摘要：原文今日生產環境發現有些容器停止響應了，但是容器沒有死，也能正常使用。在容器內部使用發現的一直處于運行狀態但用沒有發現有新的日志輸出，且訪問該應用肯定會輸出日志的接口也是沒有任何日志輸出，因此懷疑阻塞住了。

原文

今日生產環境發現有些容器停止響應了，但是容器沒有死，docker exec -it /bin/bash也能正常使用。

在容器內部使用jstack 發現log4j2的Console Appender一直處于運行狀態：

"AsyncAppender-asyncConsole" #21 daemon prio=5 os_prio=0 tid=0x00007fd968d07000 nid=0x1f runnable [0x00007fd91bffd000]
   java.lang.Thread.State: RUNNABLE
    at java.io.FileOutputStream.writeBytes(Native Method)
    at java.io.FileOutputStream.write(FileOutputStream.java:326)
    at java.io.BufferedOutputStream.write(BufferedOutputStream.java:122)
    - locked <0x00000000f002b408> (a java.io.BufferedOutputStream)
    at java.io.PrintStream.write(PrintStream.java:480)
    - locked <0x00000000f002b3e8> (a java.io.PrintStream)
    at org.apache.logging.log4j.core.util.CloseShieldOutputStream.write(CloseShieldOutputStream.java:53)
    at org.apache.logging.log4j.core.appender.OutputStreamManager.writeToDestination(OutputStreamManager.java:262)
    - locked <0x00000000f021d848> (a org.apache.logging.log4j.core.appender.OutputStreamManager)
    at org.apache.logging.log4j.core.appender.OutputStreamManager.flushBuffer(OutputStreamManager.java:294)
    - locked <0x00000000f021d848> (a org.apache.logging.log4j.core.appender.OutputStreamManager)
    at org.apache.logging.log4j.core.appender.OutputStreamManager.drain(OutputStreamManager.java:351)
    at org.apache.logging.log4j.core.layout.TextEncoderHelper.drainIfByteBufferFull(TextEncoderHelper.java:260)
    - locked <0x00000000f021d848> (a org.apache.logging.log4j.core.appender.OutputStreamManager)
    at org.apache.logging.log4j.core.layout.TextEncoderHelper.writeAndEncodeAsMuchAsPossible(TextEncoderHelper.java:199)
    at org.apache.logging.log4j.core.layout.TextEncoderHelper.encodeChunkedText(TextEncoderHelper.java:159)
    - locked <0x00000000f021d848> (a org.apache.logging.log4j.core.appender.OutputStreamManager)
    at org.apache.logging.log4j.core.layout.TextEncoderHelper.encodeText(TextEncoderHelper.java:58)
    at org.apache.logging.log4j.core.layout.StringBuilderEncoder.encode(StringBuilderEncoder.java:68)
    at org.apache.logging.log4j.core.layout.StringBuilderEncoder.encode(StringBuilderEncoder.java:32)
    at org.apache.logging.log4j.core.layout.PatternLayout.encode(PatternLayout.java:220)
    at org.apache.logging.log4j.core.layout.PatternLayout.encode(PatternLayout.java:58)
    at org.apache.logging.log4j.core.appender.AbstractOutputStreamAppender.directEncodeEvent(AbstractOutputStreamAppender.java:177)
    at org.apache.logging.log4j.core.appender.AbstractOutputStreamAppender.tryAppend(AbstractOutputStreamAppender.java:170)
    at org.apache.logging.log4j.core.appender.AbstractOutputStreamAppender.append(AbstractOutputStreamAppender.java:161)
    at org.apache.logging.log4j.core.config.AppenderControl.tryCallAppender(AppenderControl.java:156)
    at org.apache.logging.log4j.core.config.AppenderControl.callAppender0(AppenderControl.java:129)
    at org.apache.logging.log4j.core.config.AppenderControl.callAppenderPreventRecursion(AppenderControl.java:120)
    at org.apache.logging.log4j.core.config.AppenderControl.callAppender(AppenderControl.java:84)
    at org.apache.logging.log4j.core.appender.AsyncAppender$AsyncThread.callAppenders(AsyncAppender.java:459)
    at org.apache.logging.log4j.core.appender.AsyncAppender$AsyncThread.run(AsyncAppender.java:412)

但用docker logs -f 沒有發現有新的日志輸出，且訪問該應用肯定會輸出日志的接口也是沒有任何日志輸出，因此懷疑log4j2阻塞住了。

Google到有人在log4j提出了類似了問題LOG4J2-2239，官方給出的解釋是問題出在log4j2之外。

于是查一下logback是否也有類似問題，找到LOGBACK-1422，同樣給出的解釋是問題出在logback之外。

兩個問題的共通點都是用docker運行，于是把應用直接進程方式運行，沒有出現問題。

于是Google搜索docker logging to stdout hangs，找到SO的這個回答，以及這個issue，解決方案將Docker升級到18.06。

查看生產環境的docker版本是18.03，升級到18.09后問題解決。