Reinitialize metric files on master start

Gemfile

@@ -326,7 +326,7 @@ group :metrics do
   gem 'influxdb', '~> 0.2', require: false
 
   # Prometheus
-  gem 'prometheus-client-mmap', '~> 0.9.9'
+  gem 'prometheus-client-mmap', '~> 0.9.10'
   gem 'raindrops', '~> 0.18'
 end
 

Gemfile.lock

@@ -715,7 +715,7 @@ GEM
       parser
       unparser
     procto (0.0.3)
-    prometheus-client-mmap (0.9.9)
+    prometheus-client-mmap (0.9.10)
     pry (0.11.3)
       coderay (~> 1.1.0)
       method_source (~> 0.9.0)
@@ -1250,7 +1250,7 @@ DEPENDENCIES
   org-ruby (~> 0.9.12)
   pg (~> 1.1)
   premailer-rails (~> 1.9.7)
-  prometheus-client-mmap (~> 0.9.9)
+  prometheus-client-mmap (~> 0.9.10)
   pry-byebug (~> 3.5.1)
   pry-rails (~> 0.3.4)
   puma (~> 3.12)

config/initializers/7_prometheus_metrics.rb

@@ -47,10 +47,12 @@ if !Rails.env.test? && Gitlab::Metrics.prometheus_metrics_enabled?
   end
 
   Gitlab::Cluster::LifecycleEvents.on_master_start do
+    ::Prometheus::Client.reinitialize_on_pid_change(force: true)
+
     if defined?(::Unicorn)
-      Gitlab::Metrics::Samplers::UnicornSampler.initialize_instance(Settings.monitoring.unicorn_sampler_interval).start
+      Gitlab::Metrics::Samplers::UnicornSampler.instance(Settings.monitoring.unicorn_sampler_interval).start
     elsif defined?(::Puma)
-      Gitlab::Metrics::Samplers::PumaSampler.initialize_instance(Settings.monitoring.puma_sampler_interval).start
+      Gitlab::Metrics::Samplers::PumaSampler.instance(Settings.monitoring.puma_sampler_interval).start
     end
   end
 end

ee/changelogs/unreleased/66889-reset-and-reinitialize-prometheus-client-on-master-start.yml

+---
+title: Reinitialize metrics files on webserver master process start
+merge_request: 16623
+author:
+type: fixed

lib/gitlab/daemon.rb

@@ -10,8 +10,8 @@ module Gitlab
       @instance
     end
 
-    def self.instance
-      @instance ||= initialize_instance
+    def self.instance(*args)
+      @instance ||= initialize_instance(*args)
     end
 
     attr_reader :thread