InheritableThreadLocal 在线程池中进行父子线程间消息传递出现消息丢失的解析

在日常研发过程中，我们经常面临着需要在线程内，线程间进行消息传递，比如在修改一些开源组件源码的过程中，需要将外部参数透传到内部，如果进行方法参数重载，则涉及到的改动量过大，这样，我们可以依赖ThreadLocal 来进行消息传递。

ThreadLocal 是 存储在线程栈帧中的一块数据存储区域，其可以做到线程与线程之间的读写隔离。

但是在我们的日常场景中，经常会出现 父线程 需要向子线程中传递消息，而 ThreadLocal 仅能在当前线程上进行数据缓存，因此 我们需要使用 InheritableThreadLocal 来实现 父子线程间的消息传递

java;gutter:true; // 定义消息public class ThreadLocalMessage {</p> <pre><code>private final InheritableThreadLocal msg; private ThreadLocalMessage() { msg = new InheritableThreadLocal<>(); } public Msg getMsg() { return this.msg.get(); } public void setMsg(Msg msg) { this.msg.set(msg); } public void clear() { msg.remove(); } private static final ThreadLocalMessage threadLocalMessage = new ThreadLocalMessage(); public static ThreadLocalMessage getInstance() { return threadLocalMessage; } /** * 获取线程中的消息 * * @return */ public static Msg getOrCreateMsg() { Msg msg = ThreadLocalMessage.getInstance().getMsg(); if (msg == null) { msg = new Msg(); } return msg; } public static class Msg { /** * taskId */ private String taskId; private Map others; private int retCode; public Msg() { } public String getTaskId() { return taskId; } public void setTaskId(String taskId) { this.taskId = taskId; } @Override public String toString() { return "Msg{" + "taskId='" + taskId + '\'' + ", others=" + others + ", retCode=" + retCode + '}'; } } </code></pre> <p>}</p> <pre><code> ;gutter:true;
// 定义线程池@EnableAsync
@Configuration
public class ExecutorConfig {

private final Logger log = LoggerFactory.getLogger(getClass());

@Value("${executor.corePool:2}")
private Integer corePool;
@Value("${executor.maxPool:10}")
private Integer maxPool;
@Value("${executor.queue:2}")
private Integer queue;

@Bean("cdl-executor")
public Executor executor() {
log.info("start async Executor");
ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();
//配置核心线程数
executor.setCorePoolSize(corePool);
//配置最大线程数
executor.setMaxPoolSize(maxPool);
//配置队列大小
executor.setQueueCapacity(queue);
//配置线程池中的线程的名称前缀
executor.setThreadNamePrefix("async-executor-");

// 设置拒绝策略
executor.setRejectedExecutionHandler((r, e) -> {
// …..

});

// CALLER_RUNS：不在新线程中执行任务，而是有调用者所在的线程来执行
executor.setRejectedExecutionHandler(new ThreadPoolExecutor.CallerRunsPolicy());
//执行初始化
executor.initialize();
return executor; // 使用TTL 初始化 executor
//return TtlExecutors.getTtlExecutor(executor);
}
}

