多租户 TransmittableThreadLocal 线程安全问题-编程知识

多租户 TransmittableThreadLocal 线程安全问题

在一个多租户项目中，用户登录时,会在自定义请求头拦截器AsyncHandlerInterceptor将该用户的userId,cstNo等用户信息设置到TransmittableThreadLocal中,在后续代码中使用.代码如下:

HeaderInterceptor 请求头拦截器


public class HeaderInterceptor implements AsyncHandlerInterceptor
{@Overridepublic boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception{if (!(handler instanceof HandlerMethod)){return true;}SecurityContextHolder.setUserId(ServletUtils.getHeader(request, SecurityConstants.DETAILS_USER_ID));SecurityContextHolder.setUserName(ServletUtils.getHeader(request, SecurityConstants.DETAILS_USERNAME));SecurityContextHolder.setUserKey(ServletUtils.getHeader(request, SecurityConstants.USER_KEY));SecurityContextHolder.setCstNoKey(ServletUtils.getHeader(request, SecurityConstants.CST_NO));String token = SecurityUtils.getToken();if (StringUtils.isNotEmpty(token)){LoginUser loginUser = AuthUtil.getLoginUser(token);if (StringUtils.isNotNull(loginUser)){AuthUtil.verifyLoginUserExpire(loginUser);SecurityContextHolder.set(SecurityConstants.LOGIN_USER, loginUser);}}return true;}@Overridepublic void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex)throws Exception{SecurityContextHolder.remove();}
}

SecurityContextHolder


public class SecurityContextHolder
{private static final TransmittableThreadLocal<Map<String, Object>> THREAD_LOCAL = new TransmittableThreadLocal<>();public static void set(String key, Object value){Map<String, Object> map = getLocalMap();map.put(key, value == null ? StringUtils.EMPTY : value);}public static String get(String key){Map<String, Object> map = getLocalMap();return Convert.toStr(map.getOrDefault(key, StringUtils.EMPTY));}public static <T> T get(String key, Class<T> clazz){Map<String, Object> map = getLocalMap();return StringUtils.cast(map.getOrDefault(key, null));}public static Map<String, Object> getLocalMap(){Map<String, Object> map = THREAD_LOCAL.get();if (map == null){map = new ConcurrentHashMap<String, Object>();THREAD_LOCAL.set(map);}return map;}public static void setLocalMap(Map<String, Object> threadLocalMap){THREAD_LOCAL.set(threadLocalMap);}public static void setCstNoKey(String cstNoKey){set(SecurityConstants.CST_NO, cstNoKey);}public static String getCstNo(){return Convert.toStr(get(SecurityConstants.CST_NO), null);}public static Long getUserId(){return Convert.toLong(get(SecurityConstants.DETAILS_USER_ID), 0L);}public static void setUserId(String account){set(SecurityConstants.DETAILS_USER_ID, account);}public static String getUserName(){return get(SecurityConstants.DETAILS_USERNAME);}public static void setUserName(String username){set(SecurityConstants.DETAILS_USERNAME, username);}public static String getUserKey(){return get(SecurityConstants.USER_KEY);}public static void setUserKey(String userKey){set(SecurityConstants.USER_KEY, userKey);}public static String getPermission(){return get(SecurityConstants.ROLE_PERMISSION);}public static void setPermission(String permissions){set(SecurityConstants.ROLE_PERMISSION, permissions);}public static void remove(){THREAD_LOCAL.remove();}}

在业务层通过调用多线程方法时,分别在主线程和子线程中输出客户编号,伪代码如下:

public void listMasterThread() {log.info(">>>>>>>>>>>主线程{}>>>>>", SecurityContextHolder.getCstNo());
CompletableFuture.supplyAsync(() -> this.savleThread(),threadPoolConfig.threadPool())}public void savleThread(){log.info(">>>>>>>>>>>子线程{}>>>>>", SecurityContextHolder.getCstNo());
}

问题复现:
客户编号为85的员工先登录(第一次登录)并调用该方法时,输出如下:

>>>>>>>>>>>主线程85 >>>>>
>>>>>>>>>>>子线程85 >>>>>

接着客户编号82的员工接着登录(第二次登录)并调用时,输出:

>>>>>>>>>>>主线程82 >>>>>
>>>>>>>>>>>子线程85 >>>>>

问题就来了,第二次登录时,主线程获取的客户编号正确,但是子线程获取的客户编号是上一次登录,并且多调用几次之后,子线程的输出也正常了.

下面是TransmittableThreadLocal.get()方法源码,最终调用的是ThreadLocal.get()
在这里插入图片描述
百度了一下TransmittableThreadLocal 用于解决 “在使用线程池会缓存线程的组件情况下传递ThreadLocal”问题的.

到这里就很疑惑,明明用的就是 TransmittableThreadLocal但是为何还会有此问题,经过折腾

解决方法添加TtlExecutors.getTtlExecutor()

	// threadPoolConfig.threadPool() 参数为指定的线程池TtlExecutors.getTtlExecutor(threadPoolConfig.threadPool());

纠正后的伪代码如下,

public void listMasterThread() {log.info(">>>>>>>>>>>主线程{}>>>>>", SecurityContextHolder.getCstNo());TtlExecutors.getTtlExecutor(threadPoolConfig.threadPool());
CompletableFuture.supplyAsync(() -> this.savleThread(),threadPoolConfig.threadPool())}public void savleThread(){log.info(">>>>>>>>>>>子线程{}>>>>>", SecurityContextHolder.getCstNo());
}