dubbo-源码阅读之Filter实现原理

最近完成一个需求,使用阿里Arms需要在log里面加上traceId,但是发现dubbo异常 被ExceptionFilter捕获 并打印  打印不出traceI,然后百度搜索如何重写Filter

参考了这篇文章

https://www.jianshu.com/p/7e7076212bd0

重写ExceptionFilter

1.新增一个dubboExceptionFilter类

标红部分 是我改动电脑 其他都是复制原来的ExceptionFilter

@Activate(
        group = {"provider"}
)
public class ArmsDubboExceptionFilter implements Filter {
    private final Logger logger;

    public ArmsDubboExceptionFilter() {
        this(LoggerFactory.getLogger(ArmsDubboExceptionFilter.class));
    }

    public ArmsDubboExceptionFilter(Logger logger) {
        this.logger = logger;
    }

    public Result invoke(Invoker<?> invoker, Invocation invocation) throws RpcException {
        try {
            setSpan(invocation);
            Result result = invoker.invoke(invocation);
            if (result.hasException() && GenericService.class != invoker.getInterface()) {
                try {
                    Throwable exception = result.getException();
                    if (!(exception instanceof RuntimeException) && exception instanceof Exception) {
                        return result;
                    } else {
                        try {
                            Method method = invoker.getInterface().getMethod(invocation.getMethodName(), invocation.getParameterTypes());
                            Class<?>[] exceptionClassses = method.getExceptionTypes();
                            Class[] arr$ = exceptionClassses;
                            int len$ = exceptionClassses.length;

                            for (int i$ = 0; i$ < len$; ++i$) {
                                Class<?> exceptionClass = arr$[i$];
                                if (exception.getClass().equals(exceptionClass)) {
                                    return result;
                                }
                            }
                        } catch (NoSuchMethodException var11) {
                            return result;
                        }

                        this.logger.error("Got unchecked and undeclared exception which called by " + RpcContext.getContext().getRemoteHost() + ". service: " + invoker.getInterface().getName() + ", method: " + invocation.getMethodName() + ", exception: " + exception.getClass().getName() + ": " + exception.getMessage(), exception);
                        String serviceFile = ReflectUtils.getCodeBase(invoker.getInterface());
                        String exceptionFile = ReflectUtils.getCodeBase(exception.getClass());
                        if (serviceFile != null && exceptionFile != null && !serviceFile.equals(exceptionFile)) {
                            String className = exception.getClass().getName();
                            if (!className.startsWith("java.") && !className.startsWith("javax.")) {
                                return (Result) (exception instanceof RpcException ? result : new RpcResult(new RuntimeException(StringUtils.toString(exception))));
                            } else {
                                return result;
                            }
                        } else {
                            return result;
                        }
                    }
                } catch (Throwable var12) {
                    this.logger.warn("Fail to ExceptionFilter when called by " + RpcContext.getContext().getRemoteHost() + ". service: " + invoker.getInterface().getName() + ", method: " + invocation.getMethodName() + ", exception: " + var12.getClass().getName() + ": " + var12.getMessage(), var12);
                    return result;
                }
            } else {
                return result;
            }
        } catch (RuntimeException var13) {
            this.logger.error("Got unchecked and undeclared exception which called by " + RpcContext.getContext().getRemoteHost() + ". service: " + invoker.getInterface().getName() + ", method: " + invocation.getMethodName() + ", exception: " + var13.getClass().getName() + ": " + var13.getMessage(), var13);
            throw var13;
        } finally {
            ArmsUtils.remove();
        }
    }

    /*
     * 因为通过arms sdk拿不到traceId(与阿里工程师沟通 貌似是bug 暂时自己再协议头里面获取 并存入线程缓存 供log appender使用)
     * @param invocation
     */
    public void setSpan(Invocation invocation) {
        try {
            String sampled = invocation.getAttachment("X-B3-Sampled");
            ArmsUtils.setSpan(invocation.getAttachment("X-B3-TraceId"), invocation.getAttachment("EagleEye-RpcID"), invocation.getAttachment("X-B3-SpanId"), sampled != null && sampled.equals("1"));
        } catch (Exception e) {
            logger.error("写入span异常", e);
        }
    }
}

