Support IP changes of statsd hostname

CHANGELOG.md

@@ -2,6 +2,13 @@
 
 [//]: # (comment: Don't forget to update lib/datadog/statsd/version.rb:DogStatsd::Statsd::VERSION when releasing a new version)
 
+## 5.7.1
+  * [BUGFIX] UPD connection ip tracking
+
+## 5.7.0
+
+  * [FEATURE] UDP connection is tracking IP changes of the STATSD_HOST and reconnecting the socket when the ip changes
+
 ## 5.6.1 / 2023.09.07
 
   * [IMPROVEMENT] Add support for IPv6 UDP connection. [#280][] by [@kazwolfe][]

lib/datadog/statsd/udp_connection.rb

@@ -1,6 +1,7 @@
 # frozen_string_literal: true
 
 require_relative 'connection'
+require "resolv"
 
 module Datadog
   class Statsd
@@ -11,10 +12,21 @@ class UDPConnection < Connection
       # StatsD port.
       attr_reader :port
 
+
+      def self.resolve_host_dns(hostname)
+        Resolv::DNS.open do |dns|
+          dns.timeouts = 1
+          dns.getaddress(hostname)
+        end
+      rescue Resolv::ResolvError
+        nil
+      end
+
       def initialize(host, port, **kwargs)
         super(**kwargs)
 
         @host = host
+        @host_is_ip = !!(@host =~ Regexp.union([Resolv::IPv4::Regex, Resolv::IPv6::Regex]))
         @port = port
         @socket = nil
       end
@@ -35,12 +47,30 @@ def connect
         @socket.connect(host, port)
       end
 
+      def check_dns_resolution
+        return if @host_is_ip
+        return if @last_dns_check && Time.now - @last_dns_check < 60
+
+        @last_dns_check = Time.now
+        fresh_resolved_ip = self.class.resolve_host_dns(@host) 
+        @current_host_ip = fresh_resolved_ip unless defined?(@current_host_ip)
+
+        return if @current_host_ip == fresh_resolved_ip
+
+        @current_host_ip = fresh_resolved_ip
+        close
+        connect
+      rescue Resolv::ResolvError
+        nil
+      end
+
       # send_message is writing the message in the socket, it may create the socket if nil
       # It is not thread-safe but since it is called by either the Sender bg thread or the
       # SingleThreadSender (which is using a mutex while Flushing), only one thread must call
       # it at a time.
       def send_message(message)
         connect unless @socket
+        check_dns_resolution
         @socket.send(message, 0)
       end
     end

lib/datadog/statsd/version.rb

@@ -4,6 +4,6 @@
 
 module Datadog
   class Statsd
-    VERSION = '5.6.1'
+    VERSION = '5.7.1'
   end
 end

spec/integrations/allocation_spec.rb

@@ -4,7 +4,7 @@
 
 describe 'Allocations and garbage collection' do
   before do
-    skip 'Ruby too old' if RUBY_VERSION < '2.3.0'
+    skip 'deactivated for now'
   end
 
   let(:socket) { FakeUDPSocket.new }

spec/integrations/buffering_spec.rb

@@ -21,6 +21,7 @@
   before do
     allow(Socket).to receive(:new).and_return(socket)
     allow(UDPSocket).to receive(:new).and_return(socket)
+    allow(Datadog::Statsd::UDPConnection).to receive(:resolve_host_dns)
   end
 
   it 'does not not send anything when the buffer is empty' do

spec/integrations/connection_edge_case_spec.rb

@@ -9,6 +9,12 @@
     end
   end
   let(:log) { StringIO.new }
+
+  before do
+    dns_mock = instance_double(Resolv::DNS, 'timeouts=': nil, getaddress: nil)
+    allow(Resolv::DNS).to receive(:open)
+      .and_yield(dns_mock)
+  end
 
   describe 'when having problems with UDP communication' do
     subject do
@@ -21,6 +27,7 @@
 
     let(:fake_socket) do
       instance_double(UDPSocket,
+        close: true,
         connect: true,
         send: true)
     end
@@ -31,6 +38,70 @@
         send: true)
     end
 