java;gutter:true; // 创建子线程进行消息传递并打印public String test() throws Exception{ for (int i = 0 ; i < 20; i++){ ThreadLocalMessage.Msg msg = ThreadLocalMessage.getOrCreateMsg(); msg.setTaskId("task_id_"+i); ThreadLocalMessage.getInstance().setMsg(msg); myService.testThread(i); ThreadLocalMessage.getInstance().clear(); } return "ok"; }</p> <pre><code> [TencentCloudSDKException] code:FailedOperation.ServiceIsolate message:service is stopped due to arrears, please recharge your account in Tencent Cloud requestId:dcc6220a-c2a5-41e8-8ce6-aca8faece79f<details><summary>*<font color='gray'>[En]</font>*</summary>*<font color='gray'>[TencentCloudSDKException] code:FailedOperation.ServiceIsolate message:service is stopped due to arrears, please recharge your account in Tencent Cloud requestId:f4c7d4a5-773f-497c-b696-64094317f979</font>*</details> ![InheritableThreadLocal 在线程池中进行父子线程间消息传递出现消息丢失的解析](https://johngo-pic.oss-cn-beijing.aliyuncs.com/articles/20230602/2888789-20220629150811790-1500648858.png) 经过测试，我们发现 只有10个线程 的消息传递成功了，其余10个线程的消息均丢失了，这是什么原因呢。。。 遇到这个问题，我们首先得弄清楚 InheritableThreadLocal 是如何在父子线程间进行消息传递的 InheritableThreadLocal 在父线程创 **建子线程**的时候，会将父线程中InheritableThreadLocal 中存储的数据 拷贝一份 存储到子线程的 InheritableThreadLocal 中 而我们使用的 线程池，线程池是会反复利用线程的，当线程池没有被创建满，每次都是新创建线程，直到线程池创建满了，再需要使用线程就会从线程池中拿已经创建好的线程。 问题就出在这里，由于后面的线程 是从线程池中去捞已经创建好的线程，不会走创建逻辑，也就无法触发 InheritableThreadLocal 中向子线程 拷贝，这也就是为什么 InheritableThreadLocal 合并线程池 使用时，出现了 消息丢失的原因 如何解决？？？？ 阿里巴巴开源的TTL ，用于解决线程池中的父子线程复用，线程数据传递，可以完美解决这个问题 ;gutter:true;
com.alibaba
transmittable-thread-local
2.0.0

java;gutter:true; @EnableAsync @Configuration public class ExecutorConfig {</p> <pre><code>private final Logger log = LoggerFactory.getLogger(getClass()); @Value("${executor.corePool:2}") private Integer corePool; @Value("${executor.maxPool:10}") private Integer maxPool; @Value("${executor.queue:2}") private Integer queue; @Bean("cdl-executor") public Executor executor() { log.info("start async Executor"); ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor(); //配置核心线程数 executor.setCorePoolSize(corePool); //配置最大线程数 executor.setMaxPoolSize(maxPool); //配置队列大小 executor.setQueueCapacity(queue); //配置线程池中的线程的名称前缀 executor.setThreadNamePrefix("async-executor-"); // 设置拒绝策略 executor.setRejectedExecutionHandler((r, e) -> { // ..... }); // CALLER_RUNS：不在新线程中执行任务，而是有调用者所在的线程来执行 executor.setRejectedExecutionHandler(new ThreadPoolExecutor.CallerRunsPolicy()); //执行初始化 executor.initialize(); // 使用TTL 的 executor return TtlExecutors.getTtlExecutor(executor); //return executor; } </code></pre> <p>}</p> <pre><code> ;gutter:true;
public class ThreadLocalMessage {

private final TransmittableThreadLocal msg;

private ThreadLocalMessage() {
msg = new TransmittableThreadLocal<>();
}

public Msg getMsg() {
return this.msg.get();
}

public void setMsg(Msg msg) {
this.msg.set(msg);
}

public void clear() {
msg.remove();
}

private static final ThreadLocalMessage threadLocalMessage = new ThreadLocalMessage();

public static ThreadLocalMessage getInstance() {
return threadLocalMessage;
}

/**
* 获取线程中的消息
*
* @return
*/
public static Msg getOrCreateMsg() {
Msg msg = ThreadLocalMessage.getInstance().getMsg();
if (msg == null) {
msg = new Msg();
}
return msg;
}

public static class Msg {

/**
* taskId
*/
private String taskId;

public Msg() {
}

public String getTaskId() {
return taskId;
}

public void setTaskId(String taskId) {
this.taskId = taskId;
}

@Override
public String toString() {
return "Msg{" +
"taskId=’" + taskId + ‘\” +
‘}’;
}
}

}

[TencentCloudSDKException] code:FailedOperation.ServiceIsolate message:service is stopped due to arrears, please recharge your account in Tencent Cloud requestId:34d855e8-6e2e-422b-bd41-f74d4e8f42b1

[TencentCloudSDKException] code:FailedOperation.ServiceIsolate message:service is stopped due to arrears, please recharge your account in Tencent Cloud requestId:d8d6fcaa-1473-4504-adc2-4b044dc95cdf

Original: https://www.cnblogs.com/hujunhui530/p/16423851.html
Author: applogize
Title: InheritableThreadLocal 在线程池中进行父子线程间消息传递出现消息丢失的解析