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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
代码语言：javascript复制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
代码语言：javascript复制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<MethodDescription> 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
代码语言：javascript复制public class DubboInterceptor implements InstanceMethodsAroundInterceptor {
/**
* <h2>Consumer:</h2> The serialized trace context data will
* inject to the {@link RpcContext#attachments} for transport to provider side.
* <p>
* <h2>Provider:</h2> 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
