[fix](Export) Fix the issue where the show export status stays stuck on EXPORTING. (#47974)

Problem Summary:

Each Export task will be deleted after execution in the finally block of
the TaskHandler#onTransientTaskHandle() method. Therefore, when removing
a task in the TransientTaskManager#cancelMemoryTask method, there should
be a check to see if the task exists. Otherwise, a null pointer
exception may occur, causing the Export Job status update to fail.

Author: BePPPower

fe/fe-core/src/main/java/org/apache/doris/load/ExportJob.java

@@ -713,7 +713,10 @@ private void cancelExportJobUnprotected(ExportFailMsg.CancelType type, String ms
         LOG.info("cancel export job {}", id);
     }
 
-    private void exportExportJob() {
+    private void exportExportJob() throws JobException {
+        if (getState() == ExportJobState.CANCELLED || getState() == ExportJobState.FINISHED) {
+            throw new JobException("export job has been {}, can not be update to `EXPORTING` state", getState());
+        }
         // The first exportTaskExecutor will set state to EXPORTING,
         // other exportTaskExecutors do not need to set up state.
         if (getState() == ExportJobState.EXPORTING) {

fe/fe-core/src/main/java/org/apache/doris/scheduler/disruptor/TaskHandler.java

@@ -23,7 +23,8 @@
 import org.apache.doris.scheduler.manager.TransientTaskManager;
 
 import com.lmax.disruptor.WorkHandler;
-import lombok.extern.log4j.Log4j2;
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
 
 /**
  * This class represents a work handler for processing event tasks consumed by a Disruptor.
@@ -32,9 +33,8 @@
  * If the event job execution fails, the work handler logs an error message and pauses the event job.
  * The work handler also handles system events by scheduling batch scheduler tasks.
  */
-@Log4j2
 public class TaskHandler implements WorkHandler<TaskEvent> {
-
+    private static final Logger LOG = LogManager.getLogger(TaskHandler.class);
 
     /**
      * Processes an event task by retrieving the associated event job and executing it if it is running.
@@ -50,7 +50,7 @@ public void onEvent(TaskEvent event) {
                 onTransientTaskHandle(event);
                 break;
             default:
-                log.warn("unknown task type: {}", event.getTaskType());
+                LOG.warn("unknown task type: {}", event.getTaskType());
                 break;
         }
     }
@@ -60,14 +60,14 @@ public void onTransientTaskHandle(TaskEvent taskEvent) {
         TransientTaskManager transientTaskManager = Env.getCurrentEnv().getTransientTaskManager();
         TransientTaskExecutor taskExecutor = transientTaskManager.getMemoryTaskExecutor(taskId);
         if (taskExecutor == null) {
-            log.info("Memory task executor is null, task id: {}", taskId);
+            LOG.info("Memory task executor is null, task id: {}", taskId);
             return;
         }
 
         try {
             taskExecutor.execute();
         } catch (JobException e) {
-            log.warn("Memory task execute failed, taskId: {}, msg : {}", taskId, e.getMessage());
+            LOG.warn("Memory task execute failed, taskId: {}, msg : {}", taskId, e.getMessage());
         } finally {
             transientTaskManager.removeMemoryTask(taskId);
         }

fe/fe-core/src/main/java/org/apache/doris/scheduler/manager/TransientTaskManager.java

@@ -63,10 +63,9 @@ public Long addMemoryTask(TransientTaskExecutor executor) throws JobException {
     }
 
     public void cancelMemoryTask(Long taskId) throws JobException {
-        try {
-            taskExecutorMap.get(taskId).cancel();
-        } finally {
-            removeMemoryTask(taskId);
+        TransientTaskExecutor transientTaskExecutor = taskExecutorMap.get(taskId);
+        if (transientTaskExecutor != null) {
+            transientTaskExecutor.cancel();
         }
     }