2.在/src/main/resources/META-INF/dubbo/com.alibaba.dubbo.rpc.Filter新增一个文件com.alibaba.dubbo.rpc.Filter

内容

DubboExceptionFilter=com.biz.core.armslog.ArmsDubboExceptionFilter

3.soa-provider.xml配置

   <!-- 延迟暴露服务,表示延迟到Spring容器初始化完成时暴露服务; 不重试 filter自定义一个dubboExceptionFilter -exception表示替换了默认的ExceptionFilter 增加arms日志打印-->
    <dubbo:provider delay="-1" retries="0" filter="DubboExceptionFilter,-exception"/>

阅读源码 理解为什么这么写

首先需要理解dubbo SPI的实现原理 前一篇有些

ProtocolFilterWrapper

为dubboFilter的包装类 用来为生成filter执行链

/**
     * 为invoker生成filter调用链条 invoker为执行对象
     * @param invoker 执行对象
     * @param key 为参数名
     * @param group 等于@Activate(group = {"provider"})
     * @param <T>
     * @return
     */
    private static <T> Invoker<T> buildInvokerChain(final Invoker<T> invoker, String key, String group) {
        final Invoker<T> last = invoker;
        /**
         * 使用dubbo SPI获取默认和用户自定义的filter
         * url为暴露的服务地址
         * keyinjvm://127.0.0.1/com.biz.soa.service.promotion.backend.OfflineExtend.PromotionOfflineService?anyhost=true&application=soa-promotion-provider&bind.ip=10.37.129.2&bind.port=23888&default.delay=-1&default.retries=0&default.service.filter=DubboExceptionFilter,-exception&delay=-1&dispatcher=message&dubbo=2.6.2&generic=false&interface=com.biz.soa.service.promotion.backend.OfflineExtend.PromotionOfflineService&methods=downLoadPromotion,updaPromotion,queryPromotionOffline,getOfflineProducts,SavePromotion&pid=81391&register=false&side=provider&threadpool=fixed&threads=500&timestamp=1574842487417
         * group为provider (如果是consumer则是consumer)
         * */
        List<Filter> filters = ExtensionLoader.getExtensionLoader(Filter.class).getActivateExtension(invoker.getUrl(), key, group);
        if (!filters.isEmpty()) {
            /**
             * 这里是循环生成filer调用链条  filter1->filter2->invoke
             */
            for(int i = filters.size() - 1; i >= 0; --i) {
                final Filter filter = (Filter)filters.get(i);
                last = new Invoker<T>() {
                    public Class<T> getInterface() {
                        return invoker.getInterface();
                    }

                    public URL getUrl() {
                        return invoker.getUrl();
                    }

                    public boolean isAvailable() {
                        return invoker.isAvailable();
                    }

                    public Result invoke(Invocation invocation) throws RpcException {
                        return filter.invoke(last, invocation);
                    }

                    public void destroy() {
                        invoker.destroy();
                    }

                    public String toString() {
                        return invoker.toString();
                    }
                };
            }
        }

        return last;
    }

ExtensionLoader

ExtensionLoader.getExtensionLoader实现

 /**
     * 根据class获取对应的ExtensionLoader
     * @param type
     * @param <T>
     * @return
     */
    public static <T> ExtensionLoader<T> getExtensionLoader(Class<T> type) {
        if (type == null) {
            throw new IllegalArgumentException("Extension type == null");
        } else if (!type.isInterface()) {
            throw new IllegalArgumentException("Extension type(" + type + ") is not interface!");
        } else if (!withExtensionAnnotation(type)) {
            throw new IllegalArgumentException("Extension type(" + type + ") is not extension, because WITHOUT @" + SPI.class.getSimpleName() + " Annotation!");
        } else {
            //因为是泛型对应的扩展点 提前初始化了一个对应类型的 ExtensionLoader到 这里就会获取到ExtensionLoader<Filter> 的对象
            ExtensionLoader<T> loader = (ExtensionLoader)EXTENSION_LOADERS.get(type);
            if (loader == null) {
                EXTENSION_LOADERS.putIfAbsent(type, new ExtensionLoader(type));
                loader = (ExtensionLoader)EXTENSION_LOADERS.get(type);
            }

