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https://issues.apache.org/jira/browse/LOG4J2-3295?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17466684#comment-17466684
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Ralph Goers commented on LOG4J2-3295:
-------------------------------------
Mike, what you are asking for is simply not possible. Log4j is preventing two
appenders from running simultaneously while both are writing to the same file.
Log4j locks the OutputStream on every write as it cannot know if the underlying
i/o system will block or not. If they don't then two threads writing
simultaneously would corrupt the file. But here you have two output streams
writing to the same file. Under the covers the OS may or may not handle that.
It is not guaranteed. Since there is no way to lock two different OutputStreams
Log4j simply can't allow them to both be open at the same time. If it did you
would possibly be creating a ticket complaining that the files were corrupted
during rollover. You simply cannot have it both ways. Log4j opts to ensure that
the files do not get corrupted.
> Reconfiguration failure with an error
> -------------------------------------
>
> Key: LOG4J2-3295
> URL: https://issues.apache.org/jira/browse/LOG4J2-3295
> Project: Log4j 2
> Issue Type: Bug
> Components: Configuration, Configurators
> Affects Versions: 2.17.0
> Reporter: Mike Li
> Priority: Blocker
>
> Steps to recreate:
> # start with log4j2.xml with following content:
> <?xml version="1.0" encoding="UTF-8"?>
> <Configuration status="DEBUG" monitorInterval="30">
>
> <Appenders>
> <File name="FILE" fileName="c:\temp\product.log">
> <PatternLayout>
> <Pattern>ProductName:%-10p %d\{yyyy-MM-dd HH:mm:ss.SSS}
> {GMT} context:%x [%t] - %-50m - %M(%F:%L)%n</Pattern>
> </PatternLayout>
>
> </File>
> </Appenders>
> <Loggers>
> <Root level="INFO">
> <AppenderRef ref="FILE"/>
> </Root>
> </Loggers>
> </Configuration>
>
> 2. After the application is started and running, edit the log4j2.xml file
> with the following content, notice that the fileName in the WRAP appender is
> the same as that in the original FILE appender.
>
> <?xml version="1.0" encoding="UTF-8"?>
> <Configuration status="DEBUG" monitorInterval="30" >
> <Appenders>
> <Async name="ASYNC" includeLocation="true" bufferSize="4096">
> <AppenderRef ref="WRAP"/>
> </Async>
> <RollingFile name="WRAP" fileName="c:\temp\product.log"
> filePattern="c:\temp\product.log.%i">
> <PatternLayout pattern="ProductName:%-7p %d\{yyyy-MM-dd
> HH:mm:ss.SSS}{GMT}
> context:%x [%t] - %-50m - %M(%F:%L)%n"/>
> <Policies>
> <SizeBasedTriggeringPolicy size="1048576"/>
> </Policies>
> <DefaultRolloverStrategy max="4"/>
> </RollingFile>
> </Appenders>
> <Loggers>
> <Root level="DEBUG">
> <AppenderRef ref="ASYNC"/>
> </Root>
> </Loggers>
> </Configuration>
>
> 3. Wait for the log4j to detect the change in 30 seconds to reconfigure. When
> the reconfigure starts, it reports an error. Here is the exception stack:
>
> 2021-12-28 17:42:41,688 Log4j2-TF-1-ConfiguratonFileWatcher-4 ERROR Could not
> create plugin of type class
> org.apache.logging.log4j.core.appender.RollingFileAppender for element
> RollingFile org.apache.logging.log4j.core.config.ConfigurationException:
> Configuration has multiple incompatible Appenders pointing to the same
> resource 'c:\temp\product.log'
> at
> org.apache.logging.log4j.core.appender.AbstractManager.narrow(AbstractManager.java:169)
> at
> org.apache.logging.log4j.core.appender.rolling.RollingFileManager.getFileManager(RollingFileManager.java:217)
> at
> org.apache.logging.log4j.core.appender.RollingFileAppender$Builder.build(RollingFileAppender.java:146)
> at
> org.apache.logging.log4j.core.appender.RollingFileAppender$Builder.build(RollingFileAppender.java:62)
> at
> org.apache.logging.log4j.core.config.plugins.util.PluginBuilder.build(PluginBuilder.java:122)
> at
> org.apache.logging.log4j.core.config.AbstractConfiguration.createPluginObject(AbstractConfiguration.java:1107)
> at
> org.apache.logging.log4j.core.config.AbstractConfiguration.createConfiguration(AbstractConfiguration.java:1032)
> at
> org.apache.logging.log4j.core.config.AbstractConfiguration.createConfiguration(AbstractConfiguration.java:1024)
> at
> org.apache.logging.log4j.core.config.AbstractConfiguration.doConfigure(AbstractConfiguration.java:643)
> at
> org.apache.logging.log4j.core.config.AbstractConfiguration.initialize(AbstractConfiguration.java:243)
> at
> org.apache.logging.log4j.core.config.AbstractConfiguration.start(AbstractConfiguration.java:289)
> at
> org.apache.logging.log4j.core.LoggerContext.setConfiguration(LoggerContext.java:626)
> at
> org.apache.logging.log4j.core.LoggerContext.onChange(LoggerContext.java:762)
> at
> org.apache.logging.log4j.core.util.AbstractWatcher$ReconfigurationRunnable.run(AbstractWatcher.java:93)
> at java.base/java.lang.Thread.run(Thread.java:831)
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