任务失败告警邮件发送逻辑优化

doc/XXL-JOB官方文档.md

 - 14、新增Class的加载缓存，解决频繁加载Class会使jvm的方法区空间不足导致OOM的问题；
 - 15、调整首页报表默认区间为本周，避免日志量太大查询缓慢；
 - 16、LRU路由更新不及时问题修复；
-- 17、[迭代中]任务线程隔离：
+- 17、任务失败告警邮件发送逻辑优化；
+- 18、[迭代中]任务线程隔离：
     - 执行器测异步响应，不存在阻塞不需要隔离；
     - 调度中心共用单一调度线程池，可能导致调度阻塞需要线程隔离；调度线程池拆分为Fast/Slow两个，针对调度较慢的执行器地址请求，降级使用Slow线程池；考虑是否可以任务级隔离线程池；
 

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

 		// send monitor email
 		if (info!=null && info.getAlarmEmail()!=null && info.getAlarmEmail().trim().length()>0) {
 
+			// alarmContent
 			String alarmContent = "Alarm Job LogId=" + jobLog.getId();
 			if (jobLog.getTriggerCode() != ReturnT.SUCCESS_CODE) {
 				alarmContent += "<br>TriggerMsg=<br>" + jobLog.getTriggerMsg();
 				alarmContent += "<br>HandleCode=" + jobLog.getHandleMsg();
 			}
 
+			// email info
+			XxlJobGroup group = XxlJobAdminConfig.getAdminConfig().getXxlJobGroupDao().load(Integer.valueOf(info.getJobGroup()));
+			String personal = I18nUtil.getString("admin_name_full");
+			String title = I18nUtil.getString("jobconf_monitor");
+			String content = MessageFormat.format(mailBodyTemplate,
+					group!=null?group.getTitle():"null",
+					info.getId(),
+					info.getJobDesc(),
+					alarmContent);
+
 			Set<String> emailSet = new HashSet<String>(Arrays.asList(info.getAlarmEmail().split(",")));
 			for (String email: emailSet) {
-				XxlJobGroup group = XxlJobAdminConfig.getAdminConfig().getXxlJobGroupDao().load(Integer.valueOf(info.getJobGroup()));
-
-				String personal = I18nUtil.getString("admin_name_full");
-				String title = I18nUtil.getString("jobconf_monitor");
-				String content = MessageFormat.format(mailBodyTemplate,
-						group!=null?group.getTitle():"null",
-						info.getId(),
-						info.getJobDesc(),
-						alarmContent);
-
 
 				// make mail
 				try {

xxl-job-core/src/main/java/com/xxl/job/core/thread/ExecutorRegistryThread.java

 /**
  * Created by xuxueli on 17/3/2.
  */
-public class ExecutorRegistryThread extends Thread {
+public class ExecutorRegistryThread {
     private static Logger logger = LoggerFactory.getLogger(ExecutorRegistryThread.class);
 
     private static ExecutorRegistryThread instance = new ExecutorRegistryThread();

xxl-job-core/src/main/java/com/xxl/job/core/thread/JobLogFileCleanThread.java

  *
  * @author xuxueli 2017-12-29 16:23:43
  */
-public class JobLogFileCleanThread extends Thread {
+public class JobLogFileCleanThread {
     private static Logger logger = LoggerFactory.getLogger(JobLogFileCleanThread.class);
 
     private static JobLogFileCleanThread instance = new JobLogFileCleanThread();