Fix scheduled task instance mode issues

- Fixed runCron to properly handle allow_multiple_instances setting
- Updated default behavior to single-instance mode for backward compatibility
- Added status updates (running/idle) to track task execution
- Fixed queue limit logic to respect instance mode settings
- For single-instance mode: allow up to 2 queued tasks to handle task killing
- For multi-instance mode: increased queue limit to 10 tasks

Co-authored-by: whyour <22700758+whyour@users.noreply.github.com>

back/shared/pLimit.ts

@@ -131,13 +131,39 @@ class TaskLimit {
     let runs = this.queuedCrons.get(cron.id);
     const result = runs?.length ? [...runs, fn] : [fn];
     const repeatTimes = this.repeatCronNotifyMap.get(cron.id) || 0;
-    if (result?.length > 5) {
+    
+    // Check instance mode from database to determine queue limit
+    let maxQueueSize = 10; // Default for multi-instance mode (increased from 5)
+    let isSingleInstanceMode = false;
+    try {
+      const { CrontabModel } = await import('../data/cron');
+      const cronRecord = await CrontabModel.findOne({
+        where: { id: Number(cron.id) },
+      });
+      
+      // Default to single instance mode (0) for backward compatibility
+      // allow_multiple_instances is 1 for multi-instance, 0 or null/undefined for single instance
+      isSingleInstanceMode = cronRecord?.allow_multiple_instances !== 1;
+      
+      if (isSingleInstanceMode) {
+        // For single instance mode, allow up to 2 queued tasks
+        // This allows the new task to be queued while the old one is being killed
+        maxQueueSize = 2;
+      }
+    } catch (error) {
+      Logger.error(
+        `[schedule][检查实例模式失败] 任务ID: ${cron.id}, 错误: ${error}`,
+      );
+    }
+    
+    if (result?.length > maxQueueSize) {
       if (repeatTimes < 3) {
         this.repeatCronNotifyMap.set(cron.id, repeatTimes + 1);
+        const modeStr = isSingleInstanceMode ? '单实例' : '多实例';
         this.client.systemNotify(
           {
             title: '任务重复运行',
-            content: `任务：${cron.name}，命令：${cron.command}，定时：${cron.schedule}，处于运行中的超过 5 个，请检查定时设置`,
+            content: `任务：${cron.name}（${modeStr}模式），命令：${cron.command}，定时：${cron.schedule}，处于运行中的超过 ${maxQueueSize} 个，请检查定时设置`,
           },
           (err, res) => {
             if (err) {

back/shared/runCron.ts

@@ -15,11 +15,12 @@ export function runCron(cmd: string, cron: ICron): Promise<number | void> {
         });
 
         // Default to single instance mode (0) for backward compatibility
-        const allowSingleInstances =
-          existingCron?.allow_multiple_instances === 0;
+        // allow_multiple_instances is 1 for multi-instance, 0 or null/undefined for single instance
+        const isSingleInstanceMode =
+          existingCron?.allow_multiple_instances !== 1;
 
         if (
-          allowSingleInstances &&
+          isSingleInstanceMode &&
           existingCron &&
           existingCron.pid &&
           (existingCron.status === CrontabStatus.running ||
@@ -49,6 +50,12 @@ export function runCron(cmd: string, cron: ICron): Promise<number | void> {
       );
       const cp = spawn(cmd, { shell: '/bin/bash' });
 
+      // Update status to running after spawning the process
+      await CrontabModel.update(
+        { status: CrontabStatus.running, pid: cp.pid },
+        { where: { id: Number(cron.id) } },
+      );
+
       cp.stderr.on('data', (data) => {
         Logger.info(
           '[schedule][执行任务失败] 命令: %s, 错误信息: %j',
@@ -66,6 +73,11 @@ export function runCron(cmd: string, cron: ICron): Promise<number | void> {
 
       cp.on('exit', async (code) => {
         taskLimit.removeQueuedCron(cron.id);
+        // Update status to idle after task completes
+        await CrontabModel.update(
+          { status: CrontabStatus.idle, pid: undefined },
+          { where: { id: Number(cron.id) } },
+        );
         Logger.info(
           '[schedule][执行任务结束] 参数: %s, 退出码: %j',
           JSON.stringify({