Add mysql service connectivity check

lib/nerve/service_watcher.rb

@@ -1,6 +1,7 @@
 require 'nerve/service_watcher/tcp'
 require 'nerve/service_watcher/http'
 require 'nerve/service_watcher/rabbitmq'
+require 'nerve/service_watcher/mysql'
 
 module Nerve
   class ServiceWatcher

lib/nerve/service_watcher/mysql.rb

@@ -0,0 +1,40 @@
+require 'nerve/service_watcher/base'
+
+module Nerve
+  module ServiceCheck
+    class MysqlServiceCheck < BaseServiceCheck
+      require 'mysql2'
+
+      def initialize(opts={})
+        super
+
+        raise ArgumentError, "missing required argument 'user' in mysql check" unless opts['user']
+
+        @user = opts['user']
+        @pass = opts['password'] || ''
+        @host = opts['host'] || '127.0.0.1'
+        @port = opts['port'] || '3306'
+      end
+
+      def check
+        # the idea of health check is similar to haproxy option mysql-check
+        log.debug "nerve: running mysql health check #{@name}"
+
+        begin
+          log.debug "nerve: mysql connect #{@host}:#{@port} as #{@user}"
+          conn = Mysql2::Client.new(:host => @host, :username => @user, :password => @pass, :port => @port)
+        rescue Mysql2::Error => e
+          log.debug "nerve: mysql check error #{e.errno}: #{e.error}"
+          return false
+        ensure
+          conn.close if conn
+        end
+
+        return true
+      end
+    end
+
+    CHECKS ||= {}
+    CHECKS['mysql'] = MysqlServiceCheck
+  end
+end

nerve.gemspec

@@ -25,6 +25,7 @@ Gem::Specification.new do |gem|
   gem.add_runtime_dependency "zk", "~> 1.9.2"
   gem.add_runtime_dependency "bunny", "= 1.1.0"
   gem.add_runtime_dependency "etcd", "~> 0.2.3"
+  gem.add_runtime_dependency "mysql2", "~> 0.4.2"
 
   gem.add_development_dependency "rake"
   gem.add_development_dependency "rspec", "~> 3.1.0"