            return loader;
        }
    }

ExtensionLoader.getActivateExtension

    /**
     * 获取所有filter 默认的或者用户配置的
     * @param url
     * @param values
     * @param group
     * @return
     */
    public List<T> getActivateExtension(URL url, String[] values, String group) {
        List<T> exts = new ArrayList();
        List<String> names = values == null ? new ArrayList(0) : Arrays.asList(values);
        String name;
        /**
         * 这里是加载默认的filter 如果配置了 -default 将忽略所有默认过滤器
         */
        if (!((List)names).contains("-default")) {
            this.getExtensionClasses();
            Iterator i$ = this.cachedActivates.entrySet().iterator();

            while(i$.hasNext()) {
                Map.Entry<String, Activate> entry = (Map.Entry)i$.next();
                /**
                 * 获得spi配置的key名字 如dubboSPI配置: exception=com.alibaba.dubbo.rpc.filter.ExceptionFilter
                 */
                name = (String)entry.getKey();
                Activate activate = (Activate)entry.getValue();
                /**
                 * 这里匹配Activate的配置的group 只找出provider的
                 */
                if (this.isMatchGroup(group, activate.group())) {
                    T ext = this.getExtension(name);
                    /**
                     * 因为我们配置了-exception  所以这里不会加载                     * isActive如果注解配置了value@Activate(group={"provider"},value={"token"}) 则会在parameter检查是否有传递token 参数 如果有才加入到过滤器
                     */
                    if (!((List)names).contains(name) && !((List)names).contains("-" + name) && this.isActive(activate, url)) {
                        exts.add(ext);
                    }
                }
            }
            /**
             * 排序 可以看ActivateCompartor.COMPARATOR实现 这个排序实现是根据 注解的order 值来排的
             */
            Collections.sort(exts, ActivateComparator.COMPARATOR);
        }
        /**
         * 下面是加载用户的Filter
         * <dubbo:provider delay="-1" retries="0" filter="DubboExceptionFilter,-exception"/>
         */
        List<T> usrs = new ArrayList();

        for(int i = 0; i < ((List)names).size(); ++i) {
            name = (String)((List)names).get(i);
            //-开头的的表示剔除 不执行逻辑
            if (!name.startsWith("-") && !((List)names).contains("-" + name)) {
                if ("default".equals(name)) {
                    if (!usrs.isEmpty()) {
                        exts.addAll(0, usrs);
                        usrs.clear();
                    }
                } else {
                    T ext = this.getExtension(name);
                    usrs.add(ext);
                }
            }
        }

        if (!usrs.isEmpty()) {
            exts.addAll(usrs);
        }

        return exts;
    }

 private boolean isActive(Activate activate, URL url) {
        //获得注解桑的value
        String[] keys = activate.value();
        //如果没有值直接返回true
        if (keys.length == 0) {
            return true;
        } else {
            String[] arr$ = keys;
            int len$ = keys.length;

            label34:
            //遍历values
            for(int i$ = 0; i$ < len$; ++i$) {
                String key = arr$[i$];
                //获得参数列表迭代器 参数列表为xml配置哦
                Iterator i$ = url.getParameters().entrySet().iterator();

                String k;
                String v;
                do {
                    do {
                        if (!i$.hasNext()) {
                            continue label34;
                        }

                        Map.Entry<String, String> entry = (Map.Entry)i$.next();
                        k = (String)entry.getKey();
                        v = (String)entry.getValue();
                        //参数包含了 过滤器信息 同时值不能为空 就加入过滤器
                    } while(!k.equals(key) && !k.endsWith("." + key));
                } while(!ConfigUtils.isNotEmpty(v));

                return true;
            }

            return false;
        }
    }

看完之后是不是一切都明朗了。。我们的com.alibaba.dubbo.rpc.Filter 配置 是SPI实现方式 实现动态注入