support tagging for appsignal metric

Author: Vuta

Diff for: README.md

@@ -104,6 +104,23 @@ EventTracer.info action: 'Action', message: 'Message', appsignal: { increment_co
 #  counter_2, 2
 ```
 
+We can also add [tags](https://docs.appsignal.com/metrics/custom.html#metric-tags) for metric
+
+```ruby
+# Sample usage
+EventTracer.info(
+  action: 'Action',
+  message: 'Message',
+  appsignal: {
+    increment_counter: {
+      counter_1: { value: 1, tags: { region: 'eu' } }
+    }
+  }
+)
+# This calls .increment_counter on Appsignal once with additional tag
+# counter_1, 1, region: 'eu'
+```
+
 **Summary**
 
 In all the generated interface for `EventTracer` logging could look something like this

Diff for: lib/event_tracer/appsignal_logger.rb

@@ -7,6 +7,7 @@
 #
 # Usage: EventTracer.register :appsignal, EventTracer::AppsignalLogger.new(Appsignal)
 #        appsignal_logger.info appsignal: { increment_counter: { counter_1: 1, counter_2: 2 }, set_gauge: { gauge_1: 1 } }
+#        appsignal_logger.info appsignal: { set_gauge: { gauge_1: { value: 1, region: 'eu' } } }
 module EventTracer
   class AppsignalLogger < BasicDecorator
 
@@ -21,6 +22,8 @@ class AppsignalLogger < BasicDecorator
           return LogResult.new(false, "Appsignal metric #{metric} invalid") unless metric_args && metric_args.is_a?(Hash) 
 
           send_metric metric, metric_args
+        rescue Exception => e
+          return LogResult.new(false, e.message)
         end
 
         LogResult.new(true)
@@ -37,10 +40,22 @@ def applied_metrics(appsignal_args)
       end
 
       def send_metric(metric, payload)
-        payload.each do |increment, value|
-          appsignal.send(metric, increment, value)
+        payload.each do |increment, attribute|
+          if attribute.is_a?(Hash)
+            begin
+              appsignal.send(
+                metric,
+                increment,
+                attribute.fetch(:value),
+                attribute.fetch(:tags)
+              )
+            rescue KeyError
+              raise Exception, "Appsignal payload { #{increment}: #{attribute} } invalid"
+            end
+          else
+            appsignal.send(metric, increment, attribute)
+          end
         end
       end
-
   end
 end

Diff for: spec/event_tracer/appsignal_logger_spec.rb

@@ -51,17 +51,26 @@
   end
 
   shared_examples_for 'processes_hashed_inputs' do
-    let(:appsignal_payload) { {
-      increment_counter: { 'Counter_1' => 1, 'Counter_2' => 2 },
-      add_distribution_value: { 'Distribution_1' => 10 },
-      set_gauge: { 'Gauge_1' => 100 }
-    } }
+    let(:appsignal_payload) do
+      {
+        increment_counter: {
+          'Counter_1' => { value: 1, tags: { tag_a: 'a', tag_b: 'b' } },
+          'Counter_2' => 2
+        },
+        add_distribution_value: { 'Distribution_1' => 10 },
+        set_gauge: {
+          'Gauge_1' => 100,
+          'Gauge_2' => { value: 200, tags: { region: 'eu' } }
+        }
+      }
+    end
 
     it 'processes each hash keyset as a metric iteration' do
-      expect(mock_appsignal).to receive(:increment_counter).with('Counter_1', 1)
+      expect(mock_appsignal).to receive(:increment_counter).with('Counter_1', 1, tag_a: 'a', tag_b: 'b')
       expect(mock_appsignal).to receive(:increment_counter).with('Counter_2', 2)
       expect(mock_appsignal).to receive(:add_distribution_value).with('Distribution_1', 10)
       expect(mock_appsignal).to receive(:set_gauge).with('Gauge_1', 100)
+      expect(mock_appsignal).to receive(:set_gauge).with('Gauge_2', 200, region: 'eu')
 
       result = subject.send(expected_call, appsignal: appsignal_payload)
 
@@ -88,6 +97,27 @@
           end
         end
       end
+
+      context 'with invalid tagging payload' do
+        let(:appsignal_payload) do
+          {
+            metric => {
+              'Counter_1' => { value: 1, tag: { tag_a: 'a' } }
+            }
+          }
+        end
+
+        it 'rejects the payload and return failure result' do
+          expect(mock_appsignal).not_to receive(:increment_counter)
+          expect(mock_appsignal).not_to receive(:add_distribution_value)
+          expect(mock_appsignal).not_to receive(:set_gauge)
+
+          result = subject.send(expected_call, appsignal: appsignal_payload)
+
+          expect(result.success?).to eq false
+          expect(result.error).to eq "Appsignal payload { Counter_1: {:value=>1, :tag=>{:tag_a=>\"a\"}} } invalid"
+        end
+      end
     end
   end