Update Prometheus Client MMAP gem to version that fixes performance...

Update Prometheus Client MMAP gem to version that fixes performance degradation caused by workers churn

Gemfile

@@ -284,7 +284,7 @@ group :metrics do
   gem 'influxdb', '~> 0.2', require: false
   # Prometheus
-  gem 'prometheus-client-mmap', '~>0.7.0.beta12'
+  gem 'prometheus-client-mmap', '~>0.7.0.beta14'
   gem 'raindrops', '~> 0.18'
 end

Gemfile.lock

@@ -619,7 +619,7 @@ GEM
       parser
       unparser
     procto (0.0.3)
-    prometheus-client-mmap (0.7.0.beta12)
+    prometheus-client-mmap (0.7.0.beta14)
       mmap2 (~> 2.2, >= 2.2.7)
     pry (0.10.4)
       coderay (~> 1.1.0)
@@ -1093,7 +1093,7 @@ DEPENDENCIES
   pg (~> 0.18.2)
   poltergeist (~> 1.9.0)
   premailer-rails (~> 1.9.7)
-  prometheus-client-mmap (~> 0.7.0.beta12)
+  prometheus-client-mmap (~> 0.7.0.beta14)
   pry-byebug (~> 3.4.1)
   pry-rails (~> 0.3.4)
   rack-attack (~> 4.4.1)

config/initializers/7_prometheus_metrics.rb

 require 'prometheus/client'
+require 'prometheus/client/support/unicorn'
 Prometheus::Client.configure do |config|
   config.logger = Rails.logger
@@ -9,6 +10,8 @@ Prometheus::Client.configure do |config|
   if Rails.env.development? || Rails.env.test?
     config.multiprocess_files_dir ||= Rails.root.join('tmp/prometheus_multiproc_dir')
   end
+
+  config.pid_provider = Prometheus::Client::Support::Unicorn.method(:worker_pid_provider)
 end
 Sidekiq.configure_server do |config|