微服务开发中经常有这样的需求，公司自定义了通用的请求头，需要在微服务的调用链中转发，比如在请求头中加入了token，或者某个自定义的信息uniqueId，总之就是自定义的一个键值对的东东，A服务调用B服务，B服务调用C服务，这样通用的东西如何让他在一个调用链中不断地传递下去呢？以A服务为例：
方案1
最傻的办法，在程序中获取，调用B的时候再转发，怎么获取在Controller中国通过注解获取，或者通过request对象获取，这个不难，在请求B服务的时候，通过注解将值放进去即可；简代码如下：
获取：
@RequestMapping(value = "/api/test", method = RequestMethod.GET)
public String testFun(@RequestParam String name, @RequestHeader("uniqueId") String uniqueId) {
if(uniqueId == null ){
return "Must defined the uniqueId , it can not be null";
}
log.info(uniqueId, "begin testFun... ");
return uniqueId;
}
然后A使用Feign调用B服务的时候，传过去：
@FeignClient(value = "DEMO-SERVICE")
public interface CallClient {
@RequestMapping(value = "/api/test", method = RequestMethod.GET)
String callApiTest(@RequestParam(value = "name") String name, @RequestHeader(value = "uniqueId") String uniqueId);
}
方案弊端：毫无疑问，这方案不好，因为对代码有侵入，需要开发人员没次手动的获取和添加，因此舍弃
方案2
服务通过请求拦截器，在请求从A发送到B之后，在拦截器内将自己需要的东东加到请求头：
import com.intellif.log.LoggerUtilI;
import feign.RequestInterceptor;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.context.request.RequestContextHolder;
import org.springframework.web.context.request.ServletRequestAttributes;
import javax.servlet.http.HttpServletRequest;
import java.util.Enumeration;
@Configuration
public class FeignHeadConfiguration {
private final LoggerUtilI logger = LoggerUtilI.getLogger(this.getClass().getName());
@Bean
public RequestInterceptor requestInterceptor() {
return requestTemplate -> {
ServletRequestAttributes attrs = (ServletRequestAttributes) RequestContextHolder.getRequestAttributes();
if (attrs != null) {
HttpServletRequest request = attrs.getRequest();
Enumeration headerNames = request.getHeaderNames();
if (headerNames != null) {
while (headerNames.hasMoreElements()) {
String name = headerNames.nextElement();
String value = request.getHeader(name);
if ("uniqueId".equalsIgnoreCase(name) || "token".equalsIgnoreCase(name)) {
logger.debug("添加自定义请求头key:" + name + ",value:" + value);
requestTemplate.header(name, value);
} else {
logger.debug("FeignHeadConfiguration", "非自定义请求头key:" + name + ",value:" + value + "不需要添加!");
}
}
} else {
logger.warn("FeignHeadConfiguration", "获取请求头失败！");
}
}
};
}
}
网上很多关于这种方法的博文或者资料，大同小异，但是有一个问题，在开启熔断器之后，这里的attrs就是null，因为熔断器默认的隔离策略是thread，也就是线程隔离，实际上接收到的对象和这个在发送给B不是一个线程，怎么办？有一个办法，修改隔离策略hystrix.command.default.execution.isolation.strategy=SEMAPHORE，改为信号量的隔离模式，但是不推荐，因为thread是默认的，而且要命的是信号量模式，熔断器不生效，比如设置了熔断时间hystrix.command.default.execution.isolation.semaphore.timeoutInMilliseconds=5000，五秒，如果B服务里面sleep了10秒，非得等到B执行完毕再返回，因此这个方案也不可取；但是有什么办法可以在默认的Thread模式下让拦截器拿到上游服务的请求头？自定义策略：代码如下：
import com.netflix.hystrix.HystrixThreadPoolKey;
import com.netflix.hystrix.HystrixThreadPoolProperties;
import com.netflix.hystrix.strategy.HystrixPlugins;
import com.netflix.hystrix.strategy.concurrency.HystrixConcurrencyStrategy;
import com.netflix.hystrix.strategy.concurrency.HystrixRequestVariable;
import com.netflix.hystrix.strategy.concurrency.HystrixRequestVariableLifecycle;
import com.netflix.hystrix.strategy.eventnotifier.HystrixEventNotifier;
import com.netflix.hystrix.strategy.executionhook.HystrixCommandExecutionHook;
import com.netflix.hystrix.strategy.metrics.HystrixMetricsPublisher;
import com.netflix.hystrix.strategy.properties.HystrixPropertiesStrategy;
import com.netflix.hystrix.strategy.properties.HystrixProperty;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Component;
import org.springframework.web.context.request.RequestAttributes;
import org.springframework.web.context.request.RequestContextHolder;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.Callable;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
@Component
public class FeignHystrixConcurrencyStrategyIntellif extends HystrixConcurrencyStrategy {
private static final Logger log = LoggerFactory.getLogger(FeignHystrixConcurrencyStrategyIntellif.class);
private HystrixConcurrencyStrategy delegate;
public FeignHystrixConcurrencyStrategyIntellif() {
try {
this.delegate = HystrixPlugins.getInstance().getConcurrencyStrategy();
if (this.delegate instanceof FeignHystrixConcurrencyStrategyIntellif) {
// Welcome to singleton hell...
