序

本文主要研究一下skywalking的log4j2-activation

skywalking-plugin.def

skywalking-6.6.0/apm-sniffer/apm-toolkit-activation/apm-toolkit-log4j-2.x-activation/src/main/resources/skywalking-plugin.def

toolkit-log4j2=org.apache.skywalking.apm.toolkit.activation.log.log4j.v2.x.TraceIdConverterActivation
toolkit-log4j2=org.apache.skywalking.apm.toolkit.activation.log.log4j.v2.x.async.AsyncLoggerConfigInstrumentation
toolkit-log4j2=org.apache.skywalking.apm.toolkit.activation.log.log4j.v2.x.async.Log4jLogEventInstrumentation
toolkit-log4j2=org.apache.skywalking.apm.toolkit.activation.log.log4j.v2.x.async.RingBufferLogEventInstrumentation

• skywalking的log4j2-activation定义了TraceIdConverterActivation、AsyncLoggerConfigInstrumentation、Log4jLogEventInstrumentation、RingBufferLogEventInstrumentation这几个增强

TraceIdConverterActivation

skywalking-6.6.0/apm-sniffer/apm-toolkit-activation/apm-toolkit-log4j-2.x-activation/src/main/java/org/apache/skywalking/apm/toolkit/activation/log/log4j/v2/x/TraceIdConverterActivation.java

public class TraceIdConverterActivation extends ClassInstanceMethodsEnhancePluginDefine {

    private static final String INTERCEPT_CLASS = "org.apache.skywalking.apm.toolkit.activation.log.log4j.v2.x.TraceIdConverterMethodInterceptor";
    private static final String ENHANCE_CLASS = "org.apache.skywalking.apm.toolkit.log.log4j.v2.x.TraceIdConverter";
    private static final String ENHANCE_METHOD = "format";

    @Override
    public ConstructorInterceptPoint[] getConstructorsInterceptPoints() {
        return new ConstructorInterceptPoint[0];
    }

    @Override
    public InstanceMethodsInterceptPoint[] getInstanceMethodsInterceptPoints() {
        return new InstanceMethodsInterceptPoint[]{
            new InstanceMethodsInterceptPoint() {
                @Override
                public ElementMatcher<MethodDescription> getMethodsMatcher() {

                    return named(ENHANCE_METHOD);
                }

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

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

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

• TraceIdConverterActivation继承了ClassInstanceMethodsEnhancePluginDefine，它使用org.apache.skywalking.apm.toolkit.activation.log.log4j.v2.x.TraceIdConverterMethodInterceptor增强了org.apache.skywalking.apm.toolkit.log.log4j.v2.x.TraceIdConverter的format方法

TraceIdConverterMethodInterceptor

skywalking-6.6.0/apm-sniffer/apm-toolkit-activation/apm-toolkit-log4j-2.x-activation/src/main/java/org/apache/skywalking/apm/toolkit/activation/log/log4j/v2/x/TraceIdConverterMethodInterceptor.java

public class TraceIdConverterMethodInterceptor implements InstanceMethodsAroundInterceptor {


    @Override
    public void beforeMethod(EnhancedInstance objInst, Method method, Object[] allArguments, Class<?>[] argumentsTypes,
                             MethodInterceptResult result) throws Throwable {
        String tid = "";

        //Async Thread, where ContextManager is not active
        if (!ContextManager.isActive() && allArguments[0] instanceof EnhancedInstance) {
            tid = (String) ((EnhancedInstance) allArguments[0]).getSkyWalkingDynamicField();
            if (tid == null) {
                tid = "N/A";
            }
        } else {
            tid = ContextManager.getGlobalTraceId();
        }
        ((StringBuilder) allArguments[1]).append("TID: ").append(tid);
        result.defineReturnValue(null);
    }

    @Override
    public Object afterMethod(EnhancedInstance objInst, Method method, Object[] allArguments,
                              Class<?>[] argumentsTypes, Object ret) throws Throwable {
        return ret;
    }

