为什么log4j-slf4j-impl不是锁自由的？

Question

我在我们的应用程序中使用Async log4j2而不是slf4j，我确信这是非阻塞的。但是在集成了BlockHound之后，我得到了一个惊喜：

java.lang.Exception: [worker-1-8] Blocking call: sun.misc.Unsafe#park
 at reactor.blockhound.BlockHound$Builder.lambda$install$6(BlockHound.java:318)
 at reactor.blockhound.BlockHoundRuntime.checkBlocking(BlockHoundRuntime.java:46)
 at sun.misc.Unsafe.park(Unsafe.java)
 at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
 at java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:836)
 at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireQueued(AbstractQueuedSynchronizer.java:870)
 at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquire(AbstractQueuedSynchronizer.java:1199)
 at java.util.concurrent.locks.ReentrantLock$NonfairSync.lock(ReentrantLock.java:209)
 at java.util.concurrent.locks.ReentrantLock.lock(ReentrantLock.java:285)
 at com.lmax.disruptor.TimeoutBlockingWaitStrategy.signalAllWhenBlocking(TimeoutBlockingWaitStrategy.java:62)
 at com.lmax.disruptor.MultiProducerSequencer.publish(MultiProducerSequencer.java:218)
 at com.lmax.disruptor.RingBuffer.translateAndPublish(RingBuffer.java:990)
 at com.lmax.disruptor.RingBuffer.tryPublishEvent(RingBuffer.java:538)
 at org.apache.logging.log4j.core.async.AsyncLoggerConfigDisruptor.tryEnqueue(AsyncLoggerConfigDisruptor.java:392)
 at org.apache.logging.log4j.core.async.AsyncLoggerConfig.logToAsyncDelegate(AsyncLoggerConfig.java:135)
 at org.apache.logging.log4j.core.async.AsyncLoggerConfig.log(AsyncLoggerConfig.java:116)
 at org.apache.logging.log4j.core.config.LoggerConfig.log(LoggerConfig.java:460)
 at org.apache.logging.log4j.core.config.AwaitCompletionReliabilityStrategy.log(AwaitCompletionReliabilityStrategy.java:82)
 at org.apache.logging.log4j.core.Logger.log(Logger.java:162)
 at org.apache.logging.log4j.spi.AbstractLogger.tryLogMessage(AbstractLogger.java:2190)
 at org.apache.logging.log4j.spi.AbstractLogger.logMessageTrackRecursion(AbstractLogger.java:2144)
 at org.apache.logging.log4j.spi.AbstractLogger.logMessageSafely(AbstractLogger.java:2127)
 at org.apache.logging.log4j.spi.AbstractLogger.logMessage(AbstractLogger.java:2020)
 at org.apache.logging.log4j.spi.AbstractLogger.logIfEnabled(AbstractLogger.java:1891)
 at org.apache.logging.slf4j.Log4jLogger.info(Log4jLogger.java:184)

这是意料之中的行为，还是我错过了什么？

Answer 1

Log4j2的异步日志记录只是通过中断器(一种环形缓冲区)将I/O部分传递给单独的线程。生产者使用Java语言内置的notify()向消费者发出信号，它必须获取一个锁。