refactor(scheduler): 优化调度器优雅停机机制

- 添加优雅停机等待时间常量配置
- 调度线程增加优雅停机等待逻辑
- 修正日志记录器声明为final
- 更新文档中的TODO状态为ING状态

doc/XXL-JOB官方文档.md

@@ -2748,8 +2748,10 @@ public void execute() {
 - 2、【优化】调度线程事务提交逻辑调整，避免边界条件下线程异常退出，增强健壮性；
 - 3、【优化】调度日志列表排序逻辑优化，提升易读性；
 - 4、【优化】表格交互优化：优化分页显示配置；禁用分页循环；多选行操作优化/默认单选；
-- 5、【TODO】任务调度触发后分批批量更新，提升调度性能；
-- 6、【TODO】优雅停机：服务端停机，检测时间轮非空sleep 5s；客户端停机，检测任务运行中，server停止后sleep5s；
+- 5、【ING】优雅停机：服务端停机，检测时间轮非空sleep 5s；
+  - 客户端停机，检测任务运行中，server停止后sleep5s；
+- 6、【TODO】任务调度触发后分批批量更新，提升调度性能；
+
 
 
 ### TODO LIST

xxl-job-admin/src/main/java/com/xxl/job/admin/scheduler/thread/JobScheduleHelper.java

@@ -24,7 +24,14 @@ public class JobScheduleHelper {
     private static final Logger logger = LoggerFactory.getLogger(JobScheduleHelper.class);
 
 
-    public static final long PRE_READ_MS = 5000;    // pre read
+    /**
+     * pre-read time for scheduler, increase efficiency
+     */
+    public static final long PRE_READ_MS = 5000;
+    /*
+    * elegant shutdown wait seconds
+     */
+    private static final long ELEGANT_SHUTDOWN_WAITING_SECONDS = 10;
 
     private Thread scheduleThread;
     private Thread ringThread;
@@ -316,7 +323,7 @@ public class JobScheduleHelper {
             }
         }
 
-        // if has ring data
+        // if has ring data, wait for elegent shutdown
         boolean hasRingData = false;
         if (MapTool.isNotEmpty(ringData)) {
             for (int second : ringData.keySet()) {
@@ -329,7 +336,7 @@ public class JobScheduleHelper {
         }
         if (hasRingData) {
             try {
-                TimeUnit.SECONDS.sleep(8);
+                TimeUnit.SECONDS.sleep(ELEGANT_SHUTDOWN_WAITING_SECONDS);
             } catch (Throwable e) {
                 logger.error(e.getMessage(), e);
             }

xxl-job-admin/src/main/java/com/xxl/job/admin/scheduler/thread/JobTriggerPoolHelper.java

@@ -14,7 +14,7 @@ import java.util.concurrent.atomic.AtomicInteger;
  * @author xuxueli 2018-07-03 21:08:07
  */
 public class JobTriggerPoolHelper {
-    private static Logger logger = LoggerFactory.getLogger(JobTriggerPoolHelper.class);
+    private static final Logger logger = LoggerFactory.getLogger(JobTriggerPoolHelper.class);
 
 
     // ---------------------- trigger pool ----------------------