Support Unix domain socket in Kafka::Datadog

dogstatsd-ruby has supported Unix domain socket.
cf. DataDog/dogstatsd-ruby#61

lib/kafka/datadog.rb

@@ -31,7 +31,7 @@ module Datadog
 
     class << self
       def statsd
-        @statsd ||= ::Datadog::Statsd.new(host, port, namespace: namespace, tags: tags)
+        @statsd ||= ::Datadog::Statsd.new(host, port, namespace: namespace, tags: tags, socket_path: socket_path)
       end
 
       def statsd=(statsd)
@@ -57,6 +57,15 @@ def port=(port)
         clear
       end
 
+      def socket_path
+        @socket_path
+      end
+
+      def socket_path=(socket_path)
+        @socket_path = socket_path
+        clear
+      end
+
       def namespace
         @namespace ||= STATSD_NAMESPACE
       end

spec/datadog_spec.rb

@@ -14,20 +14,40 @@
     agent.stop
   end
 
-  it "emits metrics to the Datadog agent" do
-    Kafka::Datadog.host = agent.host
-    Kafka::Datadog.port = agent.port
+  context "when host and port are specified" do
+    it "emits metrics to the Datadog agent" do
+      Kafka::Datadog.host = agent.host
+      Kafka::Datadog.port = agent.port
 
-    client = Kafka::Datadog.statsd
+      client = Kafka::Datadog.statsd
 
-    client.increment("greetings")
+      client.increment("greetings")
 
-    agent.wait_for_metrics
+      agent.wait_for_metrics
 
-    expect(agent.metrics.count).to eq 1
+      expect(agent.metrics.count).to eq 1
 
-    metric = agent.metrics.first
+      metric = agent.metrics.first
 
-    expect(metric).to eq "ruby_kafka.greetings"
+      expect(metric).to eq "ruby_kafka.greetings"
+    end
+  end
+
+  context "when socket_path is specified" do
+    it "emits metrics to the Datadog agent" do
+      Kafka::Datadog.socket_path = agent.socket_path
+
+      client = Kafka::Datadog.statsd
+
+      client.increment("greetings")
+
+      agent.wait_for_metrics
+
+      expect(agent.metrics.count).to eq 1
+
+      metric = agent.metrics.first
+
+      expect(metric).to eq "ruby_kafka.greetings"
+    end
   end
 end

spec/fake_datadog_agent.rb

@@ -1,27 +1,39 @@
 # frozen_string_literal: true
 
 require "socket"
+require "tempfile"
 
 class FakeDatadogAgent
-  attr_reader :host, :port, :metrics
+  attr_reader :host, :port, :socket_path, :metrics
 
   def initialize
     @host = "127.0.0.1"
     @port = 9999
-    @socket = UDPSocket.new
-    @thread = nil
+    @socket_path = Tempfile.open("fake_datadog_agent_sock") do |f|
+      path = f.path
+      f.unlink
+      path
+    end
+    @udp_socket = UDPSocket.new
+    @uds_socket = Socket.new(Socket::AF_UNIX, Socket::SOCK_DGRAM)
+    @threads = []
     @metrics = []
-
-    @socket.bind(@host, @port)
   end
 
   def start
-    @thread = Thread.new { loop { receive } }
-    @thread.abort_on_exception = true
+    @udp_socket.bind(@host, @port)
+    @uds_socket.bind(Addrinfo.unix(@socket_path))
+
+    @threads << Thread.new { loop { receive_from_udp_socket } }
+    @threads << Thread.new { loop { receive_from_uds_socket } }
+    @threads.each { |th| th.abort_on_exception = true }
   end
 
   def stop
-    @thread.kill
+    @threads.each(&:kill)
+    @udp_socket.close
+    @uds_socket.close
+    @threads = []
   end
 
   def wait_for_metrics(count: 1)
@@ -34,9 +46,17 @@ def wait_for_metrics(count: 1)
 
   private
 
-  def receive
-    data, sender = @socket.recvfrom(512)
+  def receive_from_udp_socket
+    data, _ = @udp_socket.recvfrom(512)
+    add_metrics(data)
+  end
+
+  def receive_from_uds_socket
+    data, _ = @uds_socket.recvfrom(512)
+    add_metrics(data)
+  end
 
+  def add_metrics(data)
     data.split("\n").each do |message|
       metric = message.split(":").first
       @metrics << metric if metric

spec/functional/datadog_spec.rb

@@ -5,12 +5,31 @@
 require "fake_datadog_agent"
 
 describe "Reporting metrics to Datadog", functional: true do
-  example "reporting connection metrics" do
-    agent = FakeDatadogAgent.new
+  let(:agent) { FakeDatadogAgent.new }
 
+  before do
+    agent.start
+  end
+
+  after do
+    agent.stop
+  end
+
+  example "reporting connection metrics using UDP socket" do
     Kafka::Datadog.port = agent.port
 
-    agent.start
+    kafka.topics
+
+    agent.wait_for_metrics(count: 4)
+
+    expect(agent.metrics).to include("ruby_kafka.api.calls")
+    expect(agent.metrics).to include("ruby_kafka.api.latency")
+    expect(agent.metrics).to include("ruby_kafka.api.request_size")
+    expect(agent.metrics).to include("ruby_kafka.api.response_size")
+  end
+
+  example "reporting connection metrics using Unix domain socket" do
+    Kafka::Datadog.socket_path = agent.socket_path
 
     kafka.topics