在java

Question

我正在尝试mdc登录java中的play过滤器，我在scala中按照本教程的所有请求尝试转换为java http://yanns.github.io/blog/2014/05/04/slf4j-mapped-diagnostic-context-mdc-with-play-framework/

但仍然没有将mdc传播到所有执行上下文。 我使用此调度程序作为默认调度程序，但它有许多执行上下文。我需要将mdc传播到所有执行上下文

下面是我的java代码

import java.util.Map;

import org.slf4j.MDC;

import scala.concurrent.ExecutionContext;
import scala.concurrent.duration.Duration;
import scala.concurrent.duration.FiniteDuration;
import akka.dispatch.Dispatcher;
import akka.dispatch.ExecutorServiceFactoryProvider;
import akka.dispatch.MessageDispatcherConfigurator;

public class MDCPropagatingDispatcher extends Dispatcher {
    public MDCPropagatingDispatcher(
            MessageDispatcherConfigurator _configurator, String id,
            int throughput, Duration throughputDeadlineTime,
            ExecutorServiceFactoryProvider executorServiceFactoryProvider,
            FiniteDuration shutdownTimeout) {
        super(_configurator, id, throughput, throughputDeadlineTime,
                executorServiceFactoryProvider, shutdownTimeout);

    }

    @Override
    public ExecutionContext prepare() {
        final Map<String, String> mdcContext = MDC.getCopyOfContextMap();
        return new ExecutionContext() {

            @Override
            public void execute(Runnable r) {
                Map<String, String> oldMDCContext = MDC.getCopyOfContextMap();
                setContextMap(mdcContext);
                try {
                    r.run();
                } finally {
                    setContextMap(oldMDCContext);
                }
            }

            @Override
            public ExecutionContext prepare() {
                return this;
            }

            @Override
            public void reportFailure(Throwable t) {
                play.Logger.info("error occured in dispatcher");
            }

        };
    }

    private void setContextMap(Map<String, String> context) {
        if (context == null) {
            MDC.clear();
        } else {
            play.Logger.info("set context "+ context.toString());
            MDC.setContextMap(context);
        }
    }
}



import java.util.concurrent.TimeUnit;

import scala.concurrent.duration.Duration;
import scala.concurrent.duration.FiniteDuration;

import com.typesafe.config.Config;

import akka.dispatch.DispatcherPrerequisites;
import akka.dispatch.MessageDispatcher;
import akka.dispatch.MessageDispatcherConfigurator;

public class MDCPropagatingDispatcherConfigurator extends
        MessageDispatcherConfigurator {
    private MessageDispatcher instance;

    public MDCPropagatingDispatcherConfigurator(Config config,
            DispatcherPrerequisites prerequisites) {
        super(config, prerequisites);
        Duration throughputDeadlineTime = new FiniteDuration(-1,
                TimeUnit.MILLISECONDS);
        FiniteDuration shutDownDuration = new FiniteDuration(1,
                TimeUnit.MILLISECONDS);
        instance = new MDCPropagatingDispatcher(this, "play.akka.actor.contexts.play-filter-context",
                100, throughputDeadlineTime,
                configureExecutor(), shutDownDuration);
    }

    public MessageDispatcher dispatcher() {
        return instance;
    }

}

过滤器拦截器

public class MdcLogFilter implements EssentialFilter {
@Override
public EssentialAction apply(final EssentialAction next) {
    return new MdcLogAction() {
        @Override
        public Iteratee<byte[], SimpleResult> apply(
                final RequestHeader requestHeader) {
            final String  uuid = Utils.generateRandomUUID();
            MDC.put("uuid", uuid);
            play.Logger.info("request started"+uuid);
            final ExecutionContext playFilterContext = Akka.system()
                    .dispatchers()
                    .lookup("play.akka.actor.contexts.play-custom-filter-context");
            return next.apply(requestHeader).map(
                    new AbstractFunction1<SimpleResult, SimpleResult>() {
                        @Override
                        public SimpleResult apply(SimpleResult simpleResult) {
                            play.Logger.info("request ended"+uuid);
                            MDC.remove("uuid");
                            return simpleResult;
                        }
                    }, playFilterContext);

        }

        @Override
        public EssentialAction apply() {
            return next.apply();
        }
    };
}

}

Answer 1

以下是我的解决方案，在现实生活中得到证实。它在Scala中，而不是Play，但对于Scalatra，但基本概念是相同的。希望您能够弄清楚如何将其移植到Java。

import org.slf4j.MDC
import java.util.{Map => JMap}
import scala.concurrent.{ExecutionContextExecutor, ExecutionContext}

object MDCHttpExecutionContext {

  def fromExecutionContextWithCurrentMDC(delegate: ExecutionContext): ExecutionContextExecutor =
    new MDCHttpExecutionContext(MDC.getCopyOfContextMap(), delegate)
}

class MDCHttpExecutionContext(mdcContext: JMap[String, String], delegate: ExecutionContext)
  extends ExecutionContextExecutor {

  def execute(runnable: Runnable): Unit = {
    val callingThreadMDC = MDC.getCopyOfContextMap()
    delegate.execute(new Runnable {
      def run() {
        val currentThreadMDC = MDC.getCopyOfContextMap()
        setContextMap(callingThreadMDC)
        try {
          runnable.run()
        } finally {
          setContextMap(currentThreadMDC)
        }
      }
    })
  }

  private[this] def setContextMap(context: JMap[String, String]): Unit = {
    Option(context) match {
      case Some(ctx) => {
        MDC.setContextMap(context)
      }
      case None => {
        MDC.clear()
      }
    }
  }

  def reportFailure(t: Throwable): Unit = delegate.reportFailure(t)
}

您必须确保在所有异步调用中使用此ExecutionContext。我通过依赖注入实现了这一点，但有不同的方法。我就是这样做的subcut：

bind[ExecutionContext] idBy BindingIds.GlobalExecutionContext toSingle {
    MDCHttpExecutionContext.fromExecutionContextWithCurrentMDC(
      ExecutionContext.fromExecutorService(
        Executors.newFixedThreadPool(globalThreadPoolSize)
      )
    )
  }

这种方法背后的想法如下。 MDC对属性及其值使用线程本地存储。如果您的单个请求可以在多个线程上运行，那么您需要确保您启动的新线程使用正确的MDC。为此，您需要创建一个自定义执行程序，以确保在开始执行分配给它的任务之前将MDC值正确复制到新线程中。您还必须确保在线程完成任务并继续执行其他操作时，将旧值放入其MDC中，因为池中的线程可以在不同的请求之间切换。