From 055faac14f8482581adf3d6ef58b5e6b2984cc09 Mon Sep 17 00:00:00 2001
From: Eugene Burmakin <iamfrey@gmail.com>
Date: Wed, 20 Nov 2024 12:02:31 +0100
Subject: [PATCH] Add prometheus_exporter gem and instrumentation to the
 project

---
 Gemfile                           |  1 +
 Gemfile.lock                      |  4 ++++
 config/initializers/prometheus.rb | 15 +++++++++++++++
 config/initializers/sidekiq.rb    |  5 +++++
 config/puma.rb                    |  6 ++++++
 5 files changed, 31 insertions(+)
 create mode 100644 config/initializers/prometheus.rb

diff --git a/Gemfile b/Gemfile
index 45a72399..d831ec9d 100644
--- a/Gemfile
+++ b/Gemfile
@@ -6,6 +6,7 @@ git_source(:github) { |repo| "https://github.com/#{repo}.git" }
 ruby File.read('.ruby-version').strip
 
 gem 'bootsnap', require: false
+gem 'prometheus_exporter'
 gem 'chartkick'
 gem 'data_migrate'
 gem 'devise'
diff --git a/Gemfile.lock b/Gemfile.lock
index 091c2c14..551e0ff4 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -233,6 +233,8 @@ GEM
     patience_diff (1.2.0)
       optimist (~> 3.0)
     pg (1.5.9)
+    prometheus_exporter (2.1.1)
+      webrick
     pry (0.14.2)
       coderay (~> 1.1)
       method_source (~> 1.0)
@@ -408,6 +410,7 @@ GEM
       addressable (>= 2.8.0)
       crack (>= 0.3.2)
       hashdiff (>= 0.4.0, < 2.0.0)
+    webrick (1.9.0)
     websocket-driver (0.7.6)
       websocket-extensions (>= 0.1.0)
     websocket-extensions (0.1.5)
@@ -441,6 +444,7 @@ DEPENDENCIES
   lograge
   oj
   pg
+  prometheus_exporter
   pry-byebug
   pry-rails
   puma
diff --git a/config/initializers/prometheus.rb b/config/initializers/prometheus.rb
new file mode 100644
index 00000000..9d25d4ea
--- /dev/null
+++ b/config/initializers/prometheus.rb
@@ -0,0 +1,15 @@
+# in config/initializers/prometheus.rb
+if Rails.env != "test"
+  require 'prometheus_exporter/middleware'
+
+  # This reports stats per request like HTTP status and timings
+  Rails.application.middleware.unshift PrometheusExporter::Middleware
+end
+
+if Rails.env != "test"
+  require 'prometheus_exporter/instrumentation'
+
+  # this reports basic process stats like RSS and GC info, type master
+  # means it is instrumenting the master process
+  PrometheusExporter::Instrumentation::Process.start(type: "master")
+end
diff --git a/config/initializers/sidekiq.rb b/config/initializers/sidekiq.rb
index 3d2e4741..d3c9bbea 100644
--- a/config/initializers/sidekiq.rb
+++ b/config/initializers/sidekiq.rb
@@ -2,6 +2,11 @@
 
 Sidekiq.configure_server do |config|
   config.redis = { url: ENV['REDIS_URL'] }
+
+  config.server_middleware do |chain|
+    require 'prometheus_exporter/instrumentation'
+    chain.add PrometheusExporter::Instrumentation::Sidekiq
+ end
 end
 
 Sidekiq.configure_client do |config|
diff --git a/config/puma.rb b/config/puma.rb
index daaf0369..08673ab4 100644
--- a/config/puma.rb
+++ b/config/puma.rb
@@ -41,3 +41,9 @@ pidfile ENV.fetch("PIDFILE") { "tmp/pids/server.pid" }
 
 # Allow puma to be restarted by `bin/rails restart` command.
 plugin :tmp_restart
+
+# in unicorn/puma/passenger be sure to run a new process instrumenter after fork
+after_worker_boot do
+  require 'prometheus_exporter/instrumentation'
+  PrometheusExporter::Instrumentation::Process.start(type:"web")
+end