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

• TraceIdConverterMethodInterceptor实现了InstanceMethodsAroundInterceptor接口，其beforeMethod方法主要是从ContextManager.getGlobalTraceId()获取tid，然后给allArguments[1]添加TID:前缀的tid值

AsyncLoggerConfigInstrumentation

skywalking-6.6.0/apm-sniffer/apm-toolkit-activation/apm-toolkit-log4j-2.x-activation/src/main/java/org/apache/skywalking/apm/toolkit/activation/log/log4j/v2/x/async/AsyncLoggerConfigInstrumentation.java

public class AsyncLoggerConfigInstrumentation extends ClassInstanceMethodsEnhancePluginDefine {

    private static final String INTERCEPT_CLASS = "org.apache.skywalking.apm.toolkit.activation.log.log4j.v2.x.async.AsyncLoggerConfigMethodInterceptor";
    private static final String ENHANCE_CLASS = "org.apache.logging.log4j.core.async.AsyncLoggerConfig";
    private static final String ENHANCE_METHOD = "populateLazilyInitializedFields";

    @Override
    public ConstructorInterceptPoint[] getConstructorsInterceptPoints() {
        return new ConstructorInterceptPoint[0];
    }

    @Override
    public InstanceMethodsInterceptPoint[] getInstanceMethodsInterceptPoints() {
        return new InstanceMethodsInterceptPoint[]{
            new InstanceMethodsInterceptPoint() {
                @Override
                public ElementMatcher<MethodDescription> getMethodsMatcher() {
                    return named(ENHANCE_METHOD);
                }

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

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

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

• AsyncLoggerConfigInstrumentation继承了ClassInstanceMethodsEnhancePluginDefine，它使用org.apache.skywalking.apm.toolkit.activation.log.log4j.v2.x.async.AsyncLoggerConfigMethodInterceptor增强了org.apache.logging.log4j.core.async.AsyncLoggerConfig的populateLazilyInitializedFields方法

AsyncLoggerConfigMethodInterceptor

skywalking-6.6.0/apm-sniffer/apm-toolkit-activation/apm-toolkit-log4j-2.x-activation/src/main/java/org/apache/skywalking/apm/toolkit/activation/log/log4j/v2/x/async/AsyncLoggerConfigMethodInterceptor.java

public class AsyncLoggerConfigMethodInterceptor implements InstanceMethodsAroundInterceptor {


    @Override
    public void beforeMethod(EnhancedInstance objInst, Method method, Object[] allArguments, Class<?>[] argumentsTypes,
                             MethodInterceptResult result) throws Throwable {
        if (allArguments[0] instanceof EnhancedInstance) {
            EnhancedInstance instances = (EnhancedInstance) allArguments[0];
            instances.setSkyWalkingDynamicField(ContextManager.getGlobalTraceId());
        }
    }

    @Override
    public Object afterMethod(EnhancedInstance objInst, Method method, Object[] allArguments,
                              Class<?>[] argumentsTypes, Object ret) throws Throwable {
        return ret;
    }

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

• AsyncLoggerConfigMethodInterceptor实现了InstanceMethodsAroundInterceptor接口，其beforeMethod方法会将ContextManager.getGlobalTraceId()设置给allArguments[0]的skyWalkingDynamicField

Log4jLogEventInstrumentation

skywalking-6.6.0/apm-sniffer/apm-toolkit-activation/apm-toolkit-log4j-2.x-activation/src/main/java/org/apache/skywalking/apm/toolkit/activation/log/log4j/v2/x/async/Log4jLogEventInstrumentation.java

public class Log4jLogEventInstrumentation 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.toolkit.activation.log.log4j.v2.x.async.Log4jLogEventConstructorInterceptor";
                }
            }
        };
    }

    @Override
    public InstanceMethodsInterceptPoint[] getInstanceMethodsInterceptPoints() {
        return new InstanceMethodsInterceptPoint[0];
    }

    @Override
    protected ClassMatch enhanceClass() {
        return byName("org.apache.logging.log4j.core.impl.Log4jLogEvent");
    }
}

