[LOG4J2-880] ConsoleAppender hangs when writing to System.out in a spawned JVM

• Type: Wish
• Status: Open
• Priority: Minor
• Resolution: Unresolved
• Affects Version/s: 2.1
• Component/s: Appenders
• Assignee: Unassigned
• Reporter: Daniel Widdis
• Created: 23/Oct/14 01:55
• Updated: 30/Oct/14 03:40

Description

I am using Log4J2 in an application using Java Parallel Processing Framework (www.jppf.org). One of the features of JPPF is node provisioning, in which a node process can spawn additional JVMs. However, since the spawned JVMs do not have a "console" the only way to access System.out is by redirecting it to a file, which is done automatically.

By default, the ConsoleAppender sets follow="false". However, rather than exiting gracefully doing nothing, it locks an OutputStreamManger and never releases it. This causes the application to hang.

The problem is easily worked around by setting follow="true" on the appender. However, I propose that the default behavior for follow="false" when System.out is unavailable (as in a spawned JVM) should simply return without doing anything, rather than locking resources.

Relevant stack trace of the thread holding the lock is shown below. The writeBytes() method never returned. Other threads attempted to write but were blocked because of this lock.

"pool-5-thread-6" prio=6 tid=0x000000000c0c2000 nid=0x2ce4 runnable [0x000000000d9ae000]
java.lang.Thread.State: RUNNABLE
at java.io.FileOutputStream.writeBytes(Native Method)
at java.io.FileOutputStream.write(Unknown Source)
at java.io.BufferedOutputStream.write(Unknown Source)

• locked <0x00000000d0063960> (a java.io.BufferedOutputStream)
  at java.io.PrintStream.write(Unknown Source)
• locked <0x00000000d0063940> (a java.io.PrintStream)
  at org.apache.logging.log4j.core.appender.OutputStreamManager.write(OutputStreamManager.java:122)
• locked <0x00000000d00638e0> (a org.apache.logging.log4j.core.appender.OutputStreamManager)
  at org.apache.logging.log4j.core.appender.OutputStreamManager.write(OutputStreamManager.java:136)
  at org.apache.logging.log4j.core.appender.AbstractOutputStreamAppender.append(AbstractOutputStreamAppender.java:106)
  at org.apache.logging.log4j.core.config.AppenderControl.callAppender(AppenderControl.java:97)
  at org.apache.logging.log4j.core.config.LoggerConfig.callAppenders(LoggerConfig.java:428)
  at org.apache.logging.log4j.core.config.LoggerConfig.log(LoggerConfig.java:407)
  at org.apache.logging.log4j.core.config.LoggerConfig.log(LoggerConfig.java:410)
  at org.apache.logging.log4j.core.config.LoggerConfig.log(LoggerConfig.java:365)
  at org.apache.logging.log4j.core.Logger.logMessage(Logger.java:112)
  at org.apache.logging.log4j.spi.AbstractLogger.logMessage(AbstractLogger.java:1336)
  at org.apache.logging.log4j.spi.AbstractLogger.logIfEnabled(AbstractLogger.java:1325)
  at org.apache.logging.log4j.spi.AbstractLogger.warn(AbstractLogger.java:1738)