聊聊skywalking的dubbo-2.7.x-plugin

序

本文主要研究一下skywalking的dubbo-2.7.x-plugin

skywalking-plugin.def

skywalking-6.6.0/apm-sniffer/apm-sdk-plugin/dubbo-2.7.x-plugin/src/main/resources/skywalking-plugin.def

dubbo=org.apache.skywalking.apm.plugin.asf.dubbo.DubboInstrumentation

• skywalking的dubbo-plugin提供了DubboInstrumentation增强

DubboInstrumentation

skywalking-6.6.0/apm-sniffer/apm-sdk-plugin/dubbo-2.7.x-plugin/src/main/java/org/apache/skywalking/apm/plugin/asf/dubbo/DubboInstrumentation.java

public class DubboInstrumentation extends ClassInstanceMethodsEnhancePluginDefine {

    private static final String ENHANCE_CLASS = "org.apache.dubbo.monitor.support.MonitorFilter";

    private static final String INTERCEPT_CLASS = "org.apache.skywalking.apm.plugin.asf.dubbo.DubboInterceptor";

    @Override
    protected ClassMatch enhanceClass() {
        return NameMatch.byName(ENHANCE_CLASS);
    }

    @Override
    public ConstructorInterceptPoint[] getConstructorsInterceptPoints() {
        return null;
    }

    @Override
    public InstanceMethodsInterceptPoint[] getInstanceMethodsInterceptPoints() {
        return new InstanceMethodsInterceptPoint[] {
            new InstanceMethodsInterceptPoint() {
                @Override
                public ElementMatcher getMethodsMatcher() {
                    return named("invoke");
                }

                @Override
                public String getMethodsInterceptor() {
                    return INTERCEPT_CLASS;
                }

                @Override
                public boolean isOverrideArgs() {
                    return false;
                }
            }
        };
    }
}

• DubboInstrumentation继承了ClassInstanceMethodsEnhancePluginDefine，它使用org.apache.skywalking.apm.plugin.asf.dubbo.DubboInterceptor来增强org.apache.dubbo.monitor.support.MonitorFilter的invoke方法

DubboInterceptor

skywalking-6.6.0/apm-sniffer/apm-sdk-plugin/dubbo-2.7.x-plugin/src/main/java/org/apache/skywalking/apm/plugin/asf/dubbo/DubboInterceptor.java

public class DubboInterceptor implements InstanceMethodsAroundInterceptor {
    /**
     * 
Consumer:
 The serialized trace context data will
     * inject to the {@link RpcContext#attachments} for transport to provider side.
     * 

     * 
Provider:
 The serialized trace context data will extract from
     * {@link RpcContext#attachments}. current trace segment will ref if the serialize context data is not null.
     */
    @Override
    public void beforeMethod(EnhancedInstance objInst, Method method, Object[] allArguments,
        Class[] argumentsTypes, MethodInterceptResult result) throws Throwable {
        Invoker invoker = (Invoker)allArguments[0];
        Invocation invocation = (Invocation)allArguments[1];
        RpcContext rpcContext = RpcContext.getContext();
        boolean isConsumer = rpcContext.isConsumerSide();
        URL requestURL = invoker.getUrl();

        AbstractSpan span;

        final String host = requestURL.getHost();
        final int port = requestURL.getPort();
        if (isConsumer) {
            final ContextCarrier contextCarrier = new ContextCarrier();
            span = ContextManager.createExitSpan(generateOperationName(requestURL, invocation), contextCarrier, host + ":" + port);
            //invocation.getAttachments().put("contextData", contextDataStr);
            //@see https://github.com/alibaba/dubbo/blob/dubbo-2.5.3/dubbo-rpc/dubbo-rpc-api/src/main/java/com/alibaba/dubbo/rpc/RpcInvocation.java#L154-L161
            CarrierItem next = contextCarrier.items();
            while (next.hasNext()) {
                next = next.next();
                rpcContext.getAttachments().put(next.getHeadKey(), next.getHeadValue());
            }
        } else {
            ContextCarrier contextCarrier = new ContextCarrier();
            CarrierItem next = contextCarrier.items();
            while (next.hasNext()) {
                next = next.next();
                next.setHeadValue(rpcContext.getAttachment(next.getHeadKey()));
            }

            span = ContextManager.createEntrySpan(generateOperationName(requestURL, invocation), contextCarrier);
        }

        Tags.URL.set(span, generateRequestURL(requestURL, invocation));
        span.setComponent(ComponentsDefine.DUBBO);
        SpanLayer.asRPCFramework(span);
    }

    @Override
    public Object afterMethod(EnhancedInstance objInst, Method method, Object[] allArguments,
        Class[] argumentsTypes, Object ret) throws Throwable {
        Result result = (Result)ret;
        if (result != null && result.getException() != null) {
            dealException(result.getException());
        }

        ContextManager.stopSpan();
        return ret;
    }

    @Override
    public void handleMethodException(EnhancedInstance objInst, Method method, Object[] allArguments,
        Class[] argumentsTypes, Throwable t) {
        dealException(t);
    }

    /**
     * Log the throwable, which occurs in Dubbo RPC service.
     */
    private void dealException(Throwable throwable) {
        AbstractSpan span = ContextManager.activeSpan();
        span.errorOccurred();
        span.log(throwable);
    }

    /**
     * Format operation name. e.g. org.apache.skywalking.apm.plugin.test.Test.test(String)
     *
     * @return operation name.
     */
    private String generateOperationName(URL requestURL, Invocation invocation) {
        StringBuilder operationName = new StringBuilder();
        operationName.append(requestURL.getPath());
        operationName.append("." + invocation.getMethodName() + "(");
        for (Class classes : invocation.getParameterTypes()) {
            operationName.append(classes.getSimpleName() + ",");
        }

        if (invocation.getParameterTypes().length > 0) {
            operationName.delete(operationName.length() - 1, operationName.length());
        }

        operationName.append(")");

        return operationName.toString();
    }

    /**
     * Format request url.
     * e.g. dubbo://127.0.0.1:20880/org.apache.skywalking.apm.plugin.test.Test.test(String).
     *
     * @return request url.
     */
    private String generateRequestURL(URL url, Invocation invocation) {
        StringBuilder requestURL = new StringBuilder();
        requestURL.append(url.getProtocol() + "://");
        requestURL.append(url.getHost());
        requestURL.append(":" + url.getPort() + "/");
        requestURL.append(generateOperationName(url, invocation));
        return requestURL.toString();
    }
}

• DubboInterceptor实现了InstanceMethodsAroundInterceptor接口，其beforeMethod方法针对consumer端会将contextCarrier.items()通过rpcContext的attachment来传递，针对provider端会从rpcContext的attachment取出contextCarrier.items()的值，最后设置url的tag，执行SpanLayer.asRPCFramework(span)；其afterMethod方法会执行ContextManager.stopSpan()，并在result.getException()不为null时执行dealException；handleMethodException方法执行dealException；dealException方法主要是执行span.errorOccurred()及span.log(throwable)

小结

DubboInstrumentation继承了ClassInstanceMethodsEnhancePluginDefine，它使用org.apache.skywalking.apm.plugin.asf.dubbo.DubboInterceptor来增强org.apache.dubbo.monitor.support.MonitorFilter的invoke方法

doc

• DubboInstrumentation
• DubboInterceptor