mysql adapter

Gemfile.lock

@@ -45,6 +45,7 @@ GEM
       ffi (~> 1.0)
     msgpack (1.7.2)
     multipart-post (2.3.0)
+    mysql2 (0.5.5)
     rack (3.0.8)
     rack-test (2.1.0)
       rack (>= 1.3)
@@ -79,6 +80,7 @@ DEPENDENCIES
   dogstatsd-ruby (<= 4.8.3)
   faraday (~> 1)
   faraday-rack
+  mysql2 (>= 0.5)
   network_resiliency!
   rack
   rack-test

lib/network_resiliency.rb

@@ -5,6 +5,7 @@ module Adapter
     autoload :HTTP, "network_resiliency/adapter/http"
     autoload :Faraday, "network_resiliency/adapter/faraday"
     autoload :Redis, "network_resiliency/adapter/redis"
+    autoload :Mysql, "network_resiliency/adapter/mysql"
   end
 
   extend self
@@ -22,6 +23,8 @@ def patch(*adapters)
         Adapter::HTTP.patch
       when :redis
         Adapter::Redis.patch
+      when :mysql
+        Adapter::Mysql.patch
       else
         raise NotImplementedError
       end

lib/network_resiliency/adapter/mysql.rb

@@ -0,0 +1,52 @@
+gem "mysql2", ">= 0.5"
+require "mysql2"
+
+module NetworkResiliency
+  module Adapter
+    module Mysql
+      extend self
+
+      def patch
+        return if patched?
+
+        Mysql2::Client.prepend(Instrumentation)
+      end
+
+      def patched?
+        Mysql2::Client.ancestors.include?(Instrumentation)
+      end
+
+      module Instrumentation
+        def connect(_, _, host, *args)
+          # timeout = query_options[:connect_timeout]
+
+          return super unless NetworkResiliency.enabled?(:mysql)
+
+          begin
+            ts = -NetworkResiliency.timestamp
+
+            super
+          rescue Mysql2::Error::TimeoutError => e
+            # capture error
+            raise
+          ensure
+            ts += NetworkResiliency.timestamp
+
+            NetworkResiliency.record(
+              adapter: "mysql",
+              action: "connect",
+              destination: host,
+              error: e&.class,
+              duration: ts,
+            )
+          end
+        end
+
+        # def query(sql, options = {})
+        #   puts "query"
+        #   super
+        # end
+      end
+    end
+  end
+end

network_resiliency.gemspec

@@ -18,6 +18,7 @@ Gem::Specification.new do |s|
   s.add_development_dependency "dogstatsd-ruby", "<= 4.8.3"
   s.add_development_dependency "faraday", "~> 1"
   s.add_development_dependency "faraday-rack"
+  s.add_development_dependency "mysql2", ">= 0.5"
   s.add_development_dependency "rack"
   s.add_development_dependency "rack-test"
   s.add_development_dependency "redis", "~> 4"

spec/mysql_spec.rb

@@ -0,0 +1,74 @@
+describe NetworkResiliency::Adapter::Mysql, :mock_mysql do
+  before do
+    stub_const("Mysql2::Client", klass_mock)
+  end
+
+  let(:klass_mock) { Class.new(Mysql2::Client) }
+
+  describe ".patch" do
+    subject do
+      described_class.patched?
+    end
+
+    it { is_expected.to be false }
+
+    context "when patched" do
+      before do
+        allow(klass_mock).to receive(:prepend).and_call_original
+        described_class.patch
+      end
+
+      it { is_expected.to be true }
+
+      it "will only patch once" do
+        expect(klass_mock).to have_received(:prepend).once
+
+        described_class.patch
+
+        expect(klass_mock).to have_received(:prepend).once
+      end
+    end
+  end
+
+  describe ".connect" do
+    subject do
+      mysql rescue Mysql2::Error::ConnectionError
+
+      NetworkResiliency.statsd
+    end
+
+    let(:host) { "my.fav.sql.com" }
+    let(:mysql) { Mysql2::Client.new(host: host, socket: mock_mysql) }
+    # let(:select) { mysql.query("SELECT 1").first.first.last }
+
+    before do
+      described_class.patch
+    end
+
+    it "can not connect to a mysql server" do
+      expect { mysql }.to raise_error(Mysql2::Error::ConnectionError)
+    end
+
+    it "logs connection" do
+      is_expected.to have_received(:distribution).with(
+        /connect/,
+        Numeric,
+        anything,
+      )
+    end
+
+    it "logs duration" do
+      is_expected.to have_received(:distribution) do |_, duration, _|
+        expect(duration).to be > 0
+      end
+    end
+
+    it "tags the destination host" do
+      is_expected.to have_received(:distribution).with(
+        String,
+        Numeric,
+        tags: include(destination: host),
+      )
+    end
+  end
+end

spec/support/mock_mysql.rb

@@ -0,0 +1,41 @@
+require "mysql2"
+require "socket"
+
+module Helpers
+  module MockMysql
+    SOCKET_PATH = "/tmp/mock_mysql.sock"
+
+    def mock_mysql
+      # raise Mysql2::Error::TimeoutError.new("fake timeout", nil, error_number = 1205)
+
+      File.delete(SOCKET_PATH) if File.exists?(SOCKET_PATH)
+
+      server = UNIXServer.new(SOCKET_PATH)
+
+      Thread.new do
+        socket, _ = server.accept
+
+        # line = socket.recv(1024)
+        # line = socket.gets.chomp
+        # puts "mysql server: #{line}"
+
+        # server_socket.write("#{resp}")
+        # server_socket.write("\r\n") unless resp.end_with?("\r\n")
+      ensure
+        socket&.close
+      end
+
+      SOCKET_PATH
+    end
+  end
+end
+
+
+RSpec.configure do |config|
+  config.include Helpers::MockMysql, :mock_mysql
+
+  config.after(mock_mysql: true) do
+    # clean up socket file
+    File.delete(Helpers::MockMysql::SOCKET_PATH) if File.exists?(Helpers::MockMysql::SOCKET_PATH)
+  end
+end