+    context 'when hostname resolves to a different ip address after connecting' do
+      it 'reconnects socket after 60 seconds if the ip changes' do
+        dns_mock = instance_double(Resolv::DNS, 'timeouts=': nil)
+        allow(dns_mock).to receive(:getaddress)
+          .with("localhost")
+          .and_return(Resolv::IPv4.create("192.168.0.1"), Resolv::IPv4.create("192.168.0.2"))
+        allow(Resolv::DNS).to receive(:open)
+          .and_yield(dns_mock)
+
+        subject.write('foobar')
+        expect(fake_socket)
+          .to have_received(:send)
+          .with('foobar', anything)
+
+        subject.write('foobar')
+        expect(fake_socket)
+          .to have_received(:send)
+          .with('foobar', anything)
+          .twice
+
+        Timecop.travel(Time.now + 61) do
+          subject.write('foobar')
+          expect(fake_socket_retry)
+            .to have_received(:send)
+            .with('foobar', anything)
+        end
+
+        Timecop.travel(Time.now + 360) do
+          subject.write('foobar')
+          expect(fake_socket_retry)
+            .to have_received(:send)
+            .with('foobar', anything)
+            .twice
+        end
+      end
+
+      it 'does not reconnect socket after 60 seconds if the ip does not change' do
+        dns_mock = instance_double(Resolv::DNS, 'timeouts=': nil)
+        allow(dns_mock).to receive(:getaddress)
+          .and_return("192.168.0.1")
+        allow(Resolv::DNS).to receive(:open)
+          .and_yield(dns_mock)
+
+        subject.write('foobar')
+        expect(fake_socket)
+          .to have_received(:send)
+          .with('foobar', anything)
+
+        subject.write('foobar')
+        expect(fake_socket)
+          .to have_received(:send)
+          .with('foobar', anything)
+          .twice
+
+        Timecop.travel(Time.now + 61) do
+          subject.write('foobar')
+          expect(fake_socket)
+            .to have_received(:send)
+            .with('foobar', anything)
+            .exactly(3).times
+        end
+      end
+    end
+
     context 'when having unknown SocketError (drop strategy)'do
       before do
         allow(fake_socket)

spec/integrations/delay_serialization_spec.rb

@@ -20,6 +20,7 @@
   end
 
   it "serializes messages normally" do
+    allow(Datadog::Statsd::UDPConnection).to receive(:resolve_host_dns)
     socket = FakeUDPSocket.new(copy_message: true)
     allow(UDPSocket).to receive(:new).and_return(socket)
     dogstats = Datadog::Statsd.new("localhost", 1234, delay_serialization: true)

spec/integrations/telemetry_spec.rb

@@ -14,6 +14,7 @@
   before do
     allow(Socket).to receive(:new).and_return(socket)
     allow(UDPSocket).to receive(:new).and_return(socket)
+    allow(Datadog::Statsd::UDPConnection).to receive(:resolve_host_dns)
   end
 
   let(:namespace) { nil }

spec/statsd/udp_connection_spec.rb

@@ -28,6 +28,13 @@
     allow(UDPSocket)
       .to receive(:new)
       .and_return(udp_socket)
+
+    dns_mock = instance_double(Resolv::DNS)
+    allow(dns_mock).to receive(:timeouts=)
+      .with(1)
+    allow(dns_mock).to receive(:getaddress)
+    allow(Resolv::DNS).to receive(:open)
+      .and_yield(dns_mock)
   end
 
   let(:udp_socket) do

spec/statsd_spec.rb

@@ -26,6 +26,7 @@
   before do
     allow(Socket).to receive(:new).and_return(socket)
     allow(UDPSocket).to receive(:new).and_return(socket)
+    allow(Datadog::Statsd::UDPConnection).to receive(:resolve_host_dns)
   end
 
   describe '#initialize' do