc5100b692c..143b34b5368 100644
--- a/config/initializers/7_prometheus_metrics.rb
+++ b/config/initializers/7_prometheus_metrics.rb
@@ -33,7 +33,7 @@ end
 Sidekiq.configure_server do |config|
   config.on(:startup) do
     # webserver metrics are cleaned up in config.ru: `warmup` block
-    Prometheus::CleanupMultiprocDir.call if Prometheus::PidProvider.worker_id == 'sidekiq'
+    Prometheus::CleanupMultiprocDirService.new.execute
 
     Gitlab::Metrics::SidekiqMetricsExporter.instance.start
   end
diff --git a/lib/prometheus/cleanup_multiproc_dir.rb b/lib/prometheus/cleanup_multiproc_dir.rb
deleted file mode 100644
index 6605455c528..00000000000
--- a/lib/prometheus/cleanup_multiproc_dir.rb
+++ /dev/null
@@ -1,13 +0,0 @@
-# frozen_string_literal: true
-
-module Prometheus
-  module CleanupMultiprocDir
-    def self.call
-      if dir = ::Prometheus::Client.configuration.multiprocess_files_dir
-        old_metrics = Dir[File.join(dir, '*.db')]
-
-        FileUtils.rm_rf(old_metrics)
-      end
-    end
-  end
-end
diff --git a/lib/prometheus/cleanup_multiproc_dir_service.rb b/lib/prometheus/cleanup_multiproc_dir_service.rb
new file mode 100644
index 00000000000..6418b4de166
--- /dev/null
+++ b/lib/prometheus/cleanup_multiproc_dir_service.rb
@@ -0,0 +1,23 @@
+# frozen_string_literal: true
+
+module Prometheus
+  class CleanupMultiprocDirService
+    include Gitlab::Utils::StrongMemoize
+
+    def execute
+      FileUtils.rm_rf(old_metrics) if old_metrics
+    end
+
+    private
+
+    def old_metrics
+      strong_memoize(:old_metrics) do
+        Dir[File.join(multiprocess_files_dir, '*.db')] if multiprocess_files_dir
+      end
+    end
+
+    def multiprocess_files_dir
+      ::Prometheus::Client.configuration.multiprocess_files_dir
+    end
+  end
+end
diff --git a/spec/lib/prometheus/cleanup_multiproc_dir_spec.rb b/spec/lib/prometheus/cleanup_multiproc_dir_service_spec.rb
index 8b694bb71cf..c7302a1a656 100644
--- a/spec/lib/prometheus/cleanup_multiproc_dir_spec.rb
+++ b/spec/lib/prometheus/cleanup_multiproc_dir_service_spec.rb
@@ -2,15 +2,15 @@
 
 require 'spec_helper'
 
-describe Prometheus::CleanupMultiprocDir do
+describe Prometheus::CleanupMultiprocDirService do
   describe '.call' do
-    subject { described_class.call }
+    subject { described_class.new.execute }
 
     let(:metrics_multiproc_dir) { Dir.mktmpdir }
     let(:metrics_file_path) { File.join(metrics_multiproc_dir, 'counter_puma_master-0.db') }
 
     before do
-      File.new(metrics_file_path, 'w+')
+      FileUtils.touch(metrics_file_path)
     end
 
     after do