• Log4jLogEventInstrumentation继承了ClassInstanceMethodsEnhancePluginDefine，它使用org.apache.skywalking.apm.toolkit.activation.log.log4j.v2.x.async.Log4jLogEventConstructorInterceptor增强了org.apache.logging.log4j.core.impl.Log4jLogEvent的构造器

Log4jLogEventConstructorInterceptor

skywalking-6.6.0/apm-sniffer/apm-toolkit-activation/apm-toolkit-log4j-2.x-activation/src/main/java/org/apache/skywalking/apm/toolkit/activation/log/log4j/v2/x/async/Log4jLogEventConstructorInterceptor.java

public class Log4jLogEventConstructorInterceptor implements InstanceConstructorInterceptor {

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

• Log4jLogEventConstructorInterceptor实现了InstanceConstructorInterceptor接口，其onConstruct方法目前没有操作

RingBufferLogEventInstrumentation

skywalking-6.6.0/apm-sniffer/apm-toolkit-activation/apm-toolkit-log4j-2.x-activation/src/main/java/org/apache/skywalking/apm/toolkit/activation/log/log4j/v2/x/async/RingBufferLogEventInstrumentation.java

public class RingBufferLogEventInstrumentation extends ClassInstanceMethodsEnhancePluginDefine {
    private static final String INTERCEPT_CLASS = "org.apache.skywalking.apm.toolkit.activation.log.log4j.v2.x.async.RingBufferLogEventMethodInterceptor";
    private static final String ENHANCE_CLASS = "org.apache.logging.log4j.core.async.RingBufferLogEvent";
    private static final String ENHANCE_METHOD = "setMessage";
    @Override
    public ConstructorInterceptPoint[] getConstructorsInterceptPoints() {
        return new ConstructorInterceptPoint[0];
    }

    @Override
    public InstanceMethodsInterceptPoint[] getInstanceMethodsInterceptPoints() {
        return new InstanceMethodsInterceptPoint[]{
            new InstanceMethodsInterceptPoint() {
                @Override
                public ElementMatcher<MethodDescription> getMethodsMatcher() {
                    return named(ENHANCE_METHOD);
                }

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

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

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

• RingBufferLogEventInstrumentation继承了ClassInstanceMethodsEnhancePluginDefine，它使用org.apache.skywalking.apm.toolkit.activation.log.log4j.v2.x.async.RingBufferLogEventMethodInterceptor增强了org.apache.logging.log4j.core.async.RingBufferLogEvent的setMessage方法

RingBufferLogEventMethodInterceptor

skywalking-6.6.0/apm-sniffer/apm-toolkit-activation/apm-toolkit-log4j-2.x-activation/src/main/java/org/apache/skywalking/apm/toolkit/activation/log/log4j/v2/x/async/RingBufferLogEventMethodInterceptor.java

public class RingBufferLogEventMethodInterceptor implements InstanceMethodsAroundInterceptor {


    @Override
    public void beforeMethod(EnhancedInstance objInst, Method method, Object[] allArguments, Class<?>[] argumentsTypes,
                             MethodInterceptResult result) throws Throwable {
        objInst.setSkyWalkingDynamicField(ContextManager.getGlobalTraceId());
    }

    @Override
    public Object afterMethod(EnhancedInstance objInst, Method method, Object[] allArguments,
                              Class<?>[] argumentsTypes, Object ret) throws Throwable {
        return ret;
    }

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

• RingBufferLogEventMethodInterceptor实现了InstanceMethodsAroundInterceptor接口，其beforeMethod方法将ContextManager.getGlobalTraceId()设置给objInst的skyWalkingDynamicField

小结

skywalking的log4j2-activation定义了TraceIdConverterActivation、AsyncLoggerConfigInstrumentation、Log4jLogEventInstrumentation、RingBufferLogEventInstrumentation这几个增强

doc

• TraceIdConverterActivation
• AsyncLoggerConfigInstrumentation
• Log4jLogEventInstrumentation
• RingBufferLogEventInstrumentation