我有InheritableThreadLocal<ConcurrentHashMap<String, Object>>线程，当请求来自过滤器并在其中设置一些transaction_id时初始化。
现在在服务层，我通过CompletableFuture调用10个不同的API调用。所有API服务类都有一个execute方法，该方法使用RestTempate进行API调用。我把@HystrixCommand放在execute方法上。
execute方法是void类型，但它将API响应放在InheritableThreadLocal对象中。
问题是当API调用失败时Hystrix调用FallBackMethod，当我在InheritableThreadLocal中放入错误响应时，我无法将错误响应发送到客户端。
public class ThreadLocalUtil {
private static InheritableThreadLocal<ConcurrentHashMap<String, Object>> transmittableThreadLocal = new InheritableThreadLocal<>();
public static void addDataToThreadLocalMap(String key, Object value) {
Map<String, Object> existingDataMap = transmittableThreadLocal.get();
if (value != null) {
existingDataMap.put(key, value);
}
}
public static Object getDataFromThreadLocalMap(String key) {
Map<String, Object> existingDataMap = transmittableThreadLocal.get();
return existingDataMap.get(key);
}
public static void clearThreadLocalDataMap() {
if (transmittableThreadLocal != null)
transmittableThreadLocal.remove();
}
public static Object getRequestData(String key) {
Map<String, Object> existingDataMap = transmittableThreadLocal.get();
if (existingDataMap != null) {
return existingDataMap.get(key);
}
return "-1";
}
public static void initThreadLocals() {
ConcurrentHashMap<String, Object> dataForDataMap = new ConcurrentHashMap<String, Object>();
String requestId = "REQUEST_ID_" + System.currentTimeMillis();
dataForDataMap.put("REQUEST_ID", requestId);
transmittableThreadLocal.set(dataForDataMap);
}
}
@Component
@Order(1)
public class CommonFilter extends OncePerRequestFilter {
@Override
protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain)
throws ServletException, IOException {
try {
ThreadLocalUtil.initThreadLocals();
filterChain.doFilter(request, response);
} catch (Exception e) {
if (e instanceof ServletException) {
throw (ServletException) e;
}
} finally {
ThreadLocalUtil.clearThreadLocalDataMap();
}
}
@Component
public abstract class EmployeeService {
@Autowired
private ThreadLocalUtil threadLocalUtil;
public abstract void getEmployee(int employeeId);
public void fallbackMethod(int employeeid) {
threadLocalUtil.addDataToThreadLocalMap("ErrorResponse", "Fallback response:: No employee details available temporarily");
}
}
@Service
public class EmployeeServiceImpl extends EmployeeService {
@HystrixCommand(fallbackMethod = "fallbackMethod", commandProperties = {
@HystrixProperty(name = "execution.isolation.thread.timeoutInMilliseconds", value = "900"),
@HystrixProperty(name = "circuitBreaker.errorThresholdPercentage", value = "10") })
public void getEmployee(int employeeId) {
System.out.println("Getting Employee details for " + employeeId + ", threadLocalUtil : " + threadLocalUtil.getDataFromThreadLocalMap("EMPLOYE_ID"));
String response = restTemplate.exchange("http://localhost:8011/findEmployeeDetails/{employeeid}",
HttpMethod.GET, null, new ParameterizedTypeReference<String>() {
}, employeeId).getBody();
threadLocalUtil.addDataToThreadLocalMap("Response", response);
}
@Autowired
RestTemplate restTemplate;
@Autowired
private ThreadLocalUtil threadLocalUtil;
}
所以，首先，因为内部Hystrix使用ThreadPoolExecutor（线程创建一次并重复使用），所以使用InheritableThreadLocal是错误的。
从上面的问题以及你在我的blog中提出的问题，我明白你的问题是
InheritableThreadLocal在hystrix后备方法中变为null
进一步添加到此（您可以验证这一点）
只有在超时的情况下，
InheritableThreadLocal才会在hystrix回退方法中变为null，而在任何其他异常的情况下都不会
我建议其他人参考我的blog。在超时的情况下，Hystrix回退发生在hystrix-timer线程中。 Hystrix fallback execution thread您可以通过记录Thread.currentThread().getName()来验证这一点
由于hystrix-timer thread的父级不是您的调用线程，因此您的transmittableThreadLocal.get（）变为null。
为了解决这个问题，我建议使用HystrixCommandExecutionHook和HystrixRequestVariableDefault。使用它你可以实现像onStart, onExecutionStart, onFallbackStart等钩子，你需要获取/设置threadLocal变量。有关更多详细信息，请参阅博客的最后一部分。
更新：对于您的用例，您可以按如下方式修改代码：
thread local UT IL.Java
