Fix scheduled task instance mode execution and queue management

[Copilot]

Scheduled tasks in multi-instance mode stopped executing after the queue filled up (5 tasks). Single-instance mode failed to kill old tasks before starting new ones due to missing status tracking.

Root Causes

Multi-instance mode: Fixed queue limit of 5 caused task rejection when long-running tasks accumulated (e.g., 500s tasks scheduled every minute)

Single-instance mode:

• Status never updated to running, preventing detection of active tasks
• Default behavior treated null/undefined as multi-instance instead of single-instance

Changes

back/shared/runCron.ts

• Add status updates: running on spawn, idle on exit (with error handling)
• Fix default: allow_multiple_instances !== 1 treats null/undefined as single-instance
• Enable proper task killing in single-instance mode via status tracking

back/shared/pLimit.ts

• Query allow_multiple_instances per task to determine queue limits
• Single-instance: limit 2 (allows queuing new task while killing old)
• Multi-instance: limit 10 (increased from 5)
• Import CrontabModel at module level to avoid repeated dynamic imports

// Before: null/undefined incorrectly allowed multiple instances
const allowSingleInstances = existingCron?.allow_multiple_instances === 0;

// After: null/undefined defaults to single-instance mode
const isSingleInstanceMode = existingCron?.allow_multiple_instances !== 1;

Original prompt

---

This section details on the original issue you should resolve

<issue_title>定时任务-单/多实例模式未触发</issue_title>
<issue_description>### Qinglong version

2.20.1

Steps to reproduce

作者你好，我在使用的时候发现了bug，根据实例模式介绍，单实例模式启动新任务会停止旧任务；多实例模式则会同时运行

我写了以下代码：
`
import random
import time
from datetime import datetime

now = datetime.now()

name=(random.randint(1, 100)) # 生成1-100的随机整数

print(str(now)+'1开始运行:'+str(name))

time.sleep(500)

print(str(now)+'3运行结束:'+str(name))
`

定时规则：*/1 * * * *
实例模式:多实例

通过观察日志：

开始执行... 2025-12-30 17:23:01

2025-12-30 17:23:01.4253411开始运行:8
2025-12-30 17:23:01.4253413运行结束:8

执行结束... 2025-12-30 17:31:21 耗时 500 秒　　

---

开始执行... 2025-12-30 17:27:01

2025-12-30 17:27:01.3780611开始运行:40
2025-12-30 17:27:01.3780613运行结束:40

执行结束... 2025-12-30 17:35:21 耗时 500 秒　　　　　

　　　

预期是：

每分钟执行一次，在多实例的模式下，应该会每分钟都有日志产生，都开始运行，然后每个任务独立完成，之前设置的time.sleep(80)前几分钟正常到后面日志只有 17:58、17:59、18:01中间的18:00没有记录 为了更好的观察 我改成了500s 于是这个差距拉开得更加明显，后续由于内存不够吧报错了，然后有按每分钟一次运行

日志我打包好了：https://wwbwu.lanzoue.com/iJoDN3eujoxe

单实例模式我也测试过 到点后程序运行但是不会停止上次的任务
　　　

What is expected?

1

What is actually happening?

1

System Info

Any additional comments?

</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes 定时任务-单/多实例模式未触发 #2892

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Project	Deployment	Review	Updated (UTC)
qinglong	Ready	Preview, Comment	Dec 30, 2025 4:46pm
qinglong-back	Ready	Preview, Comment	Dec 30, 2025 4:46pm