Clean Sidekiq metrics from multiproc dir on start

After moving the multiproc dir cleanup into `config.ru`:`warmup`, we
stopped cleaning Sidekiq metrics dir which is not correct.
This MR intended to fix that. More details:
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/31668

1 files changed, 51 insertions, 0 deletions

diff --git a/spec/lib/prometheus/cleanup_multiproc_dir_service_spec.rb b/spec/lib/prometheus/cleanup_multiproc_dir_service_spec.rb
new file mode 100644
index 00000000000..c7302a1a656
--- /dev/null
+++ b/spec/lib/prometheus/cleanup_multiproc_dir_service_spec.rb
@@ -0,0 +1,51 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe Prometheus::CleanupMultiprocDirService do
+  describe '.call' do
+    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
+      FileUtils.touch(metrics_file_path)
+    end
+
+    after do
+      FileUtils.rm_r(metrics_multiproc_dir)
+    end
+
+    context 'when `multiprocess_files_dir` is defined' do
+      before do
+        expect(Prometheus::Client.configuration)
+              .to receive(:multiprocess_files_dir)
+              .and_return(metrics_multiproc_dir)
+              .at_least(:once)
+      end
+
+      it 'removes old metrics' do
+        expect { subject }
+          .to change { File.exist?(metrics_file_path) }
+          .from(true)
+          .to(false)
+      end
+    end
+
+    context 'when `multiprocess_files_dir` is not defined' do
+      before do
+        expect(Prometheus::Client.configuration)
+              .to receive(:multiprocess_files_dir)
+              .and_return(nil)
+              .at_least(:once)
+      end
+
+      it 'does not remove any files' do
+        expect { subject }
+          .not_to change { File.exist?(metrics_file_path) }
+          .from(true)
+      end
+    end
+  end
+end