public class ThreadLocalUtil {
private static ThreadLocal<ConcurrentHashMap<String, Object>> transmittableThreadLocal = new ThreadLocal<>();
public static ConcurrentHashMap<String, Object> getThreadLocalData() {
return transmittableThreadLocal.get();
}
public static void setThreadLocalData(ConcurrentHashMap<String, Object> data) {
transmittableThreadLocal.set(data);
}
public static void addDataToThreadLocalMap(String key, Object value) {
Map<String, Object> existingDataMap = transmittableThreadLocal.get();
if (value != null) {
existingDataMap.put(key, value);
}
}
public static Object getDataFromThreadLocalMap(String key) {
Map<String, Object> existingDataMap = transmittableThreadLocal.get();
return existingDataMap.get(key);
}
public static void clearThreadLocalDataMap() {
if (transmittableThreadLocal != null)
transmittableThreadLocal.remove();
}
public static Object getRequestData(String key) {
Map<String, Object> existingDataMap = transmittableThreadLocal.get();
if (existingDataMap != null) {
return existingDataMap.get(key);
}
return "-1";
}
public static void initThreadLocals() {
transmittableThreadLocal.set(new ConcurrentHashMap<>());
String requestId = "REQUEST_ID_" + System.currentTimeMillis();
addDataToThreadLocalMap("REQUEST_ID", requestId);
}
}
employee service.Java
@Component
public abstract class EmployeeService {
public abstract void getEmployee(int employeeId);
public void fallbackMethod(int employeeid) {
threadLocalUtil.addDataToThreadLocalMap("ErrorResponse", "Fallback response:: No employee details available temporarily");
}
}
employee service imp了.Java
@Service
public class EmployeeServiceImpl extends EmployeeService {
@HystrixCommand(fallbackMethod = "fallbackMethod", commandProperties = {
@HystrixProperty(name = "execution.isolation.thread.timeoutInMilliseconds", value = "900"),
@HystrixProperty(name = "circuitBreaker.errorThresholdPercentage", value = "10") })
public void getEmployee(int employeeId) {
System.out.println("Getting Employee details for " + employeeId + ", threadLocalUtil : " + threadLocalUtil.getDataFromThreadLocalMap("EMPLOYEE_ID"));
String response = restTemplate.exchange("http://localhost:8011/findEmployeeDetails/{employeeid}",
HttpMethod.GET, null, new ParameterizedTypeReference<String>() {
}, employeeId).getBody();
threadLocalUtil.addDataToThreadLocalMap("Response", response);
}
@Autowired
RestTemplate restTemplate;
}
H YST日系hook.Java
public class HystrixHook extends HystrixCommandExecutionHook {
private HystrixRequestVariableDefault<ConcurrentHashMap<String, Object>> hrv = new HystrixRequestVariableDefault<>();
@Override
public <T> void onStart(HystrixInvokable<T> commandInstance) {
HystrixRequestContext.initializeContext();
getThreadLocals();
}
@Override
public <T> void onExecutionStart(HystrixInvokable<T> commandInstance) {
setThreadLocals();
}
@Override
public <T> void onFallbackStart(HystrixInvokable<T> commandInstance) {
setThreadLocals();
}
@Override
public <T> void onSuccess(HystrixInvokable<T> commandInstance) {
HystrixRequestContext.getContextForCurrentThread().shutdown();
super.onSuccess(commandInstance);
}
@Override
public <T> Exception onError(HystrixInvokable<T> commandInstance, HystrixRuntimeException.FailureType failureType, Exception e) {
HystrixRequestContext.getContextForCurrentThread().shutdown();
return super.onError(commandInstance, failureType, e);
}
private void getThreadLocals() {
hrv.set(ThreadLocalUtil.getThreadLocalData());
}
private void setThreadLocals() {
ThreadLocalUtil.setThreadLocalData(hrv.get());
}
}
ABC application.Java
public class AbcApplication {
public static void main(String[] args) {
HystrixPlugins.getInstance().registerCommandExecutionHook(new HystrixHook());
SpringApplication.run(Abc.class, args);
}
}
希望这可以帮助