记一次ThreadPoolTaskExecutor的坑

起因：

开发环境一切正常
部署到UAT环境后，项目中使用@Async修饰的方法没有执行。

临时解决方法：

先去掉该注解改成同步执行。

问题排查过程：

1.创建一个测试controller，用于观察线程池情况

package org.example.controller;import com.alibaba.fastjson.JSON;
import com.alibaba.fastjson.JSONObject;
import org.example.service.MyTestService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.ApplicationContext;
import org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;import java.util.Map;@RequestMapping(value = "/test")
@RestController
public class MyTestController {@Autowiredprivate ApplicationContext applicationContext;@Autowiredprivate MyTestService myTestService;@GetMapping({"/threadPools"})public JSONObject threadPools(){Map<String, ThreadPoolTaskExecutor> threadMap = applicationContext.getBeansOfType(ThreadPoolTaskExecutor.class);String json = JSON.toJSONString(threadMap);JSONObject jsonObject = JSON.parseObject(json);return jsonObject;}@GetMapping(value = "/test1")public String test1(){myTestService.test1();return "ok";}}

package org.example.service;import lombok.extern.slf4j.Slf4j;
import org.springframework.scheduling.annotation.Async;
import org.springframework.stereotype.Service;@Slf4j
@Service
public class MyTestService {@Async//("taskExecutor")public void test1(){log.info("test1");}}

浏览器方法该接口：http://localhost:8080/test/threadPools

{"taskExecutor": {"activeCount": 3,"threadNamePrefix": "taskExecutor-","poolSize": 3,"threadPoolExecutor": {"activeCount": 3,"threadFactory": {"$ref": "$.taskExecutor"},"largestPoolSize": 3,"poolSize": 3,"taskCount": 3,"rejectedExecutionHandler": {},"corePoolSize": 3,"completedTaskCount": 0,"terminating": false,"maximumPoolSize": 5,"queue": [],"shutdown": false,"terminated": false},"corePoolSize": 3,"threadPriority": 5,"maxPoolSize": 5,"keepAliveSeconds": 60,"daemon": false}
}

再调用test1接口把普通任务提交到该线程池：http://localhost:8080/test/test1
再观察线程池情况：

{"taskExecutor": {"activeCount": 3,"threadNamePrefix": "taskExecutor-","poolSize": 3,"threadPoolExecutor": {"activeCount": 3,"threadFactory": {"$ref": "$.taskExecutor"},"largestPoolSize": 3,"poolSize": 3,"taskCount": 5,"rejectedExecutionHandler": {},"corePoolSize": 3,"completedTaskCount": 0,"terminating": false,"maximumPoolSize": 5,"queue": [{"cancelled": false,"done": false},{"cancelled": false,"done": false}],"shutdown": false,"terminated": false},"corePoolSize": 3,"threadPriority": 5,"maxPoolSize": 5,"keepAliveSeconds": 60,"daemon": false}
}

发现等待队列queue节点多了几个，且activeCount一直保持3，而corePoolSize刚好也是3。
此时有理由怀疑，有3个任务没有结束，导致新的任务只能放在等待队列，因此没有执行新任务。

通过本地debug发现，系统启动后，公司的框架代码会往默认线程池里提交3个任务，而这3个任务都是while(true)循环。

package org.example.event;import lombok.Getter;
import lombok.Setter;
import lombok.ToString;
import org.springframework.context.ApplicationEvent;
@Getter
@Setter
@ToString
public class MyEvent  extends ApplicationEvent {public MyEvent(Object source) {super(source);}
}

package org.example.init;import org.example.event.MyEvent;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.ApplicationContext;
import org.springframework.stereotype.Component;import javax.annotation.PostConstruct;@Component
public class Initor {@Autowiredprivate ApplicationContext applicationContext;@PostConstructprivate void init(){applicationContext.publishEvent(new MyEvent("这是自定义事件1"));applicationContext.publishEvent(new MyEvent("这是自定义事件2"));applicationContext.publishEvent(new MyEvent("这是自定义事件3"));}
}

package org.example.listener;import lombok.extern.slf4j.Slf4j;
import org.example.event.MyEvent;
import org.springframework.context.ApplicationListener;
import org.springframework.scheduling.annotation.Async;
import org.springframework.stereotype.Service;@Slf4j
@Service
public class MyListener implements ApplicationListener<MyEvent>{@Async//("taskExecutor")@Overridepublic void onApplicationEvent(MyEvent myEvent) {log.info("myEvent:{}",myEvent);log.info("开始死循环");//3个死循环进入默认线程池，而默认线程池核心线程数是3，后续加入的任务都只能放在等待队列，永远没机会执行。while (true){try {Thread.sleep(10000);log.info("myEvent");} catch (InterruptedException e) {throw new RuntimeException(e);}}}
}

通过该线程池名称，搜索到该线程池的配置类：

package org.example.config;import lombok.extern.slf4j.Slf4j;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor;import java.util.concurrent.Executor;
import java.util.concurrent.ThreadPoolExecutor;@Slf4j
@Configuration
public class ThreadPoolConfig {@Bean//("taskExecutor")public Executor taskExecutor() {ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();//核心线程数executor.setCorePoolSize(3);
//        executor.setCorePoolSize(Runtime.getRuntime().availableProcessors());//最大线程数executor.setMaxPoolSize(5);//队列容量executor.setQueueCapacity(1000);//线程活跃时间（秒）executor.setKeepAliveSeconds(60);//默认线程名称executor.setThreadNamePrefix("taskExecutor-");//拒绝策略executor.setRejectedExecutionHandler(new ThreadPoolExecutor.CallerRunsPolicy());//等待所有任务结束后再关闭线程池executor.setWaitForTasksToCompleteOnShutdown(true);
//        executor.initialize();不需要这句代码，因为ThreadPoolTaskExecutor实现了InitializingBean接口，其afterPropertiesSet方法会调用initialize()。return executor;}}

设置线程池的核心线程数使用了系统核心数，在UAT环境刚好是3，而其他环境大于3，这就是到了UAT环境突然有问题的原因了。

通过深入debug，发现spring获取默认线程池，是通过beanName为“taskExecutor”来查找的，而上面自定义线程池， @Bean注解没有指定名称，则取方法名“taskExecutor”，而该名称，碰巧是spring默认线程池的名称，导致该自定义线程池覆盖了spring的默认线程池，从而使用@Async（没有指定名称）都用的该线程池。