Allow setting statsd_client to automatically configure StatsdListener

CHANGELOG.md

@@ -2,7 +2,6 @@
 
 ## [0.1.4] - 2025-01-14
 
-- Support instrumentation via event hook approach
 - Support metrics logging via StatsdListener
 
 ## [0.1.3] - 2025-01-14

README.md

@@ -28,7 +28,14 @@ Idempotency.configure do |config|
   }
 
   config.idempotent_methods = %w[POST PUT PATCH]
-  config.idempotent_statuses = (200..299).to_a
+  config.idempotent_statuses = (200..299).to_a + (400..499).to_a
+
+  # Metrics configuration
+  config.metrics.statsd_client = statsd_client # Your StatsD client instance
+  config.metrics.namespace = 'my_service_name' # Optional namespace for metrics
+
+  # Custom instrumentation listeners (optional)
+  config.instrumentation_listeners = [my_custom_listener] # Array of custom listeners
 end
 ```
 
@@ -102,7 +109,7 @@ end
 
 ### Instrumentation
 
-The gem supports instrumentation through StatsD. It tracks the following metrics:
+The gem supports instrumentation through StatsD out of the box. When you configure a StatsD client in the configuration, the StatsdListener will be automatically set up. It tracks the following metrics:
 
 - `idempotency_cache_hit_count` - Incremented when a cached response is found
 - `idempotency_cache_miss_count` - Incremented when no cached response exists
@@ -114,17 +121,11 @@ Each metric includes tags:
 - `namespace` - Your configured namespace (if provided)
 - `metric` - The metric name (for duration histogram only)
 
-To enable above instrumentation, configure a StatsD listener:
+To enable StatsD instrumentation, simply configure the metrics settings:
 
 ```ruby
-statsd_client = Datadog::Statsd.new
-statsd_listener = Idempotency::Instrumentation::StatsdListener.new(
-  statsd_client,
-  'my_service_name'
-)
-
 Idempotency.configure do |config|
-  config.instrumentation_listeners = [statsd_listener]
+  config.metrics.statsd_client = Datadog::Statsd.new
+  config.metrics.namespace = 'my_service_name'
 end
 ```
-

lib/idempotency.rb

@@ -23,6 +23,10 @@ def self.notifier
   setting :redis_pool
   setting :logger
   setting :instrumentation_listeners, default: []
+  setting :metrics do
+    setting :namespace
+    setting :statsd_client
+  end
 
   setting :default_lock_expiry, default: 300 # 5 minutes
   setting :idempotent_methods, default: %w[POST PUT PATCH DELETE]
@@ -37,6 +41,13 @@ def self.notifier
   def self.configure
     super
 
+    if config.metrics.statsd_client
+      config.instrumentation_listeners << Idempotency::Instrumentation::StatsdListener.new(
+        config.metrics.statsd_client,
+        config.metrics.namespace
+      )
+    end
+
     config.instrumentation_listeners.each(&:setup_subscriptions)
   end
 

spec/idempotency_spec.rb

@@ -156,4 +156,42 @@
     expect(config.default_lock_expiry).to eq(60)
     expect(config.response_body.concurrent_error).to eq({ errors: [{ code: 'GH0004', message: 'Some message' }] })
   end
+
+  describe '#configure' do
+    let(:statsd_client) { double('statsd_client') }
+    let(:custom_listener) { double('custom_listener', setup_subscriptions: true) }
+
+    before do
+      described_class.config.metrics.statsd_client = nil
+      described_class.config.instrumentation_listeners = []
+    end
+
+    it 'sets up StatsdListener when statsd_client is configured' do
+      expect(Idempotency::Instrumentation::StatsdListener).to receive(:new)
+        .with(statsd_client, 'test_namespace')
+        .and_return(custom_listener)
+
+      described_class.configure do |config|
+        config.metrics.statsd_client = statsd_client
+        config.metrics.namespace = 'test_namespace'
+      end
+
+      expect(described_class.config.instrumentation_listeners).to include(custom_listener)
+    end
+
+    it 'calls setup_subscriptions on all listeners' do
+      described_class.config.instrumentation_listeners = [custom_listener]
+      expect(custom_listener).to receive(:setup_subscriptions)
+
+      described_class.configure
+    end
+
+    it 'does not add StatsdListener when statsd_client is not configured' do
+      described_class.configure do |config|
+        config.metrics.namespace = 'test_namespace'
+      end
+
+      expect(described_class.config.instrumentation_listeners).to be_empty
+    end
+  end
 end