This article refers to the original- http://bjbsair.com/2020-03-22/tech-info/5100/
order

This paper mainly studies the spring web plus plugin of skywalking

DispatcherHandlerInstrumentation

skywalking-6.6.0/apm-sniffer/optional-plugins/optional-spring-plugins/spring-webflux-5.x-plugin/src/main/java/org/apache/skywalking/apm/plugin/spring/webflux/v5/define/DispatcherHandlerInstrumentation.java

public class DispatcherHandlerInstrumentation extends ClassInstanceMethodsEnhancePluginDefine {  
    @Override  
    public ConstructorInterceptPoint[] getConstructorsInterceptPoints() {  
        return new ConstructorInterceptPoint[0];  
    }  
​  
    @Override  
    public InstanceMethodsInterceptPoint[] getInstanceMethodsInterceptPoints() {  
        return new InstanceMethodsInterceptPoint[]{  
            new InstanceMethodsInterceptPoint() {  
                @Override  
                public ElementMatcher<MethodDescription> getMethodsMatcher() {  
                    return named("handle");  
                }  
​  
                @Override  
                public String getMethodsInterceptor() {  
                    return "org.apache.skywalking.apm.plugin.spring.webflux.v5.DispatcherHandlerHandleMethodInterceptor";  
                }  
​  
                @Override  
                public boolean isOverrideArgs() {  
                    return false;  
                }  
            }  
        };  
    }  
​  
    @Override  
    protected ClassMatch enhanceClass() {  
        return byName("org.springframework.web.reactive.DispatcherHandler");  
    }  
}

• DispatcherHandlerInstrumentation inherits ClassInstanceMethodsEnhancePluginDefine, which uses org.apache.skywalking.apm.plugin.spring.webplus.v5.dispatcherhandlerhandlermethodinterceptor to enhance the handle method of org.springframework.web.reactive.DispatcherHandler

DispatcherHandlerHandleMethodInterceptor

skywalking-6.6.0/apm-sniffer/optional-plugins/optional-spring-plugins/spring-webflux-5.x-plugin/src/main/java/org/apache/skywalking/apm/plugin/spring/webflux/v5/DispatcherHandlerHandleMethodInterceptor.java

public class DispatcherHandlerHandleMethodInterceptor implements InstanceMethodsAroundInterceptor {  
    private static final String DEFAULT_OPERATION_NAME = "WEBFLUX.handle";  
​  
    @Override  
    public void beforeMethod(EnhancedInstance objInst, Method method, Object[] allArguments, Class<?>[] argumentsTypes,  
                             MethodInterceptResult result) throws Throwable {  
​  
    }  
​  
    @Override  
    public Object afterMethod(EnhancedInstance objInst, Method method, Object[] allArguments, Class<?>[] argumentsTypes,  
                              Object ret) throws Throwable {  
        EnhancedInstance instance = getInstance(allArguments[0]);  
​  
        ServerWebExchange exchange = (ServerWebExchange) allArguments[0];  
​  
        ContextCarrier carrier = new ContextCarrier();  
        CarrierItem next = carrier.items();  
        HttpHeaders headers = exchange.getRequest().getHeaders();  
        while (next.hasNext()) {  
            next = next.next();  
            List<String> header = headers.get(next.getHeadKey());  
            if (header != null && header.size() > 0) {  
                next.setHeadValue(header.get(0));  
            }  
        }  
​  
        AbstractSpan span = ContextManager.createEntrySpan(DEFAULT_OPERATION_NAME, carrier);  
        span.setComponent(ComponentsDefine.SPRING_WEBFLUX);  
        SpanLayer.asHttp(span);  
        Tags.URL.set(span, exchange.getRequest().getURI().toString());  
        HTTP.METHOD.set(span, exchange.getRequest().getMethodValue());  
        instance.setSkyWalkingDynamicField(ContextManager.capture());  
        span.prepareForAsync();  
        ContextManager.stopSpan(span);  
​  
        return ((Mono) ret).doFinally(s -> {  
            try {  
                Object pathPattern = exchange.getAttribute(HandlerMapping.BEST_MATCHING_PATTERN_ATTRIBUTE);  
                if (pathPattern != null) {  
                    span.setOperationName(((PathPattern) pathPattern).getPatternString());  
                }  
                HttpStatus httpStatus = exchange.getResponse().getStatusCode();  
                // fix webflux-2.0.0-2.1.0 version have bug. httpStatus is null. not support  
                if (httpStatus != null) {  
                    Tags.STATUS_CODE.set(span, Integer.toString(httpStatus.value()));  
                    if (httpStatus.isError()) {  
                        span.errorOccurred();  
                    }  
                }  
            } finally {  
                span.asyncFinish();  
            }  
        });  
​  
    }  
​  
    @Override  
    public void handleMethodException(EnhancedInstance objInst, Method method, Object[] allArguments,  
                                      Class<?>[] argumentsTypes, Throwable t) {  
    }  
​  
    public static EnhancedInstance getInstance(Object o) {  
        EnhancedInstance instance = null;  
        if (o instanceof DefaultServerWebExchange) {  
            instance = (EnhancedInstance) o;  
        } else if (o instanceof ServerWebExchangeDecorator) {  
            ServerWebExchange delegate = ((ServerWebExchangeDecorator) o).getDelegate();  
            return getInstance(delegate);  
        }  
        return instance;  
    }  
​  
}

