Setup Prometheus & Grafana

.dev_to/compose.yml

@@ -46,6 +46,7 @@ x-backend: &backend
     IRB_HISTFILE: /usr/local/hist/.irb_history
     EDITOR: vi
     SKYLIGHT_AUTHENTICATION: $SKYLIGHT_AUTHENTICATION
+    PROMETHEUS_EXPORTER_HOST: exporter
   depends_on: &backend_depends_on
     postgres:
       condition: service_healthy
@@ -72,6 +73,12 @@ services:
   #   <<: *backend
   #   command: bundle exec sidekiq -C config/sidekiq.yml
 
+  exporter:
+    <<: *backend
+    command: bundle exec prometheus_exporter -b 0.0.0.0 -a prometheus/custom_collector.rb
+    ports:
+      - "9394:9394"
+
   postgres:
     image: postgres:14
     volumes:
@@ -99,6 +106,24 @@ services:
       timeout: 3s
       retries: 30
 
+  prometheus:
+    image: dockerhub.timeweb.cloud/prom/prometheus
+    volumes:
+      - ./prometheus.yml:/etc/prometheus/prometheus.yml
+      - prom_data:/prometheus
+    command:
+      - '--config.file=/etc/prometheus/prometheus.yml'
+    ports:
+      - '9090:9090'
+  grafana:
+    image: dockerhub.timeweb.cloud/grafana/grafana
+    environment:
+      - GF_SECURITY_ADMIN_PASSWORD=pass
+    depends_on:
+      - prometheus
+    ports:
+      - "3030:3000"
+
   webpacker:
     <<: *app
     command: bundle exec ./bin/webpack-dev-server
@@ -124,3 +149,4 @@ volumes:
   redis:
   packs:
   packs-test:
+  prom_data:

.dev_to/prometheus.yml

@@ -0,0 +1,11 @@
+global:
+  scrape_interval: 5s
+  external_labels:
+    monitor: 'my-monitor'
+scrape_configs:
+  - job_name: 'prometheus'
+    static_configs:
+      - targets: ['localhost:9090']
+  - job_name: 'devdev'
+    static_configs:
+      - targets: ['exporter:9394']

Gemfile

@@ -103,6 +103,7 @@ gem "validate_url", "~> 1.0"
 gem "webpacker", "~> 3.5"
 gem "webpush", "~> 0.3"
 gem "rack-mini-profiler"
+gem "prometheus_exporter"
 
 group :development do
   gem "better_errors", "~> 2.5"

Gemfile.lock

@@ -638,6 +638,8 @@ GEM
       ast (~> 2.4.0)
     pg (1.1.4)
     powerpack (0.1.2)
+    prometheus_exporter (2.1.0)
+      webrick
     pry (0.12.2)
       coderay (~> 1.1.0)
       method_source (~> 0.9.0)
@@ -917,6 +919,7 @@ GEM
     webpush (0.3.2)
       hkdf (~> 0.2)
       jwt
+    webrick (1.8.1)
     websocket-driver (0.6.5)
       websocket-extensions (>= 0.1.0)
     websocket-extensions (0.1.3)
@@ -1005,6 +1008,7 @@ DEPENDENCIES
   omniauth-twitter (~> 1.4)
   parallel_tests (~> 2.27)
   pg (~> 1.1)
+  prometheus_exporter
   pry (~> 0.12)
   pry-byebug (~> 3.7)
   pry-rails (~> 0.3)

config/initializers/prometheus.rb

@@ -0,0 +1,6 @@
+unless Rails.env.test?
+  require 'prometheus_exporter/middleware'
+
+  # This reports stats per request like HTTP status and timings
+  Rails.application.middleware.unshift PrometheusExporter::Middleware
+end

prometheus/custom_collector.rb

@@ -0,0 +1,15 @@
+class CustomCollector < PrometheusExporter::Server::TypeCollector
+  unless defined? Rails
+    require File.expand_path("../../config/environment", __FILE__)
+  end
+
+  def type
+    "mariela_posts"
+  end
+
+  def metrics
+    mariela_posts_gague = PrometheusExporter::Metric::Gauge.new('mariela_posts', 'number of mariela posts')
+    mariela_posts_gague.observe User.find_by_name('Mariela Ledner').articles.count
+    [mariela_posts_gague]
+  end
+end