return;
}
HystrixCommandExecutionHook commandExecutionHook =
HystrixPlugins.getInstance().getCommandExecutionHook();
HystrixEventNotifier eventNotifier = HystrixPlugins.getInstance().getEventNotifier();
HystrixMetricsPublisher metricsPublisher = HystrixPlugins.getInstance().getMetricsPublisher();
HystrixPropertiesStrategy propertiesStrategy =
HystrixPlugins.getInstance().getPropertiesStrategy();
this.logCurrentStateOfHystrixPlugins(eventNotifier, metricsPublisher, propertiesStrategy);
HystrixPlugins.reset();
HystrixPlugins.getInstance().registerConcurrencyStrategy(this);
HystrixPlugins.getInstance().registerCommandExecutionHook(commandExecutionHook);
HystrixPlugins.getInstance().registerEventNotifier(eventNotifier);
HystrixPlugins.getInstance().registerMetricsPublisher(metricsPublisher);
HystrixPlugins.getInstance().registerPropertiesStrategy(propertiesStrategy);
} catch (Exception e) {
log.error("Failed to register Sleuth Hystrix Concurrency Strategy", e);
}
}
private void logCurrentStateOfHystrixPlugins(HystrixEventNotifier eventNotifier,
HystrixMetricsPublisher metricsPublisher, HystrixPropertiesStrategy propertiesStrategy) {
if (log.isDebugEnabled()) {
log.debug("Current Hystrix plugins configuration is [" + "concurrencyStrategy ["
+ this.delegate + "]," + "eventNotifier [" + eventNotifier + "]," + "metricPublisher ["
+ metricsPublisher + "]," + "propertiesStrategy [" + propertiesStrategy + "]," + "]");
log.debug("Registering Sleuth Hystrix Concurrency Strategy.");
}
}
@Override
public Callable wrapCallable(Callable callable) {
RequestAttributes requestAttributes = RequestContextHolder.getRequestAttributes();
return new WrappedCallable<>(callable, requestAttributes);
}
@Override
public ThreadPoolExecutor getThreadPool(HystrixThreadPoolKey threadPoolKey,
HystrixProperty corePoolSize, HystrixProperty maximumPoolSize,
HystrixProperty keepAliveTime, TimeUnit unit, BlockingQueue workQueue) {
return this.delegate.getThreadPool(threadPoolKey, corePoolSize, maximumPoolSize, keepAliveTime,
unit, workQueue);
}
@Override
public ThreadPoolExecutor getThreadPool(HystrixThreadPoolKey threadPoolKey,
HystrixThreadPoolProperties threadPoolProperties) {
return this.delegate.getThreadPool(threadPoolKey, threadPoolProperties);
}
@Override
public BlockingQueue getBlockingQueue(int maxQueueSize) {
return this.delegate.getBlockingQueue(maxQueueSize);
}
@Override
public HystrixRequestVariable getRequestVariable(HystrixRequestVariableLifecycle rv) {
return this.delegate.getRequestVariable(rv);
}
static class WrappedCallable implements Callable {
private final Callable target;
private final RequestAttributes requestAttributes;
public WrappedCallable(Callable target, RequestAttributes requestAttributes) {
this.target = target;
this.requestAttributes = requestAttributes;
}
@Override
public T call() throws Exception {
try {
RequestContextHolder.setRequestAttributes(requestAttributes);
return target.call();
} finally {
RequestContextHolder.resetRequestAttributes();
}
}
}
}
然后使用默认的熔断器隔离策略，也可以在拦截器内获取到上游服务的请求头信息了；
这里参考的博客，感谢这位大牛：https://blog.csdn.net/Crystalqy/article/details/79083857
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