How to Re‑trigger a Stalled Spring Scheduled Task with Arthas

Background

Recently an intern was asked to replace a shell script that checks connectivity to a target website with Java code.

<ol>
<li><code>#!/bin/bash</code></li>
<li><code>URL="https://www.baidu"</code></li>
<li><code>HTTP_CODE=`curl -o /dev/null -s -w "%{http_code}" "${URL}"`</code></li>
<li><code>#echo $HTTP_CODE</code></li>
<li><code>if [ $HTTP_CODE != '200' ]; then</code></li>
<li><code>curl 'https://oapi.dingtalk.com/robot/send?access_token=xx' \</code></li>
<li><code>-H 'Content-Type: application/json' \</code></li>
<li><code>-d '{"msgtype": "text",</code></li>
<li><code>        "text": {</code></li>
<li><code>             "content": "百度平台状态不正常，请注意！"</code></li>
<li><code>        },</code></li>
<li><code>        "isAtAll": true</code></li>
<li><code>      }'</code></li>
<li><code>fi</code></li>
</ol>

Implementation

Using Spring Task

<ol>
<li><code>@Scheduled(cron = "0 0 0/1 * * ? ")</code></li>
<li><code>public void startSchedule(){</code></li>
<li><code>    log.info("开始执行定时任务 ，检测百度网站连通性");</code></li>
<li><code>    try{</code></li>
<li><code>        HttpResponse response = HttpRequest.get("").execute();</code></li>
<li><code>        if(HttpStatus.HTTP_OK != response.getStatus()){
            this.send2DingTalk(response.getStatus());
        }</code></li>
<li><code>        log.info("请求百度成功，返回报文:{}", response.body());</code></li>
<li><code>    }catch(HttpException e){</code></li>
<li><code>        log.error("请求异常百度:{}", e);
        this.send2DingTalk(e.getMessage());
    }</code></li>
<li><code>    log.info("执行检测百度网站连通任务完毕");</code></li>
<li><code>}</code></li>
</ol>

Problem Description

The task runs hourly on a server, but the Java code never sends the DingTalk notification; logs show only the start message.

Logs show the start message but no end message, suggesting the task is stuck.

Need a way to trigger the failure path quickly for debugging.

Spring Task has no UI or API to invoke manually.

Reproducing the Issue with Arthas

Obtain the Spring ApplicationContext and invoke the startSchedule method directly.

Identify the Monitoring Point

Spring MVC requests go through RequestMappingHandlerAdapter and its invokeHandlerMethod.

The class contains getApplicationContext() to retrieve the context.

@Nullable
public final ApplicationContext getApplicationContext() throws IllegalStateException{
    if(this.applicationContext == null && this.isContextRequired()){
        throw new IllegalStateException("ApplicationObjectSupport instance ["+this+"] does not run in an ApplicationContext");
    }else{
        return this.applicationContext;
    }
}

Execute any request to capture the target RequestMappingHandlerAdapter and then call getApplicationContext().

Arthas tt Command to Get ApplicationContext

Run

tt -t org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter invokeHandlerMethod

to trace the method.

After a normal web request, the trace captures the target bean.

Then execute an OGNL expression to invoke the scheduled bean:

tt -i 1000 -w 'target.getApplicationContext().getBean("baiduSchedule").startSchedule()'

The task is re‑triggered.

Root cause: the Hutool HTTP utility used in the script lacked a timeout, causing an indefinite wait and preventing the catch block from executing.

Summary

Do not run such operations in production; the article only provides a proof‑of‑concept.

The core technique is using Arthas to fetch the Spring ApplicationContext and invoke a bean method.

Arthas is an open‑source Java diagnostic tool from Alibaba, widely used by developers.

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