Feign calls lost Header solutions

No. article first appeared in public, "the programmer fruit"
Address: https://mp.weixin.qq.com/s/a99TeOxgZGNgFkpT6gmA3g

problem

In Spring Cloud call between micro service uses Feign, but by default, Feign calls exist Header remote service request header loss problems.

solution

Feign first need to write a request interceptor, by implementing RequestInterceptor interface for all Feign completion request, transmitting the request header and request parameters.

Feign request interceptor

public class FeignBasicAuthRequestInterceptor implements RequestInterceptor {

    private static final Logger logger = LoggerFactory.getLogger(FeignBasicAuthRequestInterceptor.class);

    @Override
    public void apply(RequestTemplate requestTemplate) {
        ServletRequestAttributes attributes = (ServletRequestAttributes) RequestContextHolder
                .getRequestAttributes();
        HttpServletRequest request = attributes.getRequest();
        Enumeration<String> headerNames = request.getHeaderNames();
        if (headerNames != null) {
            while (headerNames.hasMoreElements()) {
                String name = headerNames.nextElement();
                String values = request.getHeader(name);
                requestTemplate.header(name, values);
            }
        }
        Enumeration<String> bodyNames = request.getParameterNames();
        StringBuffer body =new StringBuffer();
        if (bodyNames != null) {
            while (bodyNames.hasMoreElements()) {
                String name = bodyNames.nextElement();
                String values = request.getParameter(name);
                body.append(name).append("=").append(values).append("&");
            }
        }
        if(body.length()!=0) {
            body.deleteCharAt(body.length()-1);
            requestTemplate.body(body.toString());
            logger.info("feign interceptor body:{}",body.toString());
        }
    }
}

Configuration via configuration files for all FeignClientto useFeignBasicAuthRequestInterceptor

feign:
  client:
    config:
      default:
        connectTimeout: 5000
        readTimeout: 5000
        loggerLevel: basic
        requestInterceptors: com.leparts.config.FeignBasicAuthRequestInterceptor

You can also be configured so that one FeignClientto use thisFeignBasicAuthRequestInterceptor

feign:
  client:
    config:
      xxxx: # 远程服务名
        connectTimeout: 5000
        readTimeout: 5000
        loggerLevel: basic
        requestInterceptors: com.leparts.config.FeignBasicAuthRequestInterceptor

After testing, the above solution can be normal use; but there is a new problem.

Feign when forwarding the request header, if opened Hystrix, Hystrix default isolation strategy Thread (thread isolation strategy), and therefore can not be forwarded within the interceptor to obtain the requested information in the request header.

You can modify the default policy for semaphore isolation mode:

hystrix.command.default.execution.isolation.strategy=SEMAPHORE

But semaphore isolation mode is not officially recommended strategies; Another solution is to customize Hystrix isolation policies.

Custom Policy

HystrixConcurrencyStrategy is available to developers to customize its internal thread pool queue hystrix, callable also provided a method of packaging, and the transmission context variables. So you can inherit HystrixConcurrencyStrategy, to achieve their concurrency strategy.

@Component
public class FeignHystrixConcurrencyStrategy extends HystrixConcurrencyStrategy {

    private static final Logger log = LoggerFactory.getLogger(FeignHystrixConcurrencyStrategy.class);

    private HystrixConcurrencyStrategy delegate;

    public FeignHystrixConcurrencyStrategy() {
        try {
            this.delegate = HystrixPlugins.getInstance().getConcurrencyStrategy();
            if (this.delegate instanceof FeignHystrixConcurrencyStrategy) {
                // 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 instance = HystrixPlugins.getInstance();
            instance.registerConcurrencyStrategy(this);
            instance.registerCommandExecutionHook(commandExecutionHook);
            instance.registerEventNotifier(eventNotifier);
            instance.registerMetricsPublisher(metricsPublisher);
            instance.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 <T> Callable<T> wrapCallable(Callable<T> callable) {
        RequestAttributes requestAttributes = RequestContextHolder.getRequestAttributes();
        return new WrappedCallable<>(callable, requestAttributes);
    }

    @Override
    public ThreadPoolExecutor getThreadPool(HystrixThreadPoolKey threadPoolKey,
                                            HystrixProperty<Integer> corePoolSize,
                                            HystrixProperty<Integer> maximumPoolSize,
                                            HystrixProperty<Integer> keepAliveTime,
                                            TimeUnit unit, BlockingQueue<Runnable> 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<Runnable> getBlockingQueue(int maxQueueSize) {
        return this.delegate.getBlockingQueue(maxQueueSize);
    }

    @Override
    public <T> HystrixRequestVariable<T> getRequestVariable(HystrixRequestVariableLifecycle<T> rv) {
        return this.delegate.getRequestVariable(rv);
    }

    static class WrappedCallable<T> implements Callable<T> {
        private final Callable<T> target;
        private final RequestAttributes requestAttributes;

        WrappedCallable(Callable<T> 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();
            }
        }
    }
}

Of this, Feign call request is missing the problem head on a resolved.

reference

https://blog.csdn.net/zl1zl2zl3/article/details/79084368
https://cloud.spring.io/spring-cloud-static/spring-cloud-openfeign/2.2.0.RC2/reference/html/

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