fix: compact Dalli attributes

Author: nickamorim

instrumentation/dalli/lib/opentelemetry/instrumentation/dalli/patches/server.rb

@@ -17,7 +17,7 @@ def request(op, *args) # rubocop:disable Naming/MethodParameterName
               'db.operation' => operation,
               'net.peer.name' => hostname,
               'net.peer.port' => port
-            }
+            }.compact
             if config[:db_statement] == :include
               attributes['db.statement'] = Utils.format_command(operation, args)
             elsif config[:db_statement] == :obfuscate

instrumentation/dalli/test/opentelemetry/instrumentation/dalli/instrumentation_test.rb

@@ -44,6 +44,22 @@
         _(span.attributes['peer.service']).must_equal 'readonly:memcached'
       end
 
+      it 'supports unix domain socket' do
+        dalli.version
+
+        server = dalli.instance_variable_get(:@ring).servers.first
+        server.stub(:hostname, '/tmp/memcached.sock') do
+          server.stub(:port, nil) do
+            dalli.set('foo', 'bar')
+
+            _(exporter.finished_spans.size).must_equal 1
+            _(span.name).must_equal 'set'
+            _(span.attributes).wont_include 'net.peer.port'
+            _(span.attributes['net.peer.name']).must_equal '/tmp/memcached.sock'
+          end
+        end
+      end
+
       it 'before request' do
         _(exporter.finished_spans.size).must_equal 0
       end