• The dispatcherhandlerhandlemethodeinterceptor implements the instancemethods aroundinterceptor interface. Its afterMethod METHOD creates AbstractSpan, sets the tag of URL and METHOD, executes span.prepareForAsync(), registers Mono's doFinally Consumer, sets span's operationName, statusCode, and whether there is an exception, and finally executes span.asyncFinish()

ServerWebExchangeInstrumentation

skywalking-6.6.0/apm-sniffer/optional-plugins/optional-spring-plugins/spring-webflux-5.x-plugin/src/main/java/org/apache/skywalking/apm/plugin/spring/webflux/v5/define/ServerWebExchangeInstrumentation.java

public class ServerWebExchangeInstrumentation extends ClassInstanceMethodsEnhancePluginDefine {  
    @Override  
    public ConstructorInterceptPoint[] getConstructorsInterceptPoints() {  
        return new ConstructorInterceptPoint[]{  
            new ConstructorInterceptPoint() {  
                @Override  
                public ElementMatcher<MethodDescription> getConstructorMatcher() {  
                    return any();  
                }  
​  
                @Override  
                public String getConstructorInterceptor() {  
                    return "org.apache.skywalking.apm.plugin.spring.webflux.v5.ServerWebExchangeConstructorInterceptor";  
                }  
            }  
        };  
    }  
​  
    @Override  
    public InstanceMethodsInterceptPoint[] getInstanceMethodsInterceptPoints() {  
        return new InstanceMethodsInterceptPoint[0];  
    }  
​  
    @Override  
    protected ClassMatch enhanceClass() {  
        return byName("org.springframework.web.server.adapter.DefaultServerWebExchange");  
    }  
}

• Serverwebexchangeinstruction inherits classinstancemethods enhanceplugindefine, which uses org.apache.skywalking.apm.plugin.spring.webplus.v5.serverwebexchangeconstructorinterceptor to enhance all methods of org.springframework.web.server.adapter.DefaultServerWebExchange

ServerWebExchangeConstructorInterceptor

skywalking-6.6.0/apm-sniffer/optional-plugins/optional-spring-plugins/spring-webflux-5.x-plugin/src/main/java/org/apache/skywalking/apm/plugin/spring/webflux/v5/ServerWebExchangeConstructorInterceptor.java

public class ServerWebExchangeConstructorInterceptor implements InstanceConstructorInterceptor {  
    @Override  
    public void onConstruct(EnhancedInstance objInst, Object[] allArguments) {  
    }  
}

• ServerWebExchangeConstructorInterceptor is currently empty

Summary

DispatcherHandlerInstrumentation inherits ClassInstanceMethodsEnhancePluginDefine, which uses org.apache.skywalking.apm.plugin.spring.webplus.v5.dispatcherhandlerhandlermethodinterceptor to enhance the handle method of org.springframework.web.reactive.DispatcherHandler; serverwebexchangeinstruction inherits ClassInstanceMethodsEnhancePluginDefine, which uses Org.apache.skywalking.apm.plugin.spring.webplus.v5.serverwebexchangeconstructorinterceptor enhance all methods of org.springframework.web.server.adapter.DefaultServerWebExchange

doc

• DispatcherHandlerInstrumentation
• ServerWebExchangeInstrumentation