注册监控线程优化，降低死锁几率；

doc/XXL-JOB官方文档.md

 - 7、[ING]cron在线生成工具；
 - 8、[ING]任务、执行器数据全量本地缓存；新增消息表广播通知；
 - 9、[ING]任务触发组件优化，常规1s预加载一次，轮空时主动休眠4s；
+- 10、注册监控线程优化，降低死锁几率；
 
 
 ### TODO LIST

doc/db/tables_xxl_job.sql

   `registry_value` varchar(255) NOT NULL,
   `update_time` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP,
   PRIMARY KEY (`id`),
-  KEY `i_g_k_v` (`registry_group`,`registry_key`,`registry_value`),
-  KEY `i_u` (`update_time`)
+  KEY `i_g_k_v` (`registry_group`,`registry_key`,`registry_value`)
 ) ENGINE=InnoDB DEFAULT CHARSET=utf8;
 
 CREATE TABLE `xxl_job_group` (

xxl-job-admin/src/main/java/com/xxl/job/admin/core/thread/JobRegistryMonitorHelper.java

 						if (groupList!=null && !groupList.isEmpty()) {
 
 							// remove dead address (admin/executor)
-							XxlJobAdminConfig.getAdminConfig().getXxlJobRegistryDao().removeDead(RegistryConfig.DEAD_TIMEOUT);
+							List<Integer> ids = XxlJobAdminConfig.getAdminConfig().getXxlJobRegistryDao().findDead(RegistryConfig.DEAD_TIMEOUT);
+							if (ids!=null && ids.size()>0) {
+								XxlJobAdminConfig.getAdminConfig().getXxlJobRegistryDao().removeDead(ids);
+							}
 
 							// fresh online address (admin/executor)
 							HashMap<String, List<String>> appAddressMap = new HashMap<String, List<String>>();

xxl-job-admin/src/main/java/com/xxl/job/admin/dao/XxlJobRegistryDao.java

 @Mapper
 public interface XxlJobRegistryDao {
 
-    public int removeDead(@Param("timeout") int timeout);
+    public List<Integer> findDead(@Param("timeout") int timeout);
+
+    public int removeDead(@Param("ids") List<Integer> ids);
 
     public List<XxlJobRegistry> findAll(@Param("timeout") int timeout);
 

xxl-job-admin/src/main/resources/mybatis-mapper/XxlJobRegistryMapper.xml

 		t.registry_value,
 		t.update_time
 	</sql>
+
+	<select id="findDead" parameterType="java.lang.Integer" resultType="java.lang.Integer" >
+		SELECT t.id
+		FROM xxl_job_registry AS t
+		WHERE t.update_time <![CDATA[ < ]]> DATE_ADD(NOW(),INTERVAL -#{timeout} SECOND)
+	</select>
 	
 	<delete id="removeDead" parameterType="java.lang.Integer" >
 		DELETE FROM xxl_job_registry
-		WHERE update_time <![CDATA[ < ]]> DATE_ADD(NOW(),INTERVAL -#{timeout} SECOND)
+		WHERE id in
+		<foreach collection="ids" item="item" open="(" close=")" separator="," >
+			#{item}
+		</foreach>
 	</delete>
 
 	<select id="findAll" parameterType="java.lang.Integer" resultMap="XxlJobRegistry">

xxl-job-admin/src/test/java/com/xxl/job/admin/dao/XxlJobRegistryDaoTest.java

 import org.springframework.test.context.junit4.SpringRunner;
 
 import javax.annotation.Resource;
+import java.util.Arrays;
 import java.util.List;
 
 @RunWith(SpringRunner.class)
 
         List<XxlJobRegistry> list = xxlJobRegistryDao.findAll(1);
 
-        int ret2 = xxlJobRegistryDao.removeDead(1);
+        int ret2 = xxlJobRegistryDao.removeDead(Arrays.asList(1));
     }
 
 }