opt-out flag for automatic web instrumentation

Author: jcolbyfisher

README.md

@@ -44,6 +44,7 @@ After requiring the main file, you can further configure with:
 | client_custom_labels | A hash of custom labels to send with each client request | `{}` | None |
 | client_max_queue_size | The max amount of metrics to send before flushing | `10000` | `ENV['PROMETHEUS_CLIENT_MAX_QUEUE_SIZE']` |
 | client_thread_sleep | How often to sleep the worker thread that manages the client buffer (seconds) | `0.5` | `ENV['PROMETHEUS_CLIENT_THREAD_SLEEP']` |
+| disable_web_automatic_instrumentation | Opt out flag for Web instrumentation; use `Bigcommerce::Prometheus::Instrumentors::Web.new(app: Rails.application).start` in your app's code to start it up yourself  | `0` | `ENV['PROMETHEUS_WEB_DISABLE_AUTOMATIC_INSTRUMENTATION']` |
 | puma_collection_frequency | How often to poll puma collection metrics (seconds) | `30` | `ENV['PROMETHEUS_PUMA_COLLECTION_FREQUENCY']` |
 | server_host | The host to run the exporter on | `"0.0.0.0"` | `ENV['PROMETHEUS_SERVER_HOST']` |
 | server_port | The port to run the exporter on | `9394` | `ENV['PROMETHEUS_SERVER_PORT']` |

lib/bigcommerce/prometheus/configuration.rb

@@ -51,7 +51,10 @@ module Configuration
         resque_collectors: [],
         resque_type_collectors: [],
         web_collectors: [],
-        web_type_collectors: []
+        web_type_collectors: [],
+
+        # Additional configuration
+        web_disable_automatic_instrumentation: ENV.fetch('PROMETHEUS_WEB_DISABLE_AUTOMATIC_INSTRUMENTATION', 0).to_i.positive?
       }.freeze
 
       attr_accessor *VALID_CONFIG_KEYS.keys

lib/bigcommerce/prometheus/integrations/railtie.rb

@@ -23,7 +23,7 @@ module Integrations
       #
       class Railtie < ::Rails::Railtie
         initializer 'zzz.bc_prometheus_ruby.configure_rails_initialization' do |app|
-          Bigcommerce::Prometheus::Instrumentors::Web.new(app: app).start
+          Bigcommerce::Prometheus::Instrumentors::Web.new(app: app).start unless ::Bigcommerce::Prometheus.web_disable_automatic_instrumentation
         end
       end
     end