未设置超时时间导致线程池资源耗尽，排查过程

错误分析：

@Scheduled进行定时任务的时候，spring会创建一个线程，然后用这个线程来执行任务，如果这个任务阻塞了，那么这个任务就会停滞，出现不执行的情况。而使用原生的方法进行http请求时，如果不设置超时时间，定时任务的那个线程就会一直等待对方的响应，就会一直处于运行状态处理该任务，等待下个任务到的时候就没有线程运行了。

正常任务执行完毕后线程的状态应该是TIMED_WAITING，在异常的状态下线程的状态却是RUNNABLE，说明上个任务没有执行完毕，线程一直在执行。

执行完毕后正常状态：

执行完毕后异常状态：

错误代码：

@Component
@Log4j2
public class ScheduleTask {@Autowiredprivate SecondUserMapper secondUserMapper;@Scheduled(cron = "0 0/2 * * * ?") //定时任务注解+cron表达式public void testScheduleTask() throws IOException, InterruptedException {List<String> urlList = secondUserMapper.getRandomUrlList();Thread.sleep(3000);for (String s : urlList) {URL url = new URL(s);// 打开连接HttpURLConnection connection = (HttpURLConnection) url.openConnection();// 设置请求方法为GETconnection.setRequestMethod("GET");// 添加自定义的请求头信息String agent = secondUserMapper.getRandomAgent();connection.addRequestProperty("User-Agent", agent);connection.addRequestProperty("Accept-Language", "en-US,en;q=0.9");// 获取服务器返回的状态码int responseCode = connection.getResponseCode();if (responseCode == HttpURLConnection.HTTP_OK) {// 读取服务器返回的数据BufferedReader reader = new BufferedReader(new InputStreamReader(connection.getInputStream()));String line;StringBuilder response = new StringBuilder();while ((line = reader.readLine()) != null) {response.append(line);}reader.close();System.out.println("Server Response:" + responseCode);} else {System.out.println("Error Code: " + responseCode);}// 关闭连接connection.disconnect();}log.info("线程名称为{},线程状态为{}",Thread.currentThread().getName(),Thread.currentThread().getState().name());}
}

正确代码：

增加超时时间即可

@Component
@Log4j2
public class ScheduleTask {@Autowiredprivate SecondUserMapper secondUserMapper;@Scheduled(cron = "0 0/2 * * * ?") //定时任务注解+cron表达式public void testScheduleTask() throws IOException, InterruptedException {List<String> urlList = secondUserMapper.getRandomUrlList();Thread.sleep(3000);for (String s : urlList) {URL url = new URL(s);// 打开连接HttpURLConnection connection = (HttpURLConnection) url.openConnection();// 设置请求方法为GETconnection.setRequestMethod("GET");connection.setConnectTimeout(100000);connection.setReadTimeout(100000);// 添加自定义的请求头信息String agent = secondUserMapper.getRandomAgent();connection.addRequestProperty("User-Agent", agent);connection.addRequestProperty("Accept-Language", "en-US,en;q=0.9");// 获取服务器返回的状态码int responseCode = connection.getResponseCode();if (responseCode == HttpURLConnection.HTTP_OK) {// 读取服务器返回的数据BufferedReader reader = new BufferedReader(new InputStreamReader(connection.getInputStream()));String line;StringBuilder response = new StringBuilder();while ((line = reader.readLine()) != null) {response.append(line);}reader.close();System.out.println("Server Response:" + responseCode);} else {System.out.println("Error Code: " + responseCode);}// 关闭连接connection.disconnect();}log.info("线程名称为{},线程状态为{}",Thread.currentThread().getName(),Thread.currentThread().